Active/passive circuits

[in...@ventusers.org]

Hello, thanks for your comments about surge protectors. Yes, Dan, I agree with your comment: "I would hope that if they are really necessary in order to prevent damage to the vent that the manufacturers would supply one with each vent." The vent user appreciated hearing from you all-the voice of experience. 

Here is another question that could use an explanation from experience users vs a manual.  What is the difference between an active and a passive circuit? Someone trying out the Trilogy 100 was asked which they wanted/needed.

Joan L. Headley, IVUN 

[in...@ventusers.org]

Hi, I am posting an explanation from the Clinical Education Manager of Newport Medical. Thanks Cyndy!

 

"Active circuit" implies that there is an exhalation valve in the circuit and that valve is used in conjunction with flow delivery to control inspiration/exhalation of breath delivery and hold PEEP pressure in the circuit in between breaths if the machine is set to deliver PEEP.  If a mask is used in place of a trach tube, the mask is usually required to be non-vented (usually blue elbow). The mask should be relatively leak free and not contain an anti suffocation valve. Pressure and volume ventilation are used interchangeably with this kind of system and they are used with or without PEEP.

 

"Passive circuit" implies that there is just a length of tubing between the machine and the patient and no exhalation valve.  The system must be vented so extra gas that is delivered from the machine can escape and also, most importantly, so the patient can exhale.  The venting aspect of this system is usually accomplished with some kind of swivel or elbow that contains holes.  If a mask is used, the mask might also contain holes.  Also there is usually some kind of anti suffocation valve so the patient can still breathe if gas delivery stops (not needed on the active system because the exhalation valve serves this purpose).  Inspiration/exhalation is managed by regulating the gas flow to the patient.  Pressure (like PEEP) is held in the system in between breaths to make sure that the carbon dioxide that the patient exhales will go out through the vents and not be re-inhaled.  It is most common to use pressure ventilation with this kind of system and it is always with PEEP.  Inspiratory pressure and expiratory pressure are usually called IPAP (inspiratory positive airway pressure) and EPAP (expiratory positive airway pressure).