Types of Asthma

[damon harvey]

INTRODUCTIONTo properly treat asthma it is important to classify a
patient's current severity to determine the appropriate therapy
choices; therefore a stepwise approach is used. Asthma is classified
as either mild intermittent or persistent. Persistent asthma is
further classified as mild, moderate or severe. Regardless of the
classification there may be periodic exacerbations ranging from mild
to severe which can make therapy quite challenging and requires the
patient, patient's family and physician to watch closely for any
changes. Even a mild intermittent asthmatic can have severe life
threatening episodes. These episodes may be separated by months or
years with no symptoms at all. A patient's asthma classification
certainly can and probably will change (in either direction) over time
so just one symptom characteristic of a given classification level is
enough to raise a patient into that severity class thereby providing
the best control possible. Due to the overlapping nature of the
categories if the classification seems a bit fuzzy, the patient should
be staged in the highest class for which any characteristics are seen.
LUNG FUNCTION TESTING Before beginning a discussion of the
classification of asthma it is important to understand the common
tests that are used to determine a patient's level of pulmonary
function. It is very helpful to perform at least a basic pulmonary
function test and not base a diagnosis of the severity (type) of
asthma only on the signs and symptoms presented. The most common
office test is spirometry which measures the maximal volume of air
forced on exhalation from the point of maximum inhalation (forced
vital capacity (FVC) and the volume of air exhaled during the first
second of the FVC (FEV1). A patient can also use a peak flow meter at
home to check the peak expiratory flow (PEF) variation between morning
and in the afternoon (after using a short acting beta-agonist inhaler)
to get the PEV variability. To determine the predicted PEF get a peak
flow reading in the afternoon when the patient feels as close to
normal as possible (even if a couple of puffs of a short acting beta-
agonist are needed). These two PEV markers will be referred to in the
subsequent sections.
MILD INTERMITTENTMany asthma patients fall into the mild intermittent
category. This group of patients may be symptom free for extended
periods of time or may have short exacerbations on a fairly frequent
basis. To be classified as mild intermittent a patient will have
symptoms such as wheezing or shortness of breath no more than twice
per week and nighttime symptoms no more than twice per month. The
symptomatic exacerbations may last from a few hours to a maximum of a
few days (although the severity may vary from one episode to the
next). Between episodes there will be no symptoms and lung function
tests will be normal. In this group lung function tests will show a
PEF that is at least 80% of the predicted (best afternoon) value and
have a variability of less than 20% (between morning and afternoon).
This type of asthma patient usually will not require medication on a
daily basis and can use a short acting rescue inhaler such as
albuterol if needed for symptomatic control. A rule of thumb is that
if the rescue inhaler is used more often than twice per week or if a
canister lasts less than a month then there may be need for some type
of controller medication. An occasional flare-up can be treated with a
short course of steroids such as prednisone. A special class of
asthmatics should be mentioned here, these are those with exercise
induced asthma. A patient with exercise induced asthma typically will
only be symptomatic during times of physical stress and usually can be
controlled by pretreating with a short acting inhaler such as
albuterol or even cromolyn. A diagnosis of exercise induced asthma
although often easy to control should not be taken lightly for without
pretreatment to prevent symptoms an attack could become a medical
emergency.
MILD PERSISTENTThis class of asthma presents with patients who have
symptoms more often than twice per week but less than once per day.
Mild persistent asthmatics often have nighttime symptoms more often
than twice per month but less than once per week. Lung function
testing would show a PEF of greater than 80% of the predicted value
which is similar to mild intermittent but with the difference of more
variability in the 20 to 30% range. Most mild persistent asthmatics
can be best treated with inhaled corticosteroids with a rescue inhaler
used only on an as needed basis. Other treatment options exist but
will not be covered here. This is the class of asthmatic that seems to
often be mis medicated because although a rescue inhaler will often
keep many patients essentially symptom free it will do nothing to
decrease the inflammation that is a component for even the mild
persistent asthmatic. This point should be reinforced: you do not
treat persistent asthmatics with a short acting inhaler as mono
therapy and the rule of thumb should be considered and a patient
considered not under suitable control if they exceed one inhaler per
month.
MODERATE PERSISTENTPrior to treatment the moderate persistent
asthmatic typically has daily symptoms with exacerbations at least
twice per week on average. These flare-ups affect normal daily
activity and often last for a number of days. Nighttime symptoms are
seen more often than once per week. Lung function tests will show a
PEF in the range of 60 to 80% of the predicted value with a
variability of greater than 30%. Like the mild persistent asthmatic
there are many moderate persistent asthmatics that are not being
treated correctly. A short acting rescue inhaled used as monotherapy
for an asthmatic at this level is simply bad medicine. It must be
remembered that any one of the classifying symptoms is enough to place
a patient in a given level so for example if a patient has nighttime
symptoms more than once a week (one of the features of this class)
then they should be considered to be moderate persistent even with out
any of the other features. Remember if uncertain where to stage a
given patient the physician should move in the direction of higher
rather than lower classification. The moderate persistent asthmatic is
usually best treated with a low to medium dose inhaled corticosteroid
in combination with a long acting beta-agonist. Other treatment
options exist but this is the best for most moderate persistent
patients. Once again it needs to be reinforced that excessive use of
short acting inhalers on a regular basis is a sign of poor control and
the need for reevaluation of the treatment plan!
SEVERE PERSISTENTThis is the highest classification of asthma patient.
The severe persistent asthmatic is always symptomatic with the ability
for only limited physical activity. Both daytime and nighttime
exacerbations are frequent and can last for extended periods. Lung
function testing will show a PEF of 60% or less of predicted value
with a variability of greater than 30%. The severe persistent
asthmatic is usually best treated with a high dose inhaled
corticosteroid combined with a long acting beta-agonist. To achieve
long term control oral corticosteroids are often needed with the goal
of achieving control with the lowest daily dose possible thereby
reducing systemic side effects.
CONCLUSIONThis article has focused on the importance of correctly
determining the type (category) of asthma that a patient has thereby
providing their physician the information needed to deliver optimal
therapy. The levels can certainly change (either up or down) over time
because asthma categories are not static.
Although as current and accurate as possible, the information
contained in this article or provided to you by the author in an email
or any other manner, may not relate to your particular medical
condition and is not intended to be used in the diagnosis or treatment
of any specific medical condition. Always refer to your healthcare
provider before making any changes in your treatment plan.