Peak flow and FEV1 (Forced Expiratory volume in 1 second) are both
dependent on the airway pressure you can build up with your
respiratory muscles, and the airway resistance.  In fact flow rate is
given by the pressure difference across the airways,  divided by
resistance of the airways.    In reality the peak flow therefore
depends on how hard you are trying to blow, the strength of your
respiratory muscles and the airway resistance, although it is
generally considered to reflect only airway resistance.  That's
because the other two are unknown quantities.  You need special
apparatus to measure them.

The matter is further complicated by the fact that airway resistance
is affected by swelling and blocking of the airways as a result of
inflammation,  which is the inflammatory component of asthma,  and
bronchospasm, which is due to the constriction of the small muscles in
the walls of the bronchioles.  

From the Buteyko perspective, bronchospasm is not a disease at all,
but the result of a shortage of CO2 caused by hyperventilation.  It is
well known that CO2 shortage causes spasm in these muscles, whether it
is in the bronchioles,  arterioles,  gut, etc....

From a totally teleological point of view this makes complete sense
too.  Ask your doctor, (or any of the "experts" on this list,)  what
the function is of these little muscles.  Why do we have them at all?
It is already well known that they are mainly under local control
(rather than controlled by the central nervous system) .  In other
words,  they are trying to get ventilation evened out throughout the
lungs for optimal transfer of gases between blood and atmosphere.  So
when they are all over ventilated they all constrict the airways.

In the case of asthmatics these little muscles perform their function
very well as a result of genetic predisposition.  In fact, Gayrard
(Ref 1.)  found that in the case of asthmatics, a single deep breath
of the type you make in a peak flow test, will increase   specific
airway resistance by 70% .

Again I emphasize that this is the Buteyko perspective, which
basically interprets the Peak flow and FEV1 test as telling you how
good your bronchioles are at pretecting you from hyperventilation.
From this perspective they have no value in quantifying  any disease.

Perhaps more important is to understand that your body is not a
furnace.  You don't get more performance out of it if you blow more
oxygen into it.  In fact,  since your respiratory system  regulates
CO2 level rather than Oxygen,  it is more important to raise your
average CO2 level, or rather the level about which your CO2 is
regulated..  You will gain hugely in performance and endurance,
because you will need a lot less air for the same amount of exercise.

Peter Kolb
Biomedical Engineer

pkolb@wt.com.au
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Free information provided by grateful ex-asthmatics

   http://www.wt.com.au/~pkolb/buteyko.htm

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