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Re: Lung ventilation rates

Gautam Majumdar wrote:

> Chronic retention of carbon dioxide (hypercapnia) is compatible with
> life and occurs in human patients with congenital cyanotic heart
> disease and chronic obstructive lung disease. These people do not
> develop life threatening acidosis because kidneys are perfectly
> capable for controlling the acid-base balance. In such a condition
> hypercapnia loses its effect and hypoxia alone drives the
> respiration.

    Yeah, but isn't this an abnormal condition?  The kideys are being 
used as an emergency back up system, but they aren't normally controlling 
the acid base balance to this extent, are they?  How could they keep 
this increased level of activity if the problem is not corrected?  I think 
that the CO2 is NORMALLY the the driving force of respiration tells you 
something.  I note that evolution has not seen fit to provide some sort of 
back up system to control hypoxia (altering the oxygen content of the air they
inhale isn't something most organisms can do), presumably because it isn't as 
common a problem.  

LN Jeff