Intentionally arrhythmic respiratory patterns?

[The Chairman]

Skip breathing to take a picture is fine. It's more of a simple pause and hopefully you don't occlude the glottis. I do this all the time, and it's never done as an attempt to reduce my SAC (DAC). It's done to delay the bubbles that will scare your subjects. I also choose a rebreather to accomplish this.

Carbon Dioxide is a potent stimulus for initiating a breath. Resisting it will cause a sympathetic nervous system response (like a fight or flight response).

I know of two cave divers who systematically skipped breathed to the point of panic often enough that it became a psychosomatic response to diving and ultimately caused them to leave the sport. They both started to panic whenever they tried to descend. While this is extreme, it shows the danger of pushing your body too far on a consistent basis. What was really peculiar is that both reached out to me within about 6 months in 2003. My old moniker "NetDoc", often confused people into thinking that I was a medical doctor and I used to get all sorts of people asking me for advice. Obviously I asked both to seek advice from real doctors. That's not what @northernone is discussing here.

 

[doctormike]

Skip breathing to take a picture is fine. It's more of a simple pause and hopefully you don't occlude the glottis. I do this all the time, and it's never done as an attempt to reduce my SAC (DAC). It's done to delay the bubbles that will scare your subjects. I also choose a rebreather to accomplish this.

Even briefly occluding the glottis isn't an issue if you are at constant depth, but I agree that it's better not to develop that habit!

Remember the most important sentence from medical school, upthread.... some people do have problems with skip breathing, depending on their personal sensitivity to respiratory acidosis. Ironically, hyperventilating can also result in hypercapnea if the tidal volume is low (fast, shallow breaths), because of the relative contribution of dead space ventilation. And hypercapnea doesn't always present as headache or panic.

 

[RyanT]

As our actual experts alluded to, hypercapnia is a stimulus to breathe (and more rapidly), but there seems to be a lot of individual tolerance to CO2. I found a paper recently, showing breathing response rates to CO2 retention (sorry I don't have it handy, so I don't remember the details). In that study, some individuals exhibited a marked increase in their respiratory rate and others did not. I asked our respiratory physiologist about this and he was telling me that aside from CO2, stretch receptors in the thoracic cavity can be a strong influence on the trigger to breathe. For example, he said most people can substantially increase their breath hold time simply by exhaling into a plastic bag and rebreathing that same gas. It's the movement of the thoracic cavity that reduces the trigger to breathe. Further, if they place bands around a person's chest (restricting expansion of the ribs), some people are comfortable with a restricted tidal volume while it induces panic in others. So my point again, there is a lot of individual variation, which I find quite fascinating.

 

[The Chairman]

It's the movement of the thoracic cavity that reduces the trigger to breathe.

Interesting. I find that switching between my chest and abdomen reduces my desire to breathe when I'm free diving.

 

[Compressor]

This is very interesting topic as the respiratory drive is an involuntary one. We don't think about breathing unless we are having trouble with shortness of breath like in asthma or COPD or other medical conditions. As for divers who skip breath, they have to make a conscious effort to hold their breath.

 

[RyanT]

@The Chairman I suppose there's that bell curve that @doctormike was talking about!

@Compressor, yes, a fascinating topic indeed. Assuming a really relaxed dive, I have a natural tendency to skip breathe. I get so relaxed that it almost feels like too much effort to take a breath, and it's more comfortable to just pause. This never occurs on land even when I'm at complete rest. Fortunately, if I hold it too long U/W, that urge does appear!

 

[johndiver999]

Freedivers have special training regiments that are specifically designed to reduce sensitivity to co2. .. look up co2 tables.

They have two different types of protocols, one is intended to habituate to low oxygen and the other different “table” is to address carbon dioxide, if my understanding is correct. I don’t do them..

I think deliberate and significant skip breathing of over a minute is a very danergous activity and is specifically not
Recommended.

Anybody who can breath hold for 3 minutes and fully recover in 2 or 3 breaths is exceptional and would probably be considered elite. Skip breathing of this magnitude is not
something to be casually emulated.

Possibly the higher partial pressure of oxygen makes it easier, but co2 production would be the same as the surface.

 

[rsingler]

Possibly the higher partial pressure of oxygen makes it easier, but co2 production would be the same as the surface.

This.

 

[Rooster59]

What if you blackout and your reg drops out of your mouth?

 

[rsingler]

What if you blackout and your reg drops out of your mouth?

That's the point that @johndiver999 was making above. Skip breathing at depth is less likely to result in a blackout due to ambient pressure of inhaled air: there are ?double, ?triple, ?quadruple the number of oxygen molecules in your lungful, but your metabolic requirement is the same. So if you could hold your breath for two minutes at the surface, you could theoretically hold it for 6 minutes at 66'.
EXCEPT that your CO2 production continues all the while. The urge to breathe becomes overpowering at modest increases in blood pCO2. And if you condition yourself to ignore that, the risk of changes in judgment due to hypercarbia, or of a cardiac arrhythmia, or of sudden panic becomes significant.
Hence, the subtle advice by @The Chairman and @johndiver999 - don't do that!