I was chatting w/ someone recenty and they mentioned that they knew someone who would stay underwater for "a long time" by breathing out air into a pocket and then breathing it back in. After thinking about this a bit, I concluded that it might be plausible. Dangerous, but plausible. I figured I'd run this past folks to see if my reasoning is correct.
Before reading any further, note that this technique, if it works, is probably a great way to black-out and die.
- Don't try this at home
- Don't get all clever "try it at the local public pool instead".
Water absorbs Co2 pretty readily. If you breathed out into a pocket that had a large surface area, wouldn't some of the Co2 diffuse into the surrounding water? Could enough Co2 diffuse in this way to suppress the breathing urge a bit? What if you used "bubbling" to overcome surface tension, increase area etc. Basically, this would be a crude re-breather that didn't need sofnolime ... For the limnologists out there, could you actually pick up some O2 if you did this little circus act in the metalimnion of a lake with a positive heterograde profile (note: I have no clue what this means)?
The rate of diffusion should go up with depth (assuming area remained constant) and also go up with rising levels of CO2 since both factors increase partial pressure of CO2. Since CO2 diffuses into water at 18x the speed of O2, the loss of O2 should be small in comparison to the loss of CO2 (note, Co2 is 22x more soluble than O2, but the larger molecule size slows down the rate of diffusion -- the assumption here is that the CO2 dffusion will not change the concentration of the body of water in any significant way).
Doest the act of breathing itself satisfy the urge a bit, even if there is no net change in gas composition? I realize here that breathing may have an undesireable effect of raising the heart rate, overall metabolism etc, but that is a little beside the point...
It seems clear that this technique, even if there is any merit to it, would not help a champion apneist stay under longer, since the reduction in blood pH helps with tolerating low Co2 levels. However, it seems like it might allow someone who is CO2 "intolerant" to stay under longer than they could otherwise.
I just want to repeat that if this worked, it would be extremely dangerous because the increased comfort level would be deceptive and the reduced Bohr effect would increase the likelihood of passing out -- so I'm asking this question from a theoretical viewpoint and not advocating it as a useful technique. I just thought that it was an interesting idea, and I wondered if my rationale was right.
Before reading any further, note that this technique, if it works, is probably a great way to black-out and die.
- Don't try this at home
- Don't get all clever "try it at the local public pool instead".
Water absorbs Co2 pretty readily. If you breathed out into a pocket that had a large surface area, wouldn't some of the Co2 diffuse into the surrounding water? Could enough Co2 diffuse in this way to suppress the breathing urge a bit? What if you used "bubbling" to overcome surface tension, increase area etc. Basically, this would be a crude re-breather that didn't need sofnolime ... For the limnologists out there, could you actually pick up some O2 if you did this little circus act in the metalimnion of a lake with a positive heterograde profile (note: I have no clue what this means)?
The rate of diffusion should go up with depth (assuming area remained constant) and also go up with rising levels of CO2 since both factors increase partial pressure of CO2. Since CO2 diffuses into water at 18x the speed of O2, the loss of O2 should be small in comparison to the loss of CO2 (note, Co2 is 22x more soluble than O2, but the larger molecule size slows down the rate of diffusion -- the assumption here is that the CO2 dffusion will not change the concentration of the body of water in any significant way).
Doest the act of breathing itself satisfy the urge a bit, even if there is no net change in gas composition? I realize here that breathing may have an undesireable effect of raising the heart rate, overall metabolism etc, but that is a little beside the point...
It seems clear that this technique, even if there is any merit to it, would not help a champion apneist stay under longer, since the reduction in blood pH helps with tolerating low Co2 levels. However, it seems like it might allow someone who is CO2 "intolerant" to stay under longer than they could otherwise.
I just want to repeat that if this worked, it would be extremely dangerous because the increased comfort level would be deceptive and the reduced Bohr effect would increase the likelihood of passing out -- so I'm asking this question from a theoretical viewpoint and not advocating it as a useful technique. I just thought that it was an interesting idea, and I wondered if my rationale was right.
