Why 100& (Long)
Scott
Scott
Larry "Harris" Taylor <dive...@earthlink.net> wrote in message
news:jWhN5.22688$Pw6.1...@newsread1.prod.itd.earthlink.net...
> Why 100%
> by
> Larry "Harris" Taylor, Ph.D.
>
> This material is copyrighted and the author retains all rights. This
> material is made available as a service to the diving community by the
> author and may be distributed for any non-commercial or Not-For-Profit
use.
> This paper is based on the author's DAN O2 Provider Class.
>
> The ability of oxygen to relieve the symptoms of decompression illness
> (Caisson's Disease) has been known since the mid 1800's. The use of oxygen
> by recreational divers as a first aid measure has been promoted for more
> than three decades. A training organization, DAN, was founded in the US
with
> a primary goal of getting the message of on-site O2 delivery to the
> recreational community. Yet, despite all the effort of the recreational
> educational community, there is still a major lack of understanding in
> recreational divers for the need to deliver the highest possible O2
> concentration to the victim of a diving accident malady. Perhaps, this
stems
> from a lack of understanding of the reason behind the hyperbaric medical
> community's recommendation for 100% O2 to be delivered to a diving
accident
> victim.
>
> A diving malady, from a simplistic point of view, can be envisioned
> primarily as a "bubble disorder." A bubble of inert (not used in body
> metabolism, so it accumulates) gas has formed in the body. This bubble may
> impede nerve impulses, block circulation, or trigger a variety of cellular
> processes designed to cope with foreign-to-the-body molecular invaders.
The
> symptoms seen in the victim will depend on how much gas has formed bubbles
> and where these bubbles are located. Our mission, at the first responder
> level, is to reduce, as much as possible, the magnitude of this "bubble
> trouble." An understanding of simple gas dynamics gives us the rationale
> for the need for 100% oxygen delivered to meet the full respiratory needs
of
> the patient.
>
> From a standpoint of "molecular psychology," gas molecules tend to ignore
> the presence of other types of gas and focus only on their own kind. Each
> element or compound present in the gaseous state will act independently,
as
> if they were alone. (So, the total (Dalton's Law of Partial Pressure)
> pressure observed is the sum of all gas components present). If a
> gas-permeable barrier (like a cell wall of the interface between a liquid
> and a gas) is introduced into the system, then each gas will independently
> try, in terms of "molecular sociology," to acquire the same concentration
of
> their type on both sides of this barrier. Gas molecules will freely move
in
> both directions across the barrier, but the net movement (into or out of)
> the gas pocket surrounded by a barrier will be directed towards making the
> concentration the same on both sides. The movement of each gas type will
be
> primarily dictated by the DIFFERENCE in concentrations between inside and
> outside for each type of gas present.
>
> So, let's consider a nitrogen (or any inert gas in the breathing mix)
bubble
> inside a diver. The body's chemical machinery cannot utilize the gas, so
it
> just accumulates and interferes with normal body processes. If we want to
> "denitrogenate" (get rid of the offending inert gas bubble) the body, we
> must introduce an environment that contains NO NITROGEN (or whatever gas
was
> used as the inert gas in the breathing mix). We could use ANY gas that was
> NOT nitrogen, Anything! Carbon monoxide, hydrogen cyanide, argon, or
methane
> would do the job. (Remember, ANY gas that is NOT nitrogen will result in a
> net movement of Nitrogen FROM the bubble) Of course, the gasses just
> mentioned are toxic to life, and, if unused by the body, would themselves,
> accumulate., so it is probably best that we do not use them. Instead
> consider oxygen.
>
> If we surround the offending nitrogen bubble with a ZERO nitrogen
> concentration by introducing 100% oxygen environment, we give rise to the
> following scenario:
>
> O2 === > (Bubble) === > N2
>
> In terms of "molecular sociology:" at time zero;
>
> 1. There is no N2 "outside" bubble, so N2 moves out in an attempt to
> equalize concentrations
> 2. There is no O2 "inside," so it moves into the bubble.
>
> Eventually, (from a very simplistic point of view), the N2 moves outside
and
> the O2 moves inside so, the bubble is composed primarily of O2. But, the
> body chemistry can consume O2, Thus, the bubble disappears. Microscopic
> examination of "bent" animal tissue surrounded by a 100% O2 atmosphere
has
> shown that the bubbles shrink and disappear from view in about 2 hours.
>
> Why all the hype about 100% ?
>
> The rate of gas movement out of the bubble is primarily determined by
> concentration of inert gas on the outside of the bubble. ANY NITROGEN IN
THE
> BREATHING MIX WILL SLOW DOWN THE REMOVAL OF NITROGEN FROM THE BODY!
>
> The best possible first responder scenario is for the patient for them to
> breathe 100% O2. This promotes "denitorgnation," assists in delivering O2
to
> hypoxic tissues and dramatically reduces brain edema.
>
> Most oxygen delivery equipment is meant to deliver lower than 100% O2.
This
> is because most O2 delivery equipment is DESIGNED to treat
shock-associated
> hypoxia that occurs from trauma or disease. This is NOT the same as using
O2
> to "denitrogenate!"
>
> In diving, since our mission is primarily to "denitroginate," our O2
> delivery devices MUST address this need. That is why devices that deliver
> 100% O2 are considered the "best" devices for treating a diving malady and
> should be the delivery device of choice in the on-site first responder
> management of a dive malady.
>
>
> References on bubble shrinkage:
>
> Hydlegarrd, O. & Madsen, J. Influence Of Helox, Oxygen and N2O-O2
Breathing
> On N2 Bubbles In Adipose Tissue, Und. Biomed. Res. 16(3), 1989, 183-193.
>
> Hyldegarrd, O. Moller, M. & Madsen, J. Effect of He-O2, O2, and N20-O2
> Breathing On Injected Bubbles In Spinal White Matter, Und. Biomed. Res.
> 18,(5-6), 1991, 361-371.
>
> Hyldegarrd, O. Moller, M. & Madsen, J. Protective Effect Of Oxygen And
> Heliox Breathing During Development Of Spinal Decompression Sickness, Und.
> Biomed. Res. 21,(2), 1994, 115-128.
>
> Hydlegarrd, O. & Madsen, J, Effect Of Air, Heliox, And Oxygen Breathing On
> Air Bubbles In Aqueous Tissues In The Rat, Und. Biomed. Res. 21(4), 1994,
> 423-424.
>
>
>
>
> About the author:
>
> Larry "Harris" Taylor, Ph.D. is a biochemist and scuba instructor at the
> University of Michigan.
> He has authored more than 100 scuba related articles. His personal dive
> library (See Alert Diver,
> Mar/Apr,1997, p. 54) is considered by many as one of the best recreational
> sources of information in North America.
>
>
>
Iain Smith
>equalize concentrations
>2. There is no O2 "inside," so it moves into the bubble.
The initial movement of O2 into the bubble is faster than the movement out
of N2. This causes the bubble to grow, until sufficient N2 is released. This
presents as a transient worsening of the condition. Any casualty should be
warned in advance about this, and reassured that it is normal.
Another benefit of pure O2 is that a higher ppO2 will result in increased
diffusion of O2 into the tissue whose blood supply has been compromised. The
higher the ppO2, the further the diffusion (or the greater the ppO2 at any
given distance from the non-compromised supply). In other words, 100% O2 is
the best possible treatment for hypoxic tissue.
Iain
Steven B. Harris
"Iain Smith" <iainm...@btinternet.com> wrote:
>>1. There is no N2 "outside" bubble, so N2 moves out in an attempt to
>>equalize concentrations
>>2. There is no O2 "inside," so it moves into the bubble.
>
>
>The initial movement of O2 into the bubble is faster than the movement
out
>of N2. This causes the bubble to grow, until sufficient N2 is released.
This
>presents as a transient worsening of the condition. Any casualty should
be
>warned in advance about this, and reassured that it is normal.
Right. "Mr. Jones, here's some oxygen. You legs will get more numb,
but this is expected and normal, okay?"
>Another benefit of pure O2 is that a higher ppO2 will result in
>increased diffusion of O2 into the tissue whose blood supply has been
>compromised. The higher the ppO2, the further the diffusion (or the
>greater the ppO2 at any given distance from the non-compromised
>supply). In other words, 100% O2 is the best possible treatment for
>hypoxic tissue.
Well, no. There's not a lot of evidence for that, and in the brain and
CNS, there's some evidence against. People have tried resuscitating
animals on higher ppO2s, and if anything the outcomes are worse on
reperfusion.
One problem is that any such effect in the CNS in any direction, will be
is a small one. Blood with a 600 Torr/0.8atm ppO2 (about what you see on
100% 02) contains only 4% more O2 content or so than blood at normal
ppO2. It only takes a tiny bit of O2 depletion to drop the ppO2 of that
blood all the way back into normal physiologic range, so it really
doesn't influence tissue gradients very much in hypoxic tissues with a
lot of demand, in which a lot of utilization is taking place (like your
brain). It does raise tissue ppO2 transiently (30 min to an hour or so)
in hypoxic and poorly perfused tissues with low O2 use (a good example
would be a tumor undergoing irradiation). But that kind of thing is not
where it's needed in DCS.
I can't disagree that 100% O2 is the treatment of choice on a boat for
DCS, but the reason is bubble reduction, and that's it. The rest is
theoretical BS, and (even worse) it isn't true.
Rich Lesperance
Larry "Harris" Taylor <dive...@earthlink.net> wrote:
Thanks, Harris, I was beginning to feel outnumbered in the 80/20 debate <g>.
Rich L
Rich Lesperance
Larry "Harris" Taylor <dive...@earthlink.net>
> 80/20 is a VERY GOOD choice as an in-water deco mix 'cause it
I find myself rather surprised at hearing this from you. Hopefully, we can
discuss this intelligently....
I must strongly disagree with your statement.
> 1. has about the same in-water time obligation as 100% O2 while incurring
> less O2 toxicity unit build-up
> (in-water uses weight of water column to boost pO2 ...
ppO2 of 80/20 at 30 feet is 1.53
ppO2 of 100% at 20 ft is 1.61
So it's not even equivalent.
And while you're at 30 feet breathing 80/20, you are inspiring a ppN2 of 0.4
ata.
You are deliberately adding nitrogen to a gas designed to assist you in
off-gassing nitrogen?
> But
> expedition diving operates under different rules than typical open water
> recreational activity.
Granted, so I will not address that. Only single or single repet deco
diving.
> 2. avoids any possible hassles with the FDA 'cause the law specifically
> defines requirements for transfilling 100% O2 cylinders (in US, 100% O2
> transfilling stations MUST be FDA licensed to legally fill 100% O2
> containing cylinders for human consumption ... unlicensed filling 100% O2
> cylinders for human consumption is, under strict interpretation of FDA
> guidelines, a felony ..see FDA guidelines on Medical Gases)
Well, if this is true, it is more honored in the breach.
How are you going to get your 80/20? Is there any other method besides
partial pressure filling? I've never heard of a membrane that can go that
high... The welding supply shop, or wherever you get your O2, is only going
to have 100% banked....
So 80/20 is subject to the same non-enforcement of regulations that 100% is.
> Bubble reduction is dependent on concentration gradients and is NOT a
linear
> function .... 80% is simply NOT as effective as 100 % and all the ranting
> and raving will not alter this reality.
Agreed, and the physiology holds as well at 20 feet as it does at zero.
80/20 is simply NOT as effective as 100% as a deco gas.
I, and every diver I know, uses 100% O2 for deco. To date, the number of
problems caused by lung toxicity: ZERO.
But of course, I don't do dives where I spend more than a total of ~30
minutes at 20 feet on deco, so like I said, this is not considered
"expedition" diving.
But the WKPP world record divers, with six hour bottom times and twelve
hours of deco, use only 100%, and they have reported no problems, either.
> 2. If you are in a leadership role, then using less than 100% O2 by demand
> inhalator is giving the potential plaintiff an opening big enough to sail
a
> 1000 foot freighter through. This potentially puts your livelihood for the
> rest of your life at risk.
This is defensive medicine. The other reasons (for using 100% on the
surface) are justification enough.
You have not, however, provided a rationale for using 80/20 on deco. Tom
Mount admitted he started having his students breathe it because they had
problems maintaining buoyancy control at their 20 foot stop. Any
physiological reasons seem to be rearwards justification.
Rich L
Michael J. Blitch
<dive...@earthlink.net> wrote:
>Why 100%
>by
>Larry "Harris" Taylor, Ph.D.
Thank you for the simplistic explanation. While I don't think anyone
would argue the value of 100% over 80/20 on the surface, do you want
to get into the vlaue of the same gasses for deco underwater?
Also, hopefully now that I have your attention, do you have references
concerning the overfilled tank and DOT regulations of federal 'law'?
Sorry to have asked if you have already responded.
--
Things I'd Do If I Ever Became An Evil Overlord:
175: I will have my fortress exorcized regularly. Although ghosts in the dungeon provide an appropriate atmosphere, they tend to provide valuable information once placated.
Steven B. Harris
"Rich Lesperance" <ri...@ufl.edu> wrote:
>>
>How are you going to get your 80/20? Is there any other method besides
>partial pressure filling? I've never heard of a membrane that can go
that
>high... The welding supply shop, or wherever you get your O2, is only
going
>to have 100% banked....
Not at all. Your average dive shop which mixes nitrox does it with
prefilled large cylinders of medical grade 80/20. That allows them to
get around the FDA rules for dispensing 100%. So far as this goes, 80/20
is just one more EAN. Whereas 100% O2 is a whole other animal.
The welding shop may have 100%, but it's not a grade permitted for human
use.
>So 80/20 is subject to the same non-enforcement of regulations that
>100% is.
Nope
>>I, and every diver I know, uses 100% O2 for deco. To date, the number
of
>problems caused by lung toxicity: ZERO.
>
>But of course, I don't do dives where I spend more than a total of ~30
>minutes at 20 feet on deco, so like I said, this is not considered
>"expedition" diving.
OTU systemic toxicity units are classically monitored by seeing how much
ppO2 for how long it takes to give you enough bronchitis to lower your
maximal expiratory ventilation by 5%. This is reversable, same as any
lung hit, and you probably wouldn't feel it. And you can go much farther
if you're doing on expeditionary cave diver every few months, or longer.
You can't keep doing that kind of hit every week, however, or even a
couple of times a month. It gets to feeling like asthma or a smoker's
cough.
Bottom line is the WKPP can get away with a lot more systemic OTU at 1.6
ata than the diver doing some deco with 100% O2 several times a month.
>
> But the WKPP world record divers, with six hour bottom times and
>twelve
>hours of deco, use only 100%, and they have reported no problems,
>either.
See above. You can do a lot to yourself if you spend a year preparing
for one of these, and months afterword writing about it congratulating
yourself about it. The rest of us would like to go diving.
>You have not, however, provided a rationale for using 80/20 on deco.
Tom
>Mount admitted he started having his students breathe it because they
had
>problems maintaining buoyancy control at their 20 foot stop. Any
>physiological reasons seem to be rearwards justification.
Whatever Tom Mount used it for is irrelevent.
Also rather inexplicable is Irvine and his rants about how 80/20 at 10
feet gives a ppO2 of 1.04 ata, which he says is "worthless for deco."
Well if it is, it's the same pp02 as his 50/50 gives him at 30 feet. But
he uses 50/50 up to switching to 100% at 20 ft. It's the same argument
either way, sauce for the goose is sauce for the gander. Apparently 1.04
ata is worthless when something else passes through it at 10 ft, but a
tolerated staging oxygen rest when Irvine does it at 30 ft.
SBH.
PS. One thing I've yet to see is a deliberate time of 100% O2 breathing
at the surface as part of a deco plan. It's a hell of a lot easier than
doing it in-water (since you have all the gas you like without having
to carry it, and can even get a backrub while doing it). And it's
clearly not "worthless," because it's the same treatment DAN uses for
the bends. If it works for the bends, it will work as part of deco to
prevent bends. So why not plan for it?
I can only conclude that it's not done because somebody hasn't really
thought about doing it. The mindset (except in the Navy obviously) is
that your dive is terminated when you hit the surface, and any oxygen
administered after that should only be done to treat symptoms.
Stupid.
Popeye
>Not at all. Your average dive shop which mixes nitrox does it with
>prefilled large cylinders of medical grade 80/20. That allows them to
>get around the FDA rules for dispensing 100%. So far as this goes, 80/20
>is just one more EAN. Whereas 100% O2 is a whole other animal.
>
>The welding shop may have 100%, but it's not a grade permitted for human
>use.
>
Steve, I've never seen this, the five dive shops I fill at use 100% O2.
I'm a certified blender and have done thousands of PP fills, and scores of
100% fills.
Popeye
Drink and be merry, for life
is short, and death lasts forever.
Randy F. Milak
>
> In article <8u58fd$121i$2...@spnode25.nerdc.ufl.edu>,
> "Rich Lesperance" <ri...@ufl.edu> wrote:
> >
> > How are you going to get your 80/20? Is there any other method besides
> > partial pressure filling? I've never heard of a membrane that can go
> > that high... The welding supply shop, or wherever you get your O2, is
> > only going to have 100% banked....
>
> Not at all. Your average dive shop which mixes nitrox does it with
> prefilled large cylinders of medical grade 80/20. That allows them to
> get around the FDA rules for dispensing 100%. So far as this goes, 80/20
> is just one more EAN. Whereas 100% O2 is a whole other animal.
>
> The welding shop may have 100%, but it's not a grade permitted for human
> use.
I would suggest, that oxygen is oxygen is oxygen. The filling
process and dew point are the only differences in the three grades; that
being aviation, medical and industrial; with aviation grade having the
lowest dew point.
> > I, and every diver I know, uses 100% O2 for deco. To date, the number
> > of problems caused by lung toxicity: ZERO...
> Bottom line is the WKPP can get away with a lot more systemic OTU at 1.6
> ata than the diver doing some deco with 100% O2 several times a month.
I assume the inference is, that an individual's tolerance to
pulmonary oxygen toxicity would be greater, the less they are exposed to
a hyperoxic event prior to a staged decompression dive; compared with a
diver, whom, conducts staged, oxygen decompressions, several times a
month? Perhaps so during long, O2 exposure, repetitive (within 24
hours) diving; but unlikely to be problematic outside of that event
schedule. I would suggest that the percentage of vital capacity
decrement (%Vc) be examined more closely, as a diver with an exposure of
1425 UPTD for example, can be re-exposed in as little as 12 hours with
little to no residual pulmonary distress.
> PS. One thing I've yet to see is a deliberate time of 100% O2 breathing
> at the surface as part of a deco plan. It's a hell of a lot easier than
> doing it in-water (since you have all the gas you like without having
> to carry it, and can even get a backrub while doing it). And it's
> clearly not "worthless," because it's the same treatment DAN uses for
> the bends. If it works for the bends, it will work as part of deco to
> prevent bends. So why not plan for it?
>
> I can only conclude that it's not done because somebody hasn't really
> thought about doing it. The mindset (except in the Navy obviously) is
> that your dive is terminated when you hit the surface, and any oxygen
> administered after that should only be done to treat symptoms.
Oxygen, used as a post dive prevention of DCS is very common among
staged decompression divers. Has been for some years.
--
Randy F. Milak
Windsor, Ontario
~Rig for silent running. Aye sir, All ahead lurk...~
Randy F. Milak
>
> I had really hoped to avoid this ...
<G>.
> I sort of had the urge to write again ...
Great, keep it up. Everyone enjoys your articles (whether they agree or
not is another matter <g>).
> The primary reason, as I inderstand it, for lowering O2 concentration
> is NOT related to offgassing nor bouyancy control ...there is NOT much
> difference (as I stated) in "typical" in-water deco time for 100% vs
> 80 % (some times, dependant on profile, just a few minutes). This
> means there is only a small in-water time penalty to be paid for using
> a lower concentration mix. But the differnces in pulmonary toxicity
> (also a distinctly non-linear function) unit accumulation (otu's) can
> be significant. This is especially something to be considered in
> expedition type diving.
Very, very true. Consider the following...
Exiting the water asymptotic, is the primary objective of any
staged decompression strategy. Within that strategy, one tries to
egress the water as quickly as possible, while maintaining the primary
objective.
Time is often seemingly paradoxical in diving. Time at depth isn't
the problem; the absence of sufficient time spent for an
appropriate, applicable staged decompression is. Time is a luxury
underwater. We unfortunately, have a finite supply of gas; thermal
considerations over time, etc., so we can't afford a bounty of time to
decompress in the water. Time is therefore, the primary focus, of a
sound decompression strategy. Minimize the decompression requirements,
whilst affording an asymptotic egress -- win, win.
In order to decompress, one must reduce ambient pressure of course;
and that's where the problem lies. How to reduce, eliminate or prevent
the inert gas in tissue, from causing overt, symptomatic DCS upon
reduction of ambient pressure? One must look for methodologies, or
strategies if you wish, to achieve the latter. Several strategies are
found in the study of gas kinetics itself.
Oxygen provides for an ideal offgassing gradient of high to low
inert gas partial pressures. The higher the PO2, the more efficient the
offgassing. So why don't we utilize 100% oxygen as the ONLY gas to be
used for diving and forget about everything else? Oxygen toxicity of
course.
Oxygen has limits; points of diminishing return to where the offgas
benefit is outweighed by its toxicity effects. A fundamental
decompression strategy is to "buffer" the oxygen with an inert gas
(usually nitrogen) so that one can gain the best of oxygen's
benefits (increased PO2s) while reducing its toxic effects.
The pulmonary effects of hyperoxia include desiccation of the
mucous membranes, depression of ventilation, vasodilatation of the
pulmonary vasculature, and absorption atelectasis. A P02 is a P02
regardless and the OTU and UPTD counts may be similar for either 100% 02
deco or for 80/20 deco given similar PO2 exposures. However, little
known to many divers, is a condition known as absorption atelectasis
which is an abnormal condition with the collapse of lung tissue. This
prevents the exchange of CO2 and O2 by the blood. It occurs with
exposure to 100% oxygen, however, it can be prevented by limiting the
delivered fractional inspired oxygen (FiO2) level to 0.95 or less,
thereby providing at least 5% nitrogen in the inspired gas (1,2). 80/20
mixes, do not require "air/lower FO2" breaks (the buffer is already in
the mix); as such, eliminates unnecessary gas switching (important in
cold water), and the PO2 remains relatively constant. Therefore, to
reemphasize Harris's statement, an 80/20 mix suffers only a small
in-water time penalty to be paid, but the significant reduction in
pulmonary toxicity exposure can be significant.
Its been suggested that a diver is "deliberately adding nitrogen to
a gas designed to assist you in offgassing nitrogen?" Perhaps implying
that the diver is still ongassing the N2. The gas loading derived from
a PN2 0.18 is insignificant and nearly theoretically impossible to ongas
in a staged decompression situation. It's below the ambient PN2
experienced on the surface of the earth. It can not effect a saturated
or supersaturated tissue. It is unlikely that any tissue had or has a
PN2 of less then 0.18, prior to or during the dive. Therefore that PN2
is still allowing for offgassing, not gas loading. Therefore the PN2 of
an 80/20 mix, used at an appropriate MOD is insignificant to the
decompression.
However in certain cases, counterdiffusion can occur to the degree
where the total inert gas pressure in the tissue is less than the
surrounding ambient pressure (there does not have to be a critical
gradient). This process actually works to shorten the decompression
time. We "stage" gases for this reason.
The same situation exists during gas switching from a high fraction
of helium (FHe) bottom mix, to any EAN as well. The decompression
obligation can be significantly reduced by switching to EAN as deep as
safely practical because the helium (2.65 times faster than nitrogen) is
offgassing rapidly while nitrogen is ongassing more slowly. Helium, for
example, will begin to offgas immediately after a switch to another gas
with less or no helium, even at a constant depth. The diver will begin
to offgas immediately after any gas switch, from a lower to higher FO2,
except with EAN 80, the benefit is derived, faster within the
decompression regime and 10' deeper than that of 100% oxygen.
It should be noted, the reverse process of switching from a heavier
inert gas to a lighter inert gas (i.e. nitrogen to helium) can create a
supersaturated condition, where the tissue inert gas pressure is greater
than the ambient inert gas pressure, even with no change in ambient
pressure (i.e. depth) from the switch. The phenomenon is termed deep
isobaric supersaturation; caused by counterdiffusion.
Therefore, optimum PO2 is a major factor in decompression. Oxygen
provides for an ideal offgassing gradient of high to low inert gas
partial pressures. Since 100% oxygen cannot be utilized throughout
decompression due to cytotoxic concerns, an inert gas must be used
(nitrogen most notably). It is the sequencing of these gases bound by
counterdiffusion that stages the decompression regime. Special
consideration must be given to the sequencing of gases throughout the
decompression to allow for optimum PO2 and inert gas counterdiffusion to
be used as an advantage, not a liability. Asymptomatic decompression,
less oxygen toxicity risk with only a minor sacrifice in deco time spell
WIN-WIN.
--
Randy F. Milak
Windsor, Ontario
~Rig for silent running. Aye sir, All ahead lurk...~
(1) Neuman TS. Pulmonary Disorders in Diving. Chapter 20 in: Bove AA,
Davis JC; Diving Medicine, 2nd Edition, W.B. Saunders Co., Philadelphia,
1990.
(2) Fox RB, Hoidal JR, Brown DM, et al. Pulmonary inflamation due to
oxygen toxicity: Involvement of chemotactic factors and
polymorphonuclear leukocytes. Am Rev Respir Dis 1981; 123: 521.
Steven B. Harris
buzcu...@aol.com (Popeye) wrote:
>>
>>Not at all. Your average dive shop which mixes nitrox does it with
>>prefilled large cylinders of medical grade 80/20. That allows them to
>>get around the FDA rules for dispensing 100%. So far as this goes,
80/20
>>is just one more EAN. Whereas 100% O2 is a whole other animal.
>>
>>The welding shop may have 100%, but it's not a grade permitted for
human
>>use.
>>
>
> Steve, I've never seen this, the five dive shops I fill at use 100%
O2.
>
> I'm a certified blender and have done thousands of PP fills, and
scores of
>100% fills.
Perhaps illegally? The FDA stuff is fed, of course. In California, for
whatever reason, you'll see the O2 shipped in as big racks of 80/20.
I.M. Smith
> >warned in advance about this, and reassured that it is normal.
>
> Right. "Mr. Jones, here's some oxygen. You legs will get more numb,
> but this is expected and normal, okay?"
"...and it will pass very quickly."
MUCH better than, "Mr. Jones, here's some O2 for your bend".
"Dr. Harris, Dr. Harris! I'm feeling worse. Your damned oxygen has made
me worse. I'm not having any more of it!"
As for the remainder, could you point me in the direction of some
references. What I posted was what I was taught, what is in my
instructor notes, and appears logical. I would, in all seriousness, be
very interested to find out more about your comments that the effect
described is BS and doesn't exist.
Iain
Popeye
>scores of
>>100% fills.
>
>
>
>Perhaps illegally? The FDA stuff is fed, of course. In California, for
>whatever reason, you'll see the O2 shipped in as big racks of 80/20.
>
Steve, you may be correct. But I have taken three Nitrox courses and two
blender courses, and never heard this mentioned. 100% O2 fills are common for
deco bottles around here, and in S. Fla.
Popeye
5 Bucks on Team 3
Randy F. Milak
With respect to bubble growth, the following was described:
"The initial movement of O2 into the bubble is faster than the movement
out of N2. This causes the bubble to grow, until sufficient N2 is
released. This presents as a transient worsening of the condition. Any
casualty should be warned in advance about this, and reassured that it
is normal."
In absolute pressure units, the corresponding critical gradient, G
= Q - P , is related to ambient pressure, P, and critical inert gas
pressure, M, with Q = 1.27 M . Q is the saturation curve relating to
permissible gas tension. In bubble theories, supersaturation is limited
by the critical gradient, G (G values). If the tissue tension of gas
is greater than the bubble, G is positive, leading to bubble growth.
The bubble shrinks once the tissue has offgassed sufficiently for the
tension of the inert gas to fall below the bubble pressure.
According to Vann et al (1), the partial pressure gradient across
the bubble surface is G = T - Pb, where T is tissue tension and Pb is
the pressure inside the bubble. G is positive if partial tissue
tension exceeds bubble partial pressure, causing bubble growth. G is
negative if bubble pressure exceeds tissue tension causing bubble
shrinkage. The magnitude of a negative G is essentially a measure of the
oxygen window.
Therefore, 'bubble' can be expected to increase in size during the
initial administration of O2; and it could be reasonable to assume that
any increase in bubble size may cause increased discomfort for the diver
suffering DCS. Simply, 'it may get worse, before it ever gets better'
appears concessive.
With respect to high PO2s increasing oxygen , the following was
described:
"Another benefit of pure O2 is that a higher ppO2 will result in
increased diffusion of O2 into the tissue whose blood supply has been
compromised. The higher the ppO2, the further the diffusion (or the
greater the ppO2 at any given distance from the non-compromised
supply). In other words, 100% O2 is the best possible treatment for
hypoxic tissue."
Diffusion is the intermingling of gas molecules with tissue, and is
the mechanism by which a gas will saturate and desaturate tissue.
Diffusing capacity (diffusivity) is the ability of gas to pass through a
permeable membrane, as the ability of oxygen to enter blood cells for
example. It's measured in terms of unit area and the pressure
difference on the two sides of the membrane. Keep in mind that
*Perfusion* is the permeation of dissolved gas through tissue.
Perfusion is the limiting factor. Perfusion is the distance the gas
must travel from the tissue to a blood vessel. The greater the distance
the dissolved gas must travel to a blood vessel, the slower the
perfusion rate. Perfusion can vary by type of tissue (ie. none for the
cornea of the eye; high for all nerve and brain tissue), or by activity
(less perfusion for muscles at rest than for muscles exercising).
The control of tissue perfusion resides within the microvasculature
itself. The microvasculature is composed of arterioles, capillaries,
and postcapillary venules. Precapillary sphincter muscles regulate the
flow of blood through capillaries.
As RBCs travel the capillaries, oxygen dissociates from
oxyhemoglobin and diffuses into the tissues. Transport of O2 from the
capillaries to the cells is a direct function of the oxygen needs of the
tissues and the diffusion distance from the capillaries to the
mitochondria as described previously (2,3). The diffusion distance in
turn depends on the number of perfused capillaries and their
arrangement within the tissue. The range of diffusion distances from
capillary to the mitochondria varies for 50 µm in resting muscle to less
than 10 µm in contracting muscle (4).
Oxygen, especially hyperbaric O2 therapy treats diseases caused by
ischemia (oxygen starvation in tissues) with a phenomenal increase of
oxygen into the blood circulation. Breathing 100% oxygen at pressures
of 2.4 to 3.0 atmospheres absolute increases P02 to 1 100 to 1 900 mmHg
(millimeters of mercury) respectively, and increases dissolved oxygen in
plasma by about 20 fold, thereby directly delivering adequate oxygen to
compromised, hypoxic tissues (5,6). Any increase in PO2 will have a
beneficial effect. Therefore, as to this being "theoretical BS", I
would suggest otherwise.
--
Randy F. Milak
Windsor, Ontario
~Rig for silent running. Aye sir, All ahead lurk...~
(1) R.D. Vann and E.D. Thalmann in The Physiology and Medicine of
Diving. 4th edition, P. Bennett and D. Elliot, Eds.
(2) Cole RP, Sukanek PC, Wittenberg JB, et al. Mitochondrial function in
the presence of myoglobin. J Appl Physiol 1983;53: 1116-1124.
(3) Ellsworth ML, Pittman RN. Heterogeneity of oxygen diffusion through
hamster striated muschles. Am J Phsiol 1984;246: 161-167.
(4) Hansson-Mild K, Linderholm H. Some factors of significance for
respiratory gas exchange in muscle tissue. Acta Physiol Scand 1984;112:
395-404.
(5) Mathieu D, Wattel F, Bouachour G, Billard V, Defoin JF. Post
traumatic limb ischemia: prediction of final outcome by transcutaneous
oxygen measurements in hyperbaric oxygen. J Trauma 1990; 30:307-314.
(6) Sheffield PF. Tissue oxygen measurements. In: Davis JC, Hunt TK,
eds. Problem wounds: the role of oxygen. New York: Elsevier Publishing,
1988:46-47.
I.M. Smith
> Let me add two more things your blending course should have mentioned:
>
> 1. Special bulletin 107 from the CGA specifically advises against taking
> 100% O2 cylinders underwater. This was issued as a result of explosions that
> occurred in filling steel O2 tanks that had been submerged.
> (salt water and high pO2 promote rapid corrosion)
Another argument for using AL deco bottles? It strikes me that advising
against ALL O2 cylinders on the basis of explosions in steel bottles
would be like requiring VIP+ for steel cylinders because of problems
with AL ones. (and any dive shop owners out there - don't even THINK
about it! :-) )
Randy F. Milak
has truncated my original post, Thanks
Larry \"Harris\" Taylor wrote:
>
> I had really hoped to avoid this ...
<G>.
> I sort of had the urge to write again ...
Great, keep it up. Everyone enjoys your articles (whether they agree or
not is another matter <g>).
> The primary reason, as I inderstand it, for lowering O2 concentration
> is NOT related to offgassing nor bouyancy control ...there is NOT much
> difference (as I stated) in "typical" in-water deco time for 100% vs
> 80 % (some times, dependant on profile, just a few minutes). This
> means there is only a small in-water time penalty to be paid for using
> a lower concentration mix. But the differnces in pulmonary toxicity
> (also a distinctly non-linear function) unit accumulation (otu's) can
> be significant. This is especially something to be considered in
> expedition type diving.
Very, very true. Consider the following...
Exiting the water asymptomatic, is the primary objective of any
staged decompression strategy. Within that strategy, one tries to
egress the water as quickly as possible, while maintaining the primary
objective.
Time is often seemingly paradoxical in diving. Time at depth isn't
the problem; the absence of sufficient time spent for an
appropriate, applicable staged decompression is. Time is a luxury
underwater. We unfortunately, have a finite supply of gas; thermal
considerations over time, etc., so we can't afford a bounty of time to
decompress in the water. Time is therefore, the primary focus, of a
sound decompression strategy. Minimize the decompression requirements,
whilst affording an asymptomatic egress -- win, win.
--
Randy F. Milak
Windsor, Ontario
~Rig for silent running. Aye sir, All ahead lurk...~
(1) Neuman TS. Pulmonary Disorders in Diving. Chapter 20 in: Bove AA,
Jeff
<l...@umich.edu> wrote:
>
>Popeye <buzcu...@aol.comMJBSUX> wrote in message
>news:20001106085520...@ng-ft1.aol.com...
>The diving industry often ignores "stuff" on the books enforced by EPA, OSHA
>and the FDA. It makes our industry vulnerable! (One of my "nightmares" is
>that the son or daughter of senator Bouregaurd T. Bodacious takes a quick
>weekend course and is injured. The senator, as a matter of family pride, (ie
>revenge), calls in a few favors and the EPA, OSHA and FDA start visiting the
>dive shops to enforce existing laws. This good possibly shut down our
>sport!)
>
>But.
>
>the "legality" of O2 has been discussed ad nauseum here ...mostly by
>me.(see Deja News)
>
>Let me again say, this has nothing to do with purity of gas or the
>effectiveness of a dive shop bottled gas ..it is a matter of violating US
>law. That is NOT the same discussion as chemical purity of gas mixes!
>
>
>The law is very simple.
>
>O2 is legally defined as a drug.
>
>ALL drugs for human consumption in the US MUST be sold and administered
>according to FDA standards.
>This includes that the substance be USP grade (the USP is the "book" of
>standards ...the definitions of acceptable levels of purity and the assays
>needed to insure purity for human consumption)
I wonder how the law relates to the filling of aircraft bottles, we
run about 2000 cf of O2 a week for our fleet. I'll do some checking
"behind the scenes" with my local PMI. I'll report back when I get his
opinion.
Jeff
Mike Gray
>
>
> Great, keep it up. Everyone enjoys your articles (whether they agree or
> not is another matter <g>).
Harris does a great job of assembling bibliographies, but his
understanding of FDA controls and the meaning of "prescription" as they
relate to O2 are incorrect. Like with the recent DOT thing, a little
misunderstanding provides a lot of entertainment.
m
Randy F. Milak
>
> "Randy F. Milak" wrote:
> >
>
> >
> > Great, keep it up. Everyone enjoys your articles (whether they agree or
> > not is another matter <g>).
>
> understanding of FDA controls and the meaning of "prescription" as they
> relate to O2 are incorrect. Like with the recent DOT thing, a little
> misunderstanding provides a lot of entertainment.
Then why not clear up the misunderstandings for us, and save the
ridicule for the Black et al's of the group? Hmmmm?
Ross Bagley
Mike Gray <omx...@worldnet.att.net> wrote:
[...snip...]
>Harris does a great job of assembling bibliographies, but his
>understanding of FDA controls and the meaning of "prescription" as they
>relate to O2 are incorrect. Like with the recent DOT thing, a little
>misunderstanding provides a lot of entertainment.
So are you going to actually tell us the actual facts here or just
slam the most helpful person on this newsgroup?
Also, though I know it doesn't bother you any, I'm changing my public
statements about you from, "Mike knows lots more than me." to "Mike
may know a few facts, but he's a complete ass about what he knows and
I wouldn't cross the road to piss on him if he was on fire."
Regards,
Ross
-- Ross Bagley & Associates http://rossbagley.com/rba
"We don't just write software, we help you write software better!"
Jeff
curious.
Jeff
On Mon, 6 Nov 2000 15:01:58 -0500, "Larry \"Harris\" Taylor, Ph.D."
<l...@umich.edu> wrote:
>Oxygen used for aircraft cylinders are specifically exempt from
>prescription requirements.
>
>The gas, if used by humans, used MUST be USP and the preferred purity is
>called " aviator's grade" because it has an extremely low dewpoint.
>
>
>This stuff is all spelled out in CGA publications on O2.
>
>
>"Harris"
>Larry "Harris" Taylor, Ph.D.
>Scuba Instructor, U of MI
>
Jeff
BTW how much do you charge for Dan basic O2?
Jeff
On Mon, 6 Nov 2000 15:35:33 -0500, "Larry \"Harris\" Taylor, Ph.D."
<l...@umich.edu> wrote:
>
>Jeff <jta...@dellepro.filter.com> wrote in message
>news:l15e0tca5tmkpr4l7...@4ax.com...
>> Who issued the exemption?
>> curious.
>> Jeff
>
>
>The FDA
Steven B. Harris
"Larry \"Harris\" Taylor, Ph.D." <l...@umich.edu> wrote:
>USP standards refer to those purity criteria needed to satisfy "fit for
>sale" to humans.All drugs sold in the US must have such criteria as a
>condition for sale. Other countries have similar mechanisms.
>
>A drug . like O2, either meets USP requirements or it does not. If it
does
>NOT, then, in the US, it is illegal to sell to humans. That, as far as
I
>know is NOT a negotiable item. Sale of non-USP drugs for human
consumption
>in the US, again, as I understand it, is an illegal act.
>
>A prescription is an order from a physician for a pharmacist to
>dispense a USP substance
Let me tweek this answer a bit, so long as we're on the subject. First
of all, there are all kinds of products, like herbals and supplments,
which are exempt from USP standards when offered for sale. Certainly USP
supplements (which have passed disintigration and purity tests and so
on), and even a few USP-standardized herbals exist, but you don't go to
jail if you sell non-USP kind.
Drugs (as defined by law) are another matter. From the over the counter
cold remedy to the pills you get by prescription, they must be USP in
order for the company to legally OFFER THEM FOR HUMAN USE. This includes
100% oxygen for scuba. However, this does not mean that humans cannot
use non-USP substances legally under any circumstances. It simply means
the company cannot tell them as intended for this purpose, and any use
by the consummer of a substance classed as a drug, must be on doctor's
orders.
That is why a lot of chemical companies sell a lot of fine chemicals
with the NOT INTENDED FOR HUMAN USE labels all over them. If you buy a
bottle of acetylsalicylic acid from SIGMA, that's the kind of thing it
will say on the label. It does not mean I as a physician cannot buy it
from SIGMA and give it to you, if we both feel there's no alternative.
It wouldn't make SIGMA happy to see this done, but they are covered as
far as liabilily and legality.
And so am I as a physician, so far as the narrow matter of legality, so
long as nothing goes wrong <g>. Doctors are given wide legal authority
to prescribe anything for patients, so long as the patient resides in
the state where the physician holds his/her license. So I can buy such a
chemical and dispense it to my personal patients. So long as the
substances are not controlled ones (ie, narcotics and a raft of
specifically controlled mind altering chemicals) the purity issues and
the risks are between physician and patient. This goes back to the good
old days (50 years ago) when doctors rolled and prescribed their own
foxglove leaf, and so on. I wouldn't break any laws if I prescribed eye
of newt and toe of frog, wool of bat and and tongue of dog, etc, etc.
(Witch's mummy, maw and gulf of the raven'd salt sea shark/ Root of
hemlock, digged in the dark..).
However, aside from apriori legal PROscriptions, all of this comes under
tort law, and also state malpractice laws, which are vague, and which
set the controlling standards as the "standards of practice of my peers"
(which probably don't include root of hemlock digg'd in the dark), and
leave me with burden of proof if anything at all goes wrong. So I'm
exposed there to de-licensure and getting sucessfully sued. That's
pretty much enough to put the kabosh on anything too creative, except
under very unsual circumstances.
What physicians do depends on how badly they are motivated, and what the
risks are. Once upon a time, for a close friend who had an inoperable
brain tumor, I had a radiation sensitizer drug which was in human
clinical trials, but completely unavailable, custom synthesized by some
people at a university chem dept, after which I shot up animals with it
at my lab, then took it myself, then gave it to my patient. No law was
broken, but my butt would have hanging been out in the wind had anything
gone wrong, and of course this is not anything a physician dares do for
his standard patients. My friend did fantastically and remains well now
that the drug course has long been finished, but the whole process was
scary as hell, and I wouldn't want to have to repeat it. If you have't
taken a capsule full of white etherized goo that came out of somebody's
chem lab, you haven't lived. It's not unlike skydiving.
SBH
Rich Lesperance
Randy F. Milak <mi...@divemed.zzn.com> wrote
> With respect to bubble growth, the following was described:
>
> "The initial movement of O2 into the bubble is faster than the movement
> out of N2. This causes the bubble to grow, until sufficient N2 is
> released. This presents as a transient worsening of the condition. Any
> casualty should be warned in advance about this, and reassured that it
> is normal."
I thought symptomology was still poorly correlated with bubble size or
presence? Am I incorrect?
> With respect to high PO2s increasing oxygen , the following was
> described:
<snipped>
This certainly agrees with both common sense, and what has been previously
described. While I understand the rationale behind the opposing argument
(high pO2 induced vasoconstriction), the solubility of oxygen in plasma
rises so sharply (cf "life without blood experiment" with the pig) that I'm
surprised _any_ investigators felt otherwise
Rich L
Rich Lesperance
Steven B. Harris <sbha...@ix.netcom.com@ix.netcom.com>
> Well, no. There's not a lot of evidence for that, and in the brain and
> CNS, there's some evidence against. People have tried resuscitating
> animals on higher ppO2s, and if anything the outcomes are worse on
> reperfusion.
Can you cite any studies for this? It runs rather contrary to all the
hyperbaric physiology stuff I've seen...
Rich L
Rich Lesperance
Larry "Harris" Taylor, Ph.D. <l...@umich.edu> wrote
>
>
> What do I fail to understand?
>
I don't know, but I am waiting with great interest to see Mike Gray try and
point it out....
Rich L
Rich Lesperance
Steven B. Harris <sbha...@ix.netcom.com@ix.netcom.com> wrote
>
> Not at all. Your average dive shop which mixes nitrox does it with
> prefilled large cylinders of medical grade 80/20.
What?
Where?
I live in Florida, and have patronized dive shops all over the world (well,
OK, on three continents, but you get my drift) and I have NEVER seen that.
The _only_ two ways I have ever seen nitrox made was either with a membrane,
or using bottles of 100% to do PP filling.
Where is this dive shop that has pre-banked 80/20?
Rich L
Rich Lesperance
Randy F. Milak <mi...@divemed.zzn.com> wrote
>
> Great, keep it up. Everyone enjoys your articles (whether they agree or
> not is another matter <g>).
I second that sentiment!
> Time is often seemingly paradoxical in diving. Time at depth isn't
> the problem; the absence of sufficient time spent for an
> appropriate, applicable staged decompression is. Time is a luxury
> underwater. We unfortunately, have a finite supply of gas; thermal
> considerations over time, etc., so we can't afford a bounty of time to
> decompress in the water. Time is therefore, the primary focus, of a
> sound decompression strategy. Minimize the decompression requirements,
> whilst affording an asymptomatic egress -- win, win.
Well put.
> Several strategies are
> found in the study of gas kinetics itself.
>
> Oxygen provides for an ideal offgassing gradient of high to low
> inert gas partial pressures. The higher the PO2, the more efficient the
> offgassing
Yes, and please see my comments after your next point.
> Its been suggested that a diver is "deliberately adding nitrogen to
> a gas designed to assist you in offgassing nitrogen?" Perhaps implying
> that the diver is still ongassing the N2. The gas loading derived from
> a PN2 0.18 is insignificant and nearly theoretically impossible
It was me who suggested that. I did not suggest that you were on-gassing
nitrogen. Perhaps my statement was not as succinct as it could have been.
With the election tomorrow, maybe we're all a little 'sound-bite' crazy <g>,
and I went for cute over substantive.
As you pointed out in the previous paragraph, the higher the PO2, the more
efficient the off-gassing. Not only is the PO2 higher on 100% at 20 feet, as
compared to 80/20 at 30 feet, but the added nitrogen causes problems, even
though there is no _net_ ongassing.
Let me pick my words carefully - since bubble reduction is a diffusion
function (a significant part of which is the replacement of the N2 fraction
with O2), using _any_ inspired N2 will slow down the rate at which that
diffusion occurs (because you are diffusing into a tissue [plasma] that
already _has_ some nitrogen), and therefore bubble reduction is slowed.
I don't know enough about kinetics to express it using the proper
mathematical notation, but if you increase the inspired nitrogen, you will
be slowing your off-gassing, even if there is _no_ net on-gassing (and I
agree with you, it is very unlikely for net on-gassing to happen)
Rich L
mjbl...@my-deja.com
you to sweep in that hyperbaric lab of yours, boy?
80/20 vs. 100... Gimme a break. Better yet, Harris, post this on
techdiver, and watch the pitbulls jump all over you for even mentioning
80/20. And the best part is, you are right, 80/20 is a good mix. And
my favorite color is blue, and Toyota makes a good car, etc., etc.
MJB
In article <3A06981B...@divemed.zzn.com>,
Sent via Deja.com http://www.deja.com/
Before you buy.
Mike Gray
> >
> > Harris does a great job of assembling bibliographies, but his
> > understanding of FDA controls and the meaning of "prescription" as they
> > relate to O2 are incorrect. Like with the recent DOT thing, a little
> > misunderstanding provides a lot of entertainment.
>
> ridicule for the Black et al's of the group? Hmmmm?
Ridicule only for the deserving.
The O2 stuff was beaten to death about six month ago, but, for you, a
recap:
O2, like sterile water and lithium, is controlled by the FDA only when
used for medical purposes. Scuba, yuppy refreshment, and battery
production are not considered medical purposes.
"Prescription" means dispensed for use under the supervision of a
physician. Aspirin or O2 dispensed for use under the supervision of a
physician is prescription aspirin or O2. Certain drugs may be dispensed
ONLY with a prescription, and that list varies slightly from state to
state. In Florida, O2, aspirin, and insulin can be each be bought
without a prescription. Few insurance companies, however, will reimburse
for them unless they are used under the supervision of a physician, i.e.
prescription. Get yer doctor to prescribe the O2, and you might get
reimbursed. But then it is also subject to FDA regs. FDA regs do cover,
btw, the less than 100% O2 which is delivered by medical oxygen
concentrators. If you use the precise same technology to produce nitrox
for scuba, the FDA regs do not apply.
Any commercial gas supply house in Florida will sell medical or aviation
grade O2 to buyers they know. Because of the handling risks, they might
be reticent to sell it (or acetylene) to some yahoo walking in off the
street.
Medical supply houses often will not sell anything except for third
party reimbursement, which means prescription. Liability may be a
concern, but the big issue is price: the O2 that Medicare buys is too
expensive for diving, and a Medicare provider cnnot sell it to you for
less than they sell it to Medicare.
So, go to a reputable gas supply house, show them yer blender
credentials, and they will sell you all the O2 you want, cheap. Or just
buy a molecular sieve and make yer own - it's all over yer back yard for
free. Well, here in SoFla it is.
m
Mike Gray
>
> Randy F. Milak <mi...@divemed.zzn.com> wrote in message
> news:3A071A24...@divemed.zzn.com...
> > Mike Gray wrote:
> > >
> > > "Randy F. Milak" wrote:
> > > >
> > >
> > > >
> or
> > > > not is another matter <g>).
> > >
> > > understanding of FDA controls and the meaning of "prescription" as they
> > > relate to O2 are incorrect. Like with the recent DOT thing, a little
> > > misunderstanding provides a lot of entertainment.
> >
>
> sale" to humans.All drugs sold in the US must have such criteria as a
> condition for sale. Other countries have similar mechanisms.
>
> A drug . like O2, either meets USP requirements or it does not. If it does
> NOT, then, in the US, it is illegal to sell to humans. That, as far as I
> know is NOT a negotiable item. Sale of non-USP drugs for human consumption
> in the US, again, as I understand it, is an illegal act.
>
> A prescription is an order from a physician for a pharmacist to dispense a
> USP substance
>
Pretty much all of the above.
See my response to Milak.
m
Mike Gray
>
>
> The difference is THE LABEL ... the USP on the label is your guarantee, as a
> consumer, that the drug being purchased has a documented history that
> certifies it is acceptable to the medical/legal community for use in
> humans.THE USP label on drugs for human use is part of a long standing
> system devised by the medical/legal community to insure drug quality.It is a
> LEGAL process.
No. It is a regulatory process. It is a definition of jurisdiction, no
more.
Mike Gray
>
> Also, though I know it doesn't bother you any, I'm changing my public
> statements about you from, "Mike knows lots more than me." to "Mike
> may know a few facts, but he's a complete ass about what he knows and
> I wouldn't cross the road to piss on him if he was on fire."
Thank you. Thank you very much.
You are prohibited from reading my response to Milak.
m
Popeye
>used for medical purposes. Scuba, yuppy refreshment, and battery
>production are not considered medical purposes.
>
Cool, thanks Mike! Excellent post and thread.
Popeye
5 Bucks on Team 3
Mike Gray
>
> So are you going to actually tell us the actual facts here or just
> slam the most helpful person on this newsgroup?
I didn't "slam" Harris, I said he is wrong. He is.
I would expect you to get yer panties in a wad by pointing out an error
by a hero.
But the fact is, this subject was exhausted just a few months ago and
the dead never got it. Learn to pay attention.
m
Mike Gray
I never heard of 80% cylinders, but using a membrane or sieve might
allow banking a resulting 80%.
m
mjbl...@my-deja.com
"Larry \"Harris\" Taylor" <dive...@earthlink.net> wrote:
> The retina of the eye and the inner ear are extremely sensitive to
> high concentrations of O2 ... SOME people will have visual
> disturbances and ringing in the ears following 100% O2 exposures.
> (This can persist for days following diving) If this is the case,
> the O2 concentration needs to be lowered a bit
Are you confusing retinal pathology with lens changes (hyperoxic
myopia) which can last for days. Clinically I have seen neither,
but would not expect retinal changes from hyperoxic exposures to
last for days. Reference?
Agree with everything else you've said so far: 100% is best on the
surface, 80/20 is appropriate for deco, FDA requirements, USP labeling,
legal ramifications. MJB
Steven B. Harris
"Rich Lesperance" <ri...@ufl.edu> wrote:
>
>Steven B. Harris <sbha...@ix.netcom.com@ix.netcom.com> wrote
>
>>
>> Not at all. Your average dive shop which mixes nitrox does it with
>> prefilled large cylinders of medical grade 80/20.
>
>What?
>
>Where?
>
>I live in Florida, and have patronized dive shops all over the world
(well,
>OK, on three continents, but you get my drift) and I have NEVER seen
that.
>The _only_ two ways I have ever seen nitrox made was either with a
membrane,
>or using bottles of 100% to do PP filling.
>
>Where is this dive shop that has pre-banked 80/20?
>
>Rich L
>
Scuba Schools of America in Montclair, California, for one place. They
are one of the primo nitrox places in California.
Popeye
>
>
>Scuba Schools of America in Montclair, California, for one place. They
>are one of the primo nitrox places in California.
>
>
"FIRE IN THE HOLE!"
Bob Crownfield
>
> WHOOOPPPEEEEE!!!! Doctor Milak is back! Isn't there a floor for
> you to sweep in that hyperbaric lab of yours, boy?
>
> 80/20 vs. 100... Gimme a break. Better yet, Harris, post this on
> techdiver, and watch the pitbulls jump all over you for even mentioning
> 80/20. And the best part is, you are right, 80/20 is a good mix. And
> my favorite color is blue, and Toyota makes a good car, etc., etc.
>
> MJB
but then you have so little choice. I feel sorry for you.
/\ /\
( \\ // )
\ \\ // /
\_\\||||//_/
"" \/ _ _ \
|| \/|(.)(.)| wrong
|| \/ | | bull shit
\\ __________________\/ \ / hot air
\\ / // |____| poor judgement.
. \/ || / \ bad taste.
pop . . | \| \ 0 0 / presumptousness.
fizz . \ ) V / \\__/ - . ignorance.
splot \ / ( / inconsideration.
fizz \ /_________| |_/ always wrong.
putt / /\ / | || /\___
pip / / / / \ || @@@@@@@@@@@ O \.
splop | | | | ____| || @@@@@@@@@@@@@@@___\/
| | | | /_|____|| @@@@@@@@@@@@@@@@ your rectum
|_| |_| |_| @ @@@@@@@@@@@@ is smarter
\_\ \_\ \_\ @@@@@@@@@@@ than your mouth.
|| || you silly ass!
--
Bob Crownfield, Crown...@Home.com
Photography, Flying, Delphi Rad Addict
Now diving the Pacific in the LA Area.
"Protect freedoms before they become extinct."
Jammer Six
<sbha...@ix.netcom.com@ix.netcom.com> wrote:
>€ Scuba Schools of America in Montclair, California, for one place. They
>€ are one of the primo nitrox places in California.
Well, no.
If they bank 80/20, (and this is giving you a serious benefit,
doubt-wise), that would make them a stroke shop, and not a primo
anything.
Hey, *I* have an idea!
Why don't you tell us why 80/20 is the way to go, Steve?
With an M.D. after your name, and all, you should know quite a bit
about oxygen.
How about it? What should I use 80/20 for, and why?
I got another $100 dollar bill, here, Steve, and you owe me $100, so
what say we double up?
Same terms, wee one. I'll accept silence as concession.
Here we go, for the third time this week, buddy!
The score right now is DIR 2, You, zero.
Put up, or shut up, yet again.
--
"C'mon, you sons of bitches, you want to live forever?"
-Sergeant Major Dan Daly
Popeye
>>€ are one of the primo nitrox places in California.
>
>Well, no.
>
>If they bank 80/20, (and this is giving you a serious benefit,
>doubt-wise), that would make them a stroke shop, and not a primo
>anything.
>
Jammer,
SSA, didn't we burn them at the stake? Home of the 80# custom BC that you
have to buy or go elsewhere to get certified? Does the name Rusty Berry ring a
bell?
I thought we tarred and feathered that guy. It was a "primo" job.
I Deja'd the legendary thread "My OW1 Experience (kinda long)":
About a month ago I posted a question to this newsgroup regarding B.C.'s with
#80 of lift, and the fact that the instructor at the store I was taking my open
water CERT required that any B.C. we had was capable of this amount of lift. I
explained that I had bought a Seaquest Black Diamond B.C., and was told by the
instructor that I would not be able to use it during his class, due to that
fact that it did'nt have enough lift.
I received about 45 responses all of them telling me that the guy was crazy,
and to find somewhere else to get my CERT from.
Well, this is the final chapter to my story of my experience at Scuba Schools
of America in Montclair, Ca.
You should check it out...
OldSalt
<mi...@divemed.zzn.com> wrote and since I have Supernews, it's amazing
that I could even see it:
> With respect to bubble growth, the following was described:
<snipping alllll kinds of heavy duty stuff that Randy is well-known
for and that I don't understand...>
Nice to see you back Mr Milak. Stick around a while this time. :)
Steven B. Harris
Jammer Six <jam...@oz.net> wrote:
>>
>Hey, *I* have an idea!
>
>Why don't you tell us why 80/20 is the way to go, Steve?
>
>With an M.D. after your name, and all, you should know quite a bit
>about oxygen.
>
>How about it? What should I use 80/20 for, and why?
COMMENT
You must not have been following this thread, since I've gone
over most of this, and so has Harris.
The 80/20 mix is useful mainly because of the utility of the 20
ft (6m) deco stop. Oxygen 100% at that depth is at 1.61 bar in
salt water, which is too toxic to plan for. Hamilton, who is
probably the leading expert on deco, says that 1.6 bar O2 on deco
is "a limit, NOT a target." Though Hamilton is supposed to be
Irvine's deco guru, the two seem to have a failure to communicate
on this point, because Irvine's writings make it clear that he
does plan for 1.6 bar. Moreover, he shows a great deal of
contempt and rigidity for people who might (from wave action or
whatever) be a foot or two up or down. As well he might, since
this is the very edge of the cliff, at a place where even 0.1 bar
makes a huge difference in safety factor (the target for short
deco times should be more like 1.5 bar for safety). As noted, 1.6
is the cliff edge, and Irvine deliberately plans to be at that
edge, and for no particularly good reason.
Consider: we have the WKPP guys, who are so paranoid about their
BC QR's giving way, planning for an oxygen deco at 1.6 bar. ROFL.
You lose how many minutes-- five?-- on deco obligation from using
80/20 at 1.3 bar ppO2 from 6 m on up, but your payoff is a hugely
reduced chance of doing the funky chicken, spitting out your reg,
and drowning in a silly 20 feet of water. Maybe if Irvine
planned to breathe some high O2 mix, or even 100% at the surface,
he wouldn't be in such a hurry to deco at 20. He's diving
springs, and certainly somebody could bring him an E cylinder
when he gets up, you think? Anyway, I don't know what his
problems are, but they don't have to be mine. And I don't care
what he's gotten away with in the past-- his own arguments
regarding risks are enough to cite on that. His time is probably
coming.
uglyman
>
> With an M.D. after your name, and all, you should know quite a bit
> about oxygen.
>
>
> --
> "C'mon, you sons of bitches, you want to live forever?"
> -Sergeant Major Dan Daly
--
Perhaps he missed out the A????? :)
Mike Gray
>
>
> So, playing plantiff here, please explain to the jury how using a drug
> called oxygen to remove excess nitrogen from the body to prevent a disease
> called decompression sickness is exempt from Federal control of drugs.used
> in the prevention or treatment of diseases?
Happy to, counsel. The question is jurisdiction. The FDA has
jurisdiction over anything that makes claims for medical treatment. If I
say drink this water and you'll be cured, it is FDA water. If O2 or, for
that matter, plain old air, is used for treatment (wound care, DCI) it
falls under FDA jurisdiction and the FDA may regulate or give an
exemption.
> Or, if the cylinder filled was a 100% O2 DAN emergency use only cylinder,
> explain to the jury why the first aid procedure (administration of the drug
> oxygen) for the relief of signs and symptoms of the disease called
> decompression illness is exempt from Federal regulation of drugs?
A cylinder filled for treatment is under FDA jurisdiction, and they have
the choice of writing and enforcing rules or exempting. Whether exempt
or not, DAN O2 administration is regulated by the FDA while a 100% O2
deco is not. The former is intended for treatment, the latter is not.
That is where all the confusion comes in: it is not the material (O2)
that is in question, it is how the material is intended to be used.
If you sell lithium for batteries or grease, the FDA has no
jurisdiction. As soon as you sell the exact same lithium for relief of
mental disorders, the FDA has jurisdiction.
> and, if using a non-USP gas, explain to the jury why you are using a drug
> not certified for human use in your first aid or prevention of disease
> protocols?
USP stands for United States Pharmacopaeia. The USP is a listing of
standards for materials used in treatment protocols. The USP lists
things like sterile water which is, well, sterile water, boric acid
identical to the stuff you buy at home depot, lithium identical to the
stuff you put in yer door locks, and Oxygen just like the stuff in yer
back yard. "USP" means that the material meets the standards listed in
the USP. It would be nice to know that my deco O2 is USP and it would be
just as nice to know that my welding O2 is USP, but neither is
necessary. However by law, O2, sterile water, and lithium used for
medical treatment MUST be USP. Scuba diving is not generally considered
to be a medical treatment as defined by the FDA despite the fact it's
the only thing between me and serial murder. The FDA therefore does not
care if your tank is filled with O2, sterile water, or dirt.
>
> Then, ask yourself if you are willing to bet your home, life savings and
> investments and all future livlihood on your ability to convince the jury
> that Federal drug regulations to NOT apply to the diving industry.
FDA jurisdiction extends to treatment of dive related injury. It does
not extend to the breathing medium in yer tanks. They might like to have
that jurisdiction, but we haven't given it to them yet.
> Finally, he says, rhetorically (g)
>
> Let's really get absurd here .... are you suggesting that if I use valium,
> scopalamine or penicillin strictly as a seasoning to prevent my ice cream
> from tasting poorly (clearly, a non-medical application) that I am exempt
> from Federal regulation in the purchase or sale of said seasoning?
Actually, most seasonings are regulated by the FDA, as are the food
colorings used to make them pretty.
Let's say, rhetorically, that it is discovered that slathering
penicillin on yer scuba tank prevents corrosion. Then yes, I can make
and sell penicillin for the slathering of scuba tanks completely outside
FDA jurisdiction, and you can slather it on yer own tanks to yer heart's
content. No different than the unregulated silicone you put on yer
O-rings, which almost certainly meets USP standards, is listed in the
USP, and is regulated by the FDA if you use it to lube an endoscope or
augment yer titties.
In fact, USP silicone and the goo ya put on yer Orings is the exact same
stuff, came from the same vat. The USP stuff was then tested to confirm
that it meets USP standards and the price doubled. It's OK to use USP
silicone on yer O-rings, and doing so does not put yer Orings under FDA
jurisdiction.
regards
m
mjbl...@my-deja.com
your honor, that state laws regarding handling of oxygen may have
priority over federal regulations. Whereas Mike Gray can legally
obtain oxygen without a prescription in Florida, Harris Taylor
cannot in Michigan. MJB
In article <WbNN5.27517$Pw6.2...@newsread1.prod.itd.earthlink.net>,
"Larry \"Harris\" Taylor" <dive...@earthlink.net> wrote:
>
> "Mike Gray" <omx...@worldnet.att.net> wrote in message
> news:3A07537C...@worldnet.att.net...
> > "Randy F. Milak" wrote:
> > > >
> > > > Harris does a great job of assembling bibliographies, but his
> > > > understanding of FDA controls and the meaning of "prescription"
as
> they
> > > > relate to O2 are incorrect. Like with the recent DOT thing, a
little
> > > > misunderstanding provides a lot of entertainment.
> > >
> > > Then why not clear up the misunderstandings for us, and save
the
> > > ridicule for the Black et al's of the group? Hmmmm?
> >
> > Ridicule only for the deserving.
> >
> > The O2 stuff was beaten to death about six month ago, but, for you,
a
> > recap:
> >
> > O2, like sterile water and lithium, is controlled by the FDA only
when
> > used for medical purposes. Scuba, yuppy refreshment, and battery
> > production are not considered medical purposes.
>
> So, playing plantiff here, please explain to the jury how using a drug
> called oxygen to remove excess nitrogen from the body to prevent a
disease
> called decompression sickness is exempt from Federal control of
drugs.used
> in the prevention or treatment of diseases?
>
> Or, if the cylinder filled was a 100% O2 DAN emergency use only
cylinder,
> explain to the jury why the first aid procedure (administration of
the drug
> oxygen) for the relief of signs and symptoms of the disease called
> decompression illness is exempt from Federal regulation of drugs?
>
> and, if using a non-USP gas, explain to the jury why you are using a
drug
> not certified for human use in your first aid or prevention of disease
> protocols?
>
> Then, ask yourself if you are willing to bet your home, life savings
and
> investments and all future livlihood on your ability to convince the
jury
> that Federal drug regulations to NOT apply to the diving industry.
>
> Finally, he says, rhetorically (g)
>
> Let's really get absurd here .... are you suggesting that if I use
valium,
> scopalamine or penicillin strictly as a seasoning to prevent my ice
cream
> from tasting poorly (clearly, a non-medical application) that I am
exempt
> from Federal regulation in the purchase or sale of said seasoning?
>
> --
> "Harris"
> Larry "Harris" Taylor, Ph.D.
> Scuba Instructor, U of MI
Mike Gray
>
> But, for me, as a diver and instructor, I want my gas USP
I do, too, I think. If the aviation O2 standards are higher than USP,
then I'll take the av standards. (Now I gotta go actually look up the
standards)
> and I, personally, would not want to stand before a jury outside of FDA
> protocols.
If you are administering it for treatment, yer right. And I will admit
there's a grey area in filling tanks that the FDA might like to have
(power hungry bastards!) or might not want at all (why take on the
hassle?).
The REAL problem is not actually a question of O2, though. The REAL
question is, "Do you know what the shop is pumping into yer tanks for
hyperbaric inspiration?" The real problem is whether your
air/O2/He/whatever is fit to breathe at high PP, and there's very little
control over that. The shop accepts whatever comes in the big green and
brown tanks without purity testing. They may or may not check their
filters this millenium. If the shop has greenies and brownies labeled
"USP", that does indeed make me feel a bit safer sucking their trimix at
depth than the shop with the tanks that say "Save money - return yer
hazardous waste in this cylinder".
On the one hand, I do wish there were strong and well enforced standards
for what's in my tanks. On the other hand, I've dealt with the FDA and
other gov't standard setters and I don't want any of them telling me
what and what not I can put in my tanks.
That's the REAL question, and I don't have a clue.
regards
m
Michael J. Blitch
<l...@umich.edu> wrote:
>
>Mike Gray <omx...@worldnet.att.net> wrote in message
>news:3A08103E...@worldnet.att.net...
>> Larry \"Harris\" Taylor wrote:
>> >
>
><<<<:lots snipped>>>
>
>very nice explanation ... logical and well put. Thanks!
>
>But, for me, as a diver and instructor, I want my gas USP
>
>and I, personally, would not want to stand before a jury outside of FDA
>protocols.
>
>But, as everyone here realizes by now, I always look at the "worst case"
>scenario.
What about for personal mixing? Does one have to get a prescription
for human consumption in order to get helium? Anything can be
indefensible or attacked in court.
"So, you knowingly filled my client's tank with Grade E air instead of
the more pure Grade J? Did you not think that the small cost involved
was not worth the extra safety? What other cost cutting measures did
you take that contributed to the death of my client?"
--
You know you're addicted to the Internet when...
You realize there is not a sound in the house and you have no idea where your children are.
Michael J. Blitch
<l...@umich.edu> wrote:
>
>Mike Gray <omx...@worldnet.att.net> wrote in message
>news:3A08103E...@worldnet.att.net...
>> Larry \"Harris\" Taylor wrote:
>> >
>
><<<<:lots snipped>>>
>
>very nice explanation ... logical and well put. Thanks!
>
>But, for me, as a diver and instructor, I want my gas USP
>
>and I, personally, would not want to stand before a jury outside of FDA
>protocols.
>
>But, as everyone here realizes by now, I always look at the "worst case"
>scenario.
Before the blanket OSHA variance, Dr. Taylor, did you ever teach a
dive class while using nitrox? Even though this could have been
technically against regulations, did you ever use it in a dive class?
I am sure that there are dozens of stupid, outdate, and illogical
regulations, rules, and policies that relate to diving. Ask 10
different people in the government what the rule interpretation may
be, and you'll likely get at least 11 opinions. While I would not ever
provide nitrox or trimix fills for any of my students, I don't have a
problem in helping friends get cheaper access to nitrox. I will be
bringing my own O2 cylinder to WPB with me for fills. It is cheaper
for me and I can always get what I want, I know the source, and I
don't have to worry about any 100% mark up fee. I use aviator's grade
oxygen for my fills. My cost is about $22 for a bottle and one can get
at least 15 - 20 32% fills on that single bottle. Using a cascade
system, it is more efficient, although a booster pump is on my
Christmas wish list, like it will ever happen. <G>
--
Things I'd Do If I Ever Became An Evil Overlord:
82: I will not shoot at any of my enemies if they are standing in front of the crucial support beam to a heavy, dangerous, unbalanced structure.
Michael J. Blitch
<l...@umich.edu> wrote:
> >Even though this could have been
>> technically against regulations, did you ever use it in a dive class?
>> I am sure that there are dozens of stupid, outdate, and illogical
>> regulations, rules, and policies that relate to diving.
>
>EMPHASIS on COULD, but I believe I was in a stronger position to defend a 14
>hours of lecture, 3 dives with on-site analysis of mix type class than
>someone selling non-USP O2 for refill on a DAN cylinder ... obviously, a
>matter of opinion! (g)
I agree. I was just curious. I am quite sure you could defend yourself
quite well, especially when you are so involved in these aspects. You
have more references in you library than any lawyer could come up with
no matter how long they spent in the discovery phase.
>Absolutely, but just 'cause a law is stupid or unpopular does NOT mean it
>will NOT be enforced in court.
Agreed.
>But, in terms of safety and standards I stand a bit more conservative than
>Barry Goldwater (shows my age!)
Who? (shows my age) <g>
Jammer Six
<sbha...@ix.netcom.com@ix.netcom.com> wrote:
>€ You must not have been following this thread, since I've gone
>€ over most of this, and so has Harris.
And you still haven't got it right, have you?
Didn't you listen?
They broke it down so simply that even a simple guy like me understands
it, but not you...
Ross Bagley
>> called oxygen to remove excess nitrogen from the body to prevent a disease
>> called decompression sickness is exempt from Federal control of drugs.used
>> in the prevention or treatment of diseases?
>
[...snip...]
Thank you very much, Mike. Again, I'm fairly certain it doesn't
matter much to you, but my humble opinion is back to, "Mike knows lots
more than me."
Regards,
Ross
-- Ross Bagley & Associates http://rossbagley.com/rba
"We don't just write software, we help you write software better!"
Randy F. Milak
> function (a significant part of which is the replacement of the N2 fraction
> with O2), using _any_ inspired N2 will slow down the rate at which that
> diffusion occurs (because you are diffusing into a tissue [plasma] that
> already _has_ some nitrogen), and therefore bubble reduction is slowed.
Well chosen, and it's very true. Common ground lies in the fact
that 100% oxygen used for staged decompression is the most effective gas
to eliminate any inert gas tissue load. I would concede, that,
providing oxygen toxicity limits are well within an acceptable risk
level to satisfy ones own risk management criteria, then, one should
always choose the best gas (as defined by expedience and efficiency for
offgassing) for all stages of the decompression regime.
The EAN 80 vs 100% debates always seem to ramble on about the same
old same old; one side claiming oxygen toxicity the other claiming that
its not as effective at offgassing etc. etc. to ad nausea. What I
believe, is that the diver needs to make a well defined decompression
strategy, based on a vigilance for life preservation, injury avoidance,
and base it on solid risk analysis. Simple fact is, is that neither gas
is the "BEST" gas to use under EVERY given staged decompression criteria
simply because expedience of decompression, although at the top of the
list, is not the only criteria. Example - single, none repetitive,
mixed gas dive with 30% or better helium content, less than 220 fsw,
less than 60 minute bottom time, double gas switch deco with possible
full face mask availability, then no brainer, 100% without a doubt.
Conduct that same dive twice a day for the next six days utilizing 100%
oxygen, then perhaps the diver should take a second look. I could take
either side of the 100% vs EAN 80 debate and form a sound argument.
What I wouldn't do, is close off my options.
Risk management is not about one specific criteria. By the same
token, risk management is not universal either. To a large extent, risk
and safety are a matter of opinion and an individual's viewpoint. I
suppose that's why we debate. For the most part, I can not actually
take either side of an 80/20 vs 100% debate and argue it like either of
them are the only way in the world to decompress. I could only suggest
that divers weigh the risks they are taking against the rewards. For
each diver, for each circumstance, the answers will be different. I
don't swim, breath or dive for someone else and will not be so
presumptuous as to dictate only one way, since there are several. Diver
education is key.
> I don't know enough about kinetics to express it using the proper
> mathematical notation, but if you increase the inspired nitrogen, you will
> be slowing your off-gassing, even if there is _no_ net on-gassing (and I
> agree with you, it is very unlikely for net on-gassing to happen)
Everyone discusses basic interpretations of gas kinetics in terms
of either exponential inert gas uptake and elimination, or, as
exponential inert gas uptake followed by linear elimination; such as
found in your carefully worded first paragraph. That's where one
discovers that, "you will be slowing your off gassing" using less than
100% deco gas. Not often addressed in ascent criterion discussions are
aspects of free phase bubble growth and what happens to them in
different mixed gas/EAN decompressions. Why? Probably because
supersaturation theory is much simpler to understand than bubble
mechanics. Anyways, within that theory are interesting aspects of
formed bubble stability during the decompression stages, that would add
to the 100% argument over 80/20. I only mention it, because its
something that rarely if ever, seems to get addressed (besides, it
doesn't help my 80/20 argument at the moment either <G>).
Ross Bagley
Mike Gray <omx...@worldnet.att.net> wrote:
>Ross Bagley wrote:
>>
>> So are you going to actually tell us the actual facts here or just
>> slam the most helpful person on this newsgroup?
>
>I didn't "slam" Harris, I said he is wrong. He is.
He can very well be wrong, but it's the way you say it that makes it
a "slam" or "criticism". You slammed him.
>I would expect you to get yer panties in a wad by pointing out an error
>by a hero.
Nope. I didn't get upset when you pointed out the error, I got upset
when you *just* pointed out the error without correcting it.
Now that you've gone ahead and actually discussed the issue, explaining
your argument in fairly great detail, I accept your apology :)
Steven B. Harris
Mike Gray <omx...@worldnet.att.net> wrote:
>Larry \"Harris\" Taylor wrote:
>>
>
>>
>>So, playing plantiff here, please explain to the jury how using a drug
>>called oxygen to remove excess nitrogen from the body to prevent a
>>disease called decompression sickness is exempt from Federal control
>>of drugs.used in the prevention or treatment of diseases?
>
>Happy to, counsel. The question is jurisdiction. The FDA has
>jurisdiction over anything that makes claims for medical treatment. If
>I say drink this water and you'll be cured, it is FDA water. If O2 or,
>for that matter, plain old air, is used for treatment (wound care, DCI)
>it falls under FDA jurisdiction and the FDA may regulate or give an
>exemption.
Yeeeesss.
>>Or, if the cylinder filled was a 100% O2 DAN emergency use only
>>cylinder, explain to the jury why the first aid procedure
>>(administration of the drug
>> oxygen) for the relief of signs and symptoms of the disease called
>> decompression illness is exempt from Federal regulation of drugs?
>A cylinder filled for treatment is under FDA jurisdiction, and they
>have the choice of writing and enforcing rules or exempting. Whether
>exempt or not, DAN O2 administration is regulated by the FDA
That is correct. The FDA ruled in 1996, in response to a petition by
the CGA, that they would except dispensing of O2 for treatment of DCI in
emergencies.
>while a 100% O2 deco is not. The former is intended for treatment, the
>latter is not.
No, the latter if intended for prevention, which still comes under FDA
jurisdiction.
Now, it is possible that if EAN or 100% was used without anybody
(including ANDI and the rest of the nitrox associations) making any
claim WHATSOEVER that it functioned in the role of a preventative for
DCI, then possibly the FDA would lose jurisdiction, and it would be
similar to people breathing oxygen in oxygen bars, just for the
entertainment value of it. But people do not breathe EAN for the
entertainment value, and it is not sold for the entertainment value by
the industry that pushes. Read some ANDI literature. EAN has gone far
beyond that by now. It meets FDA criteria as a drug, because it's not
air and it's not food, and it's being used for a preventive purpose,
against a very serious pathological physiological damage condition,
without a prescription. That's it. I'm sorry you don't get it.
True, the FDA hasn't enforced this. But that's only because the FDA are
doofuses, and officially, they don't even KNOW about EAN. They think
scuba cylinders are filled with compressed air, and nobody has really
told them differently, and asked for a ruling. If anybody does push the
issue (and it is bound to come sooner or latter) I have no doubt at all
what the FDA will do.
>
>That is where all the confusion comes in: it is not the material (O2)
>that is in question, it is how the material is intended to be used.
>
>If you sell lithium for batteries or grease, the FDA has no
>jurisdiction. As soon as you sell the exact same lithium for relief of
>mental disorders, the FDA has jurisdiction.
Yes, you're getting it. But also if you sell lithium to prevent
episodes of mental disorders. Now, is this becoming more clear?
>
>> and, if using a non-USP gas, explain to the jury why you are using a
>>drug not certified for human use in your first aid or prevention of
>>disease protocols?
>
>USP stands for United States Pharmacopaeia. The USP is a listing of
>standards for materials used in treatment protocols. The USP lists
>things like sterile water which is, well, sterile water, boric acid
>identical to the stuff you buy at home depot, lithium identical to the
>stuff you put in yer door locks, and Oxygen just like the stuff in yer
>back yard. "USP" means that the material meets the standards listed in
>the USP. It would be nice to know that my deco O2 is USP and it would
be
>just as nice to know that my welding O2 is USP, but neither is
>necessary. However by law, O2, sterile water, and lithium used for
>medical treatment MUST be USP. Scuba diving is not generally considered
>to be a medical treatment as defined by the FDA despite the fact it's
>the only thing between me and serial murder. The FDA therefore does not
>care if your tank is filled with O2, sterile water, or dirt.
No. The FDA hasn't really thought about what happens to their
jurisdiction if your tank isn't filled with air. That's it. Their
rulings make this clear.
>
>Let's say, rhetorically, that it is discovered that slathering
>penicillin on yer scuba tank prevents corrosion. Then yes, I can make
>and sell penicillin for the slathering of scuba tanks completely
>outside FDA jurisdiction, and you can slather it on yer own tanks to
>yer heart's content.
Sure.
> No different than the unregulated silicone you put on yer
>O-rings, which almost certainly meets USP standards, is listed in the
>USP, and is regulated by the FDA if you use it to lube an endoscope or
>augment yer titties.
Sure. Use it to augment your titties, however, and you're in trouble.
In more ways than one.
Not long ago the FDA blocked importantion of "SPORTS OXYGEN", a little
system of O2 from Japan which was supposed to boost your sports
performance if you breathed it. That was held to be a medical claim,
because it said something about what it would do beneficially to your
physiology, and made it clear this was not an entertainment issue. Had
the Japanese tried to import tanks of EAN nitrox to prevent bends with,
while doing the sport of diving, we'd be in trouble now.
The FDA is a giant that hasn't noticed the dive industry yet, because
they are too dumb. But our time is coming.
Steven B. Harris
Mike Gray <omx...@worldnet.att.net> wrote:
>"Larry \"Harris\" Taylor, Ph.D." wrote:
>>
>
>
>> But, for me, as a diver and instructor, I want my gas USP
>
>I do, too, I think. If the aviation O2 standards are higher than USP,
>then I'll take the av standards. (Now I gotta go actually look up the
>standards)
>
>> and I, personally, would not want to stand before a jury outside of
FDA
>> protocols.
>
>If you are administering it for treatment, yer right. And I will admit
>there's a grey area in filling tanks that the FDA might like to have
>(power hungry bastards!) or might not want at all (why take on the
>hassle?).
>
>The REAL problem is not actually a question of O2, though. The REAL
>question is, "Do you know what the shop is pumping into yer tanks for
>hyperbaric inspiration?" The real problem is whether your
>air/O2/He/whatever is fit to breathe at high PP, and there's very
little
>control over that. The shop accepts whatever comes in the big green and
>brown tanks without purity testing. They may or may not check their
>filters this millenium.
But they do check their gas purity by analysis every so often, if they
are an ANDI shop. That's the idea of SafeAir. Get with the program,
Mike.
>On the one hand, I do wish there were strong and well enforced
standards
>for what's in my tanks.
Well, look for the ANDI sticker on your shop. Use the Yellow Pages.
Got to the ANDI site and look for addresses. Hell, there are 50 ANDI
sites outside the country-- I'm sure there's one near where you live IN
the US.
>On the other hand, I've dealt with the FDA and
>other gov't standard setters and I don't want any of them telling me
>what and what not I can put in my tanks.
>
>That's the REAL question, and I don't have a clue.
Now you've put your finger on the problem (sweet smile inserted).
Educate yourself.
Steven B. Harris
Michael J. Blitch <mbli...@tampabay.rr.com> wrote:
>What about for personal mixing? Does one have to get a prescription
>for human consumption in order to get helium?
In theory, if the helium is for human consumption, and is intended to
treat OR PREVENT disease, rather than for the purpose of doing Chipmunk
immitations, then the answer is yes. In theory, you need a prescription.
This law has yet to be broadly enforced, but the FDA is tenacious and
nasty, and when it is enforced, you are not going to like it. The FDA
a few years ago made the entire US army get rid of most of its stocks of
frozen blood, because it didn't meet approval standards for the use it
was intended for. That's THE U.S. army-- the guys with the tanks and
nukes, remember? The FDA steamrollered right over them.
You think it's going to pause when it officially notices that that sport
dive industry has been widely using things other than compressed air,
and doing it purposes of prevention of DCS/DCI? ROFL.
OldSalt
<sbha...@ix.netcom.com@ix.netcom.com> wrote and since I have
Supernews, it's amazing that I could even see it:
From Dr Taylor:
>>If you sell lithium for batteries or grease, the FDA has no
>>jurisdiction. As soon as you sell the exact same lithium for relief of
>>mental disorders, the FDA has jurisdiction.
>Yes, you're getting it. But also if you sell lithium to prevent
>episodes of mental disorders. Now, is this becoming more clear?
Steven... perhaps using Lithium as an example isn't quite right. No
one sells or prescribes it to "prevent" the initial episode. The
patient is diagnosed with the problem and then the med is given for
treatment, yes ?
Steven B. Harris
Jammer Six <jam...@oz.net> wrote:
>In article <8u8psg$h72$1...@slb0.atl.mindspring.net>, Steven B. Harris
><sbha...@ix.netcom.com@ix.netcom.com> wrote:
>
>>€ You must not have been following this thread, since I've gone
>>€ over most of this, and so has Harris.
>
>And you still haven't got it right, have you?
>
>Didn't you listen?
>
>They broke it down so simply that even a simple guy like me understands
>it, but not you...
They told you things that are not true about the jurisdiction of the
FDA. It has jurisdition over any gas mix, including EAN nitrox, which is
sold for the prevention of a disease, like decompression illness. The
fact that this has not (yet) been enforced, means exactly nothing. The
FDA still thinks scuba cylinders are filled with air, as judged by the
lastest ruling I can find on the issue (1997).
Now-- how much of the above don't you understand? You want me to use
smaller words?
Randy F. Milak
>
> In article <k7guts4oolehf8me3...@4ax.com>,
> Michael J. Blitch <mbli...@tampabay.rr.com> wrote:
>
> >What about for personal mixing? Does one have to get a prescription
> >for human consumption in order to get helium?
>
> In theory, if the helium is for human consumption, and is intended to
> treat OR PREVENT disease, rather than for the purpose of doing Chipmunk
> immitations, then the answer is yes. In theory, you need a prescription.
Really? Then what do you call a bartender: a pharmacist with a
limited inventory?
Steven B. Harris
r...@jump.net (Ross Bagley) wrote:
>In article <3A08103E...@worldnet.att.net>,
>Mike Gray <omx...@worldnet.att.net> wrote:
>>Larry \"Harris\" Taylor wrote:
>>>
>>
>>>
>>> So, playing plantiff here, please explain to the jury how using a
drug
>>> called oxygen to remove excess nitrogen from the body to prevent a
disease
>>> called decompression sickness is exempt from Federal control of
drugs.used
>>> in the prevention or treatment of diseases?
>>
>>Happy to, counsel.
>
>[...snip...]
>
>Thank you very much, Mike. Again, I'm fairly certain it doesn't
>matter much to you, but my humble opinion is back to, "Mike knows lots
>more than me."
A fair assessment, probably. And in this case he doesn't know much. But
keep learning.
Jammer Six
<sbha...@ix.netcom.com@ix.netcom.com> wrote:
>€ Now-- how much of the above don't you understand? You want me to use
>€ smaller words?
What a stroke.
You really don't get this, do you?
Steven B. Harris
OldSalt <Babet...@removethisHotmail.com> wrote:
>On Tue, 07 Nov 2000 20:22:52 GMT, Steven B. Harris
><sbha...@ix.netcom.com@ix.netcom.com> wrote and since I have
>Supernews, it's amazing that I could even see it:
>
>From Dr Taylor:
>>>If you sell lithium for batteries or grease, the FDA has no
>>>jurisdiction. As soon as you sell the exact same lithium for relief
of
>>>mental disorders, the FDA has jurisdiction.
>
>>Yes, you're getting it. But also if you sell lithium to prevent
>>episodes of mental disorders. Now, is this becoming more clear?
>
>Steven... perhaps using Lithium as an example isn't quite right. No
>one sells or prescribes it to "prevent" the initial episode. The
>patient is diagnosed with the problem and then the med is given for
>treatment, yes ?
Since it's not a fast treatment, something else is usually used acutely
(Tegretol, etc), and lithium is added (either immediately or later) to
be used as a preventive for further episodes.
We can haggle over the meaning of the word preventive, but as used in
medicine, there are primary and secondary preventive drugs. Primary
preventives are used to prevent a first episode, and the secondary
preventives are used to prevent further episodes after a first. In both
cases, the drug is used in asymptomatic people. A good example of a
primary preventive drug would be lovastatin in use to prevent a first
heart attack. This works even in people with fairly "normal"
cholesterols.
There are many cases of drugs used as primary preventives. If you get
hip surgery, you'll get a course of coumadin as primary preventive
against pulmonary emboli-- even if you've never had a pulmonary embolus.
The issue is confused a bit by the fact that some nutrients have been
exempted from the FDA requirements for preventives, inso far as they can
now be sold while making preventive statements on their labels, which
the FDA distances itself from ("The FDA has not evaluated this substance
for this use"). But this freedom for nutrients and herbals is through a
specific act (The Hatch Act, which the FDA fought tooth and nail). It
would be a stretcher to apply the Hatch Act to enriched O2 mixes for the
purpose of preventing bends. FDA already regulates O2 breathing for all
kinds of preventing problems (like prevention of pulmonary hypertension
if you have sleep apnea). You need a prescription to get it. If you have
to have a Rx to get enriched O2 mix to prevent PAH because you snore,
you certainly ought to need one to get enriched mix to prevent DCI
because you dive.
A few other normally over the counter meds like aspirin have been
permitted by the FDA to make preventive claims, but these are special
drug-by-drug exemptions, based on results from good controlled trials
for that particular drug.
So far as what it's used for, extra oxygen used in a dive to prevent DCS
is a lot more like coumadin than it is like aspirin-- you use it for a
short time, usually at doses which would cause lung damage or even kill
you if you used it all the time; and you use it in order to prevent a
specific episode of a bad pathophysiologic result. But remember, the FDA
even had to specifically sign off on asprin, when used for preventing
heart attacks. The change in labeling only happened after some massive
aspirin primary prevention trials, where it was shown to be effective.
If you look for similar controlled trials at the effectiveness of EAN to
prevent bends, you aren't going to find them, because they haven't been
done. There isn't even yet any good epidemiological evidence-- only
theory. Yes, I myself use the stuff because the theory looks good, but
I'd hate to prove my case for it in the standard medical/scientific way,
as a medical modality. As compared with a lot of other medical
preventive strategies, the evidence for EAN as a DCI preventive frankly
sucks. If the FDA ever looks at it with their jaundiced eye, it's going
to be off the market until studies are done. And who's gunna pay for
THOSE??
Steven B. Harris
Jammer Six <jam...@oz.net> wrote:
>In article <8u9pva$npq$1...@slb7.atl.mindspring.net>, Steven B. Harris
><sbha...@ix.netcom.com@ix.netcom.com> wrote:
>
>>€ Now-- how much of the above don't you understand? You want me to use
>>€ smaller words?
>
>What a stroke.
>
>You really don't get this, do you?
One of us doesn't, that's for sure.
I should have edited it down to 3rd grade level.
OldSalt
since I have Supernews, it's amazing that I could even see it:
>Jeezus I've been following this, and it is GREAT!!! Steve, you are
>absolutely correct, and your patience with Doing-It-Rightists like
>Jammer is commendable. I gave up on these nincumpoops understanding
>medical info long ago, and have turned my attention to unrelenting
>harassment of the cultists. Gotta love it when someone comes along
>and smacks em in the face with a hefty dose of reality. Hats off
>to Steven B. Harris, M.D. MJBMD
I'm starting to wonder if you and Dr Harris aren't one and the same.
(Yes, I know. You and your sock puppets.) He seems to have
appeared out of nowhere. He's very knowledgeable about medical
matters. The only difference is that he tends to talk about medical
matters and he's generally more polite than you. Hmmmmm.....
OldSalt
<sbha...@ix.netcom.com@ix.netcom.com> wrote and since I have
Supernews, it's amazing that I could even see it:
>Since it's not a fast treatment, something else is usually used acutely
>(Tegretol, etc), and lithium is added (either immediately or later) to
>be used as a preventive for further episodes.
I haven't seen Tegretol used for an acute psychotic episode here, and
I've got quite a few years experience working in psych. But many
patients are on it after the acute symptoms are stabilized. More
often used for acute symptoms are Haldol or Resperidal or Prolixin or
Navane or Zyprexa... etc. A high potency drug. Lithium is then
introduced and used for maintenance and often the other drugs are
stopped.
>We can haggle over the meaning of the word preventive, but as used in
>medicine, there are primary and secondary preventive drugs.
<snipping here>
Yes...I understand what you are saying. Perhaps I'm being picky by
saying that Lithium doesn't fall into this category but I don't feel
it does. It's more a maintenance drug. Carry on your discussion
here. It's interesting. Excuse my interruption.
OldSalt
<mi...@divemed.zzn.com> wrote and since I have Supernews, it's amazing
that I could even see it:
>"Steven B. Harris" wrote:
>> In theory, if the helium is for human consumption, and is intended to
>> treat OR PREVENT disease, rather than for the purpose of doing Chipmunk
>> immitations, then the answer is yes. In theory, you need a prescription.
>
> Really? Then what do you call a bartender: a pharmacist with a
>limited inventory?
What disease is the bartender preventing or treating ? I don't
understand your question Randy.
Rich Lesperance
Mike Gray <omx...@worldnet.att.net> wrote
>
> I never heard of 80% cylinders, but using a membrane or sieve might
> allow banking a resulting 80%.
>
Is this new? as of a few years ago, membranes (at least the common ones used
for scuba shops) couldn't do better than 40% or so.
Rich
Rich Lesperance
Larry "Harris" Taylor <dive...@earthlink.net>
>
> So, playing plantiff here, please explain to the jury how using a drug
> called oxygen to remove excess nitrogen from the body to prevent a disease
> called decompression sickness is exempt from Federal control of drugs.used
> in the prevention or treatment of diseases?
Playing Devil's advocate here, I could answer , it is exempt the same way
using a drug called oral rehydration solution is used to restore proper
electrolyte and fluid balance in the treatment or prevention of a disease
called dehydration.....
Or will you lock up the gatorade <g>.
Rich L
Steven B. Harris
"Larry \"Harris\" Taylor, Ph.D." <l...@umich.edu> wrote:
>Michael J. Blitch <mbli...@tampabay.rr.com> wrote in message
>news:4fiuts83h6t582im1...@4ax.com...
>> Before the blanket OSHA variance, Dr. Taylor, did you ever teach a
>> dive class while using nitrox?
>
>
>Yes, the gas used by me and my students was mixed from aviator's grade
>O2 (highest grade O2 available) and Grade J air.
By now you must be an ANDI (American Nitrox Divers International) wonk.
For those looking for more info on ultrapure gases for sport diving, I
suggest www.andihq.org
mjbl...@my-deja.com
absolutely correct, and your patience with Doing-It-Rightists like
Jammer is commendable. I gave up on these nincumpoops understanding
medical info long ago, and have turned my attention to unrelenting
harassment of the cultists. Gotta love it when someone comes along
and smacks em in the face with a hefty dose of reality. Hats off
to Steven B. Harris, M.D. MJBMD
In article <8ua4ju$lta$1...@slb0.atl.mindspring.net>,
Sent via Deja.com http://www.deja.com/
Before you buy.
Michael J. Blitch
Real life?
--
Things I'd Do If I Ever Became An Evil Overlord:
57: Before employing any captured artifacts or machinery, I will carefully read the owner's manual.
chilly
correct me if I'm wrong) but I believe she was referring to Dr. steven b.
Harris, and not your good self.
Larry "Harris" Taylor <dive...@earthlink.net> wrote in message
news:zi4O5.30657$Pw6.2...@newsread1.prod.itd.earthlink.net...
>
> "OldSalt" <Babet...@removethisHotmail.com> wrote in message
> news:f0jh0t4op0abccjl3...@4ax.com...
> > On Wed, 08 Nov 2000 00:56:12 GMT, mjbl...@my-deja.com wrote and
> > since I have Supernews, it's amazing that I could even see it:
> >
> > >Jeezus I've been following this, and it is GREAT!!! Steve, you are
> > >absolutely correct, and your patience with Doing-It-Rightists like
> > >Jammer is commendable. I gave up on these nincumpoops understanding
> > >medical info long ago, and have turned my attention to unrelenting
> > >harassment of the cultists. Gotta love it when someone comes along
> > >and smacks em in the face with a hefty dose of reality. Hats off
> > >to Steven B. Harris, M.D. MJBMD
> >
> > I'm starting to wonder if you and Dr Harris aren't one and the same.
> > (Yes, I know. You and your sock puppets.) He seems to have
> > appeared out of nowhere. He's very knowledgeable about medical
> > matters. The only difference is that he tends to talk about medical
> > matters and he's generally more polite than you. Hmmmmm....
>
>
> We are NOT the same ... I was mis-informed on .otis ..he corrected me (g)
>
>
> Everyone here has their own style ...their background (education and
> experience) is different and is reflected in the way they post ...Every
> profession has a set of vocabulary and the style of post reflects the day
to
> day manner of communication ... while a biochemist and physician have
SOME
> similar philosophies, the backgrounds and approaches to things will vary
> with respect to these disciplines.
>
> Besides, what MD would admit to being a mere Ph.D. (g)
>
>
>
> --
> "Harris"
> Larry "Harris" Taylor, Ph.D.
> Scuba Instructor, U of MI
>
>
>
>
>
>
>
Popeye
MJBMD
Wrong Doc, Doc!
Popeye
5 Bucks on Team 3
Rich Lesperance
<mjbl...@my-deja.com> wrote in message news:8ua8ba$fm0$1...@nnrp1.deja.com...
> Jeezus I've been following this, and it is GREAT!!! Steve, you are
> absolutely correct, and your patience with Doing-It-Rightists like
> Jammer is commendable. I gave up on these nincumpoops understanding
> medical info long ago, and have turned my attention to unrelenting
> harassment of the cultists. Gotta love it when someone comes along
> and smacks em in the face with a hefty dose of reality. Hats off
> to Steven B. Harris, M.D. MJBMD
>
Steven,
My condolences on your latest endorsement. Don't worry, most of us here will
still respect you in _spite_ of the fact MJB is sniffing your butt.....
Rich L
Rich Lesperance
Steven B. Harris <sbha...@ix.netcom.com@ix.netcom.com> wrote
>
> It has jurisdition over any gas mix, including EAN nitrox, which is
> sold for the prevention of a disease, like decompression illness.
Steven,
Not only am I not a lawyer, but I wholeheartedly despise them.
That being said, ISTM that using the above logic, one could say that air is
used in the prevention of asphyxiation, which would raise the ludicrous
spectre of the FDA regulating everything.
The FDA themselves (to give an example) don't touch food additives or
nutritional supplements (or possibly congress restricted them, I don't
remember). Yet you expect them to start regulating nitrox?
Rich L
Rich Lesperance
Steven B. Harris <sbha...@ix.netcom.com@ix.netcom.com> wrote
> The FDA
> a few years ago made the entire US army get rid of most of its stocks of
> frozen blood, because it didn't meet approval standards for the use it
> was intended for. That's THE U.S. army-- the guys with the tanks and
> nukes, remember? The FDA steamrollered right over them.
It's because they're such nice guys. But they had to give up their nukes
years ago, only the Navy and Air Force still have them <g>.
Rich L
Rich Lesperance
Larry "Harris" Taylor <dive...@earthlink.net>
>
> We are NOT the same ... I was mis-informed on .otis ..he corrected me (g)
>
Wrong Harris, Harris <g>. She was talking about Steven Harris.....
Rich L
Rich Lesperance
keeping one's options open.
I have to admit a personal bias, though. The calculus of the decision for me
will always lie with the 100%, and, short of the radical "expedition" diving
you and LHT have described, I will always look at a diver using 80/20 with
suspicion....
Thanks,
Rich L
Randy F. Milak <mi...@divemed.zzn.com> wrote in message
news:3A086900...@divemed.zzn.com...
> Rich Lesperance wrote:
> >
> > Randy F. Milak <mi...@divemed.zzn.com> wrote
> >
> >
> > Let me pick my words carefully - since bubble reduction is a diffusion
> > function (a significant part of which is the replacement of the N2
fraction
> > with O2), using _any_ inspired N2 will slow down the rate at which that
> > diffusion occurs (because you are diffusing into a tissue [plasma] that
> > already _has_ some nitrogen), and therefore bubble reduction is slowed.
>
> Well chosen, and it's very true. Common ground lies in the fact
> that 100% oxygen used for staged decompression is the most effective gas
> to eliminate any inert gas tissue load. I would concede, that,
> providing oxygen toxicity limits are well within an acceptable risk
> level to satisfy ones own risk management criteria, then, one should
> always choose the best gas (as defined by expedience and efficiency for
> offgassing) for all stages of the decompression regime.
>
> The EAN 80 vs 100% debates always seem to ramble on about the same
> old same old; one side claiming oxygen toxicity the other claiming that
> its not as effective at offgassing etc. etc. to ad nausea. What I
> believe, is that the diver needs to make a well defined decompression
> strategy, based on a vigilance for life preservation, injury avoidance,
> and base it on solid risk analysis. Simple fact is, is that neither gas
> is the "BEST" gas to use under EVERY given staged decompression criteria
> simply because expedience of decompression, although at the top of the
> list, is not the only criteria. Example - single, none repetitive,
> mixed gas dive with 30% or better helium content, less than 220 fsw,
> less than 60 minute bottom time, double gas switch deco with possible
> full face mask availability, then no brainer, 100% without a doubt.
> Conduct that same dive twice a day for the next six days utilizing 100%
> oxygen, then perhaps the diver should take a second look. I could take
> either side of the 100% vs EAN 80 debate and form a sound argument.
> What I wouldn't do, is close off my options.
>
> Risk management is not about one specific criteria. By the same
> token, risk management is not universal either. To a large extent, risk
> and safety are a matter of opinion and an individual's viewpoint. I
> suppose that's why we debate. For the most part, I can not actually
> take either side of an 80/20 vs 100% debate and argue it like either of
> them are the only way in the world to decompress. I could only suggest
> that divers weigh the risks they are taking against the rewards. For
> each diver, for each circumstance, the answers will be different. I
> don't swim, breath or dive for someone else and will not be so
> presumptuous as to dictate only one way, since there are several. Diver
> education is key.
>
> > I don't know enough about kinetics to express it using the proper
> > mathematical notation, but if you increase the inspired nitrogen, you
will
> > be slowing your off-gassing, even if there is _no_ net on-gassing (and I
> > agree with you, it is very unlikely for net on-gassing to happen)
>
> Everyone discusses basic interpretations of gas kinetics in terms
> of either exponential inert gas uptake and elimination, or, as
> exponential inert gas uptake followed by linear elimination; such as
> found in your carefully worded first paragraph. That's where one
> discovers that, "you will be slowing your off gassing" using less than
> 100% deco gas. Not often addressed in ascent criterion discussions are
> aspects of free phase bubble growth and what happens to them in
> different mixed gas/EAN decompressions. Why? Probably because
> supersaturation theory is much simpler to understand than bubble
> mechanics. Anyways, within that theory are interesting aspects of
> formed bubble stability during the decompression stages, that would add
> to the 100% argument over 80/20. I only mention it, because its
> something that rarely if ever, seems to get addressed (besides, it
> doesn't help my 80/20 argument at the moment either <G>).
chilly
Larry "Harris" Taylor <dive...@earthlink.net> wrote in message
news:Se5O5.30796$Pw6.2...@newsread1.prod.itd.earthlink.net...
>
> "chilly" <sla...@home.com> wrote in message
> news:vJ4O5.80526$76.14...@news1.rdc1.ab.home.com...
> > Dr. Taylor, I probably shouldn't speak for Salty (and she will certainly
> > correct me if I'm wrong) but I believe she was referring to Dr. steven
> b.
> > Harris, and not your good self.
>
>
> Sorry ...it's late, I am old (g)
>
> BUT, there is still no need to call me DR
Jammer Six
Larry \"Harris\" Taylor <dive...@earthlink.net> wrote:
>€ BUT, there is still no need to call me DR
Sure there is.
We have to have a way for the apes to know the difference between you
and Dinky Dave.
:)