Question Decreasing the Breathing Reflex....Possible?

[Sure Squintsalot]

I remember some experiment from the early 70s in which a lab rat was effectively "drowned" in some aqueous solution saturated with oxygen. Because the dissolved oxygen easily diffused through the aelveolar membranes and into the rat's bloodstream, and the carbon dioxide easily diffused the opposite direction, the rat did not experience the need to breathe in and out. Completely immersed in that 2 liter aqueous/oxygen bath, the rat survived about 3 hours. It died afterwards because it was impossible to remove fluid from the deep lungs.

Can anyone explain why diving with enriched air (or even with pure oxygen) doesn't lessen the breathing reflex? If it were possible to maintain reserve CO2 in the lungs far below normal concentrations, why wouldn't that decrease the reflex?

Don't record-chasing freedivers experience some elimination of that reflex as they hold the torpedo weight and plummet to high pressure depths where oxygen is literally cold-pressed through aelveolar membranes?

 

[johndiver999]

Because the urge to breathe is not caused by oxygen. The body monitors, primarily carbon dioxide levels instead.

 

[BRT]

You can learn to ignore the CO2 to a certain extent. And get narcosis and headaches.

 

[Duke Dive Medicine]

I remember some experiment from the early 70s in which a lab rat was effectively "drowned" in some aqueous solution saturated with oxygen. Because the dissolved oxygen easily diffused through the aelveolar membranes and into the rat's bloodstream, and the carbon dioxide easily diffused the opposite direction, the rat did not experience the need to breathe in and out. Completely immersed in that 2 liter aqueous/oxygen bath, the rat survived about 3 hours. It died afterwards because it was impossible to remove fluid from the deep lungs.

Can anyone explain why diving with enriched air (or even with pure oxygen) doesn't lessen the breathing reflex? If it were possible to maintain reserve CO2 in the lungs far below normal concentrations, why wouldn't that decrease the reflex?

Don't record-chasing freedivers experience some elimination of that reflex as they hold the torpedo weight and plummet to high pressure depths where oxygen is literally cold-pressed through aelveolar membranes?

Is this the study you're thinking of? The rats still experienced the need to breathe. Respiration is primarily triggered by CO2 level in the blood.

Best regards,
DDM

 

[jborg]

It seems like the WoB would be terrible... I guess "breathing" would be handled by some kind of forced circulation via intubation?

 

[Khoujo1]

CO2 is the reason we have the drive to breathe; specifically the PaCO2 in the bloodstream. It is metabolized to an acid that diffuses into the cerebrospinal fluid that then is sensed by the medullary system and lower brainstem. One cannot consciously turn this off. This is why critically ill patients on a ventilator will be apnea if overventilated and have their PaCO2 driven to low levels; the apnea allow for increased levels in the lungs and subsequent increased acid in the CSF. This then stimulates the drive to breathe.

 

[iliketopetsharks]

CO2 is the reason we have the drive to breathe; specifically the PaCO2 in the bloodstream. It is metabolized to an acid that diffuses into the cerebrospinal fluid that then is sensed by the medullary system and lower brainstem. One cannot consciously turn this off. This is why critically ill patients on a ventilator will be apnea if overventilated and have their PaCO2 driven to low levels; the apnea allow for increased levels in the lungs and subsequent increased acid in the CSF. This then stimulates the drive to breathe.

My urge to breathe relies on a lackmus paper test?
Crazy stuff

 

[Sure Squintsalot]

Is this the study you're thinking of? The rats still experienced the need to breathe. Respiration is primarily triggered by CO2 level in the blood.

Best regards,
DDM

Cool article. Thanks for the link. The related articles are of interest as well. It's notable that there's some interest in field.

I guess I remember an aqueous solution of some sort being used specifically on rats. I'll have to spend some time digging around the internet.

Because the urge to breathe is not caused by oxygen. The body monitors, primarily carbon dioxide levels instead.

...and yet a fully developed fetus in the womb, prior to birth, with fluid-filled lungs, has no reflex to breathe.

 

[Angelo Farina]

This thread mixes two different topics: liquid breathing and breathing stimulus.
I am not aware of any connection between these two topics.
My knowledge of liquid breathing is very limited, indeed, not exceeding what one can learn on the wikipedia: Liquid breathing - Wikipedia.
Instead I have some knowledge on methods for diminishing or entirely suppressing the breathing stimulus, as I was trained to free diving, back in the seventies.
At that time it was generally considered useful to teach free divers about these methods, which allow to extend the time spent breath holding.
But they also expose to serious risks of anoxy, which I experienced twice, passing out while training in a pool.
The breathing reflex can be suppressed acting on two factors:
1) reducing the amount of CO2 in the body by long and deep hyperventilation.
2) Increasing the threshold of CO2 concentration which triggers the reflex, by training the body to withstand progressively higher CO2 concentration (breath holding just after intense muscular efforts).
Albeit the two things require completely different, opposite training procedures, the end result is that a free diver is made capable of burning all the oxygen in his lungs before feeling the need to breath.
And this yields to passing out, which can be very dangerous if there is no proper surveilliance and fast rescue.

 

[Duke Dive Medicine]

Cool article. Thanks for the link. The related articles are of interest as well. It's notable that there's some interest in field.

I guess I remember an aqueous solution of some sort being used specifically on rats. I'll have to spend some time digging around the internet.


...and yet a fully developed fetus in the womb, prior to birth, with fluid-filled lungs, has no reflex to breathe.

You're most welcome. Re fetal breathing, the fetus is supplied with oxygen and has CO2 removed via the placenta and the mother's lungs, so has no physiologic need or drive to breathe. Still, there is some movement of amniotic fluid in and out of the lungs: Fetus Breathing - an overview | ScienceDirect Topics

Best regards,
DDM