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At 12:30 PM 12/6/94, David Doolette wrote:
>>What would happen if a (or possibly two) catheter(s) were inserted into an
>>artery that would send it through an oxygenator?  As long as the oxygenator
>>removed CO2, you wouldn't feel the need to breathe.  Since you're not
>>breathing, you don't need a diluent to bring the total pressure of an
>>inspired gas high enough to allow your chest muscles to draw the gas into
>>your lungs against the ambient pressure against your thorax.  There are the
>>problems of preventing clots from being circulated, but I believe that
>>problem has been somewhat solved for surgical procedures.
>
>CO2 and to a lesser extent O2 modify the rate of breathing, but respiratory
>rhythm is primarily under control of groups of respiratory neurons in the
>medulla (that is a bit of your central nervous system) so you wouldn't stop
>breathing.

Hmm, there's something that's fundamentally different here than I
understood the breathing reflex.  It was my understanding that what
triggered the "urge to breathe" was the level of CO2 in your bloodstream as
sensed by receptor sites in the medulla.  It is for this reason that
hyperventilation (or pre-breathing pure O2) staves off the urge.  If the
CO2 level was never allowed to build up to the level that triggers
inspiration, why would the medulla require one to take a breath?

Obviously there's something I don't understand here, but I'm not sure where
to go looking for more information on the process controlling inspiration.

>
>>Since there is no diluent, there should not be any problems with narcs,
>>DCI, HPNS, etc.  In fact, the diver wouldn't need anything to cover their
>>mouth.
>
>You would not get narcosis or DCI but you would get HPNS as the latter is
>not related to inspired gases.  The same is true, however, for liquid
>breathing.
>

Hmmm... I thought HPNS was related to Helium and presure.  However, I'm on
really shakey ground there.  Hi Ho, Hi Ho, it's off for more study I go!

>regards,
>
>David Doolette
>ddoolett@me*.ad*.ed*.au*

Thanks for your presence, David!

     -- Kevin --

"I'll get around to it today --
          For sufficiently large values of 'today'"

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