Intentionally arrhythmic respiratory patterns?

[northernone]

Ok, if you've made it this far and realize it's the tec forum:

I breath-hold on scuba.

A few dozen times per dive for photography (and critter sneaking).

Generally 1.5 to 3 minutes per hold. Normal breathing after 2 recovery breaths if strenuous. Overall SAC lowers. No co2 headache after these dives.

I've never gone into a hyperventilating panic on OC. Can someone explain why not? Is a hypercapnia response that heavily conditional?

My experience isn't lining up with my reading so here's a thread of hope that someone can connect my missing pieces.

Cameron

 

[doctormike]

The most important sentence in medical school is "there is a bell curve for everything".

There are a few anesthesiologists here who can probably give you a better answer than I can (paging @rsingler or @Compressor ).

But unless you can measure your end tidal CO2, you wouldn't know what the balance of your metabolic CO2 production and elimination actually are. And even if you did know that, that, your symptoms would depend on how sensitive your capnostat and cerebral vasculature are to X level of respiratory acidosis...

 

[Compressor]

“page received.” I’m actually at work on call!!

When you hold your breath, the carbon dioxide does not leave your aleveoli and exhaled. In general carbon dioxide builds about 6-9 mm HG/min when there is no ventilation. Build up of carobon dioxide leads to what is called respiratory acidosis. The bloof pH becomes acidic. If one hold their breath and is active, the rate of buildup is even more. Carbox dioxide is a potent stimulus for breathing. Acidosis can lead to arrythmias. Hoewever, I don’t know of any data suggesting arrthymias induced by breath holding for 3 minutes. I could look it up if there is interest. Most likely there will be data in animals.

As far as panicking caused by hyperventilation, I don’t know if there is a causal relationship.

The cerebral vasculature, responds directly to the PaC02 . The more CO2, the more the vasculature dilates in the brain. And vice versa. However when PaC02 reaches about 80 mm HG, the maximal vasodialtation occurs. If the PaCO2 is reduced to about 20-25 mm HG, the vasculature is constricted maximally. Both are dangerouse and non physiologic. The former caused increase brain pressure and latter may cause cerebral ischemia. The brain like constant blood flow. It autoregulates its flow based on need. Areas needing more flow because of higher activity, will get perefential blood flow and vice versa.

Hope this answers some questions.

 

[doctormike]

I think that the OP was using the term "arrythmic respiratory pattern" to describe his habit of "skip breathing", not referring to a cardiac arrythmia...

Thanks, doc...!

 

[rsingler]

I'm not sure @northernone was implying cardiac arrhythmia from hypercarbia. I think he was discussing his arrhythmic breathing pattern: cleansing breaths, breath-hold, cleansing breath.
Any lowering of your measured SAC should be solely due to decreased dead space exchange, and large tidal volume when you DO breathe. It's efficient. I'm not sure you can adequately dump all of the carbon dioxide that accumulates during that 1.5-2 minute breath hold with just two breaths, but I suspect your next few breaths are fractionally larger, and it's hard to quantify how much more you're breathing than you think.

But your CO2 has to remain relatively stable. @northernone , you imply some decreased sensitivity to hypercarbia, and I suspect that's a trained response given the near or actual CO2 hits you have encountered at depth. Mild hypercarbia doesn't freak you out.

But you can't actually lower your true SAC at all. Your metabolism is what it is, and exercise is the only modifier. What you CAN do is make your breathing more efficient. Every breath exchanges dead space. More breaths just waste tank air, exchanging gas that was sitting in dead areas (regulator, oropharynx, trachea, bronchi). So folks that improve their measured SAC do two things, usually: they relax and generate less CO2 with more streamlined diving and a Zen approach to the dive, and they breathe more efficiently. I suspect that what you describe is an extreme version of the latter.

Oh, @doctormike beat me to it.

 

[northernone]

Thank you! Each.

Goodness, I'll humbled by the outpouring of freely shared expertise.

I'll continue to digest these articulate and clear replies as my own private reference again after some more sleep.

Warmest regards!
Cameron

 

[Johnoly]

..A few dozen times per dive for photography (and critter sneaking)....

A slightly tangent topic shift....I dive with plenty of pro photographers. On shark and Goliath photo shoots they all dive rebreathers and yet we're only in about 70 foot of water. (not tech deep at all). One of the reasons they say is certainly the lack of bubbles so they can get to just inches of their subjects. But also more important to them is the electrical impulse's their bodies & equipment give off and the fish pick up. They maintain that you can't stop those electrical bursts which are kinda like a 'crack of lighting' and spook the fish. It is much more desirable to maintain a 'level consisant buzz' that the fish subject get's used to. The RB allows them to calmly continuously breathe, maintain a steady body electrical output and get closer. One has taken to no-strobes and just uses video lights since the strobe pops were still pushing off subjects. The debate is still on about HECS,

 

[doctormike]

A slightly tangent topic shift....I dive with plenty of pro photographers. On shark and Goliath photo shoots they all dive rebreathers and yet we're only in about 70 foot of water. (not tech deep at all). One of the reasons they say is certainly the lack of bubbles so they can get to just inches of their subjects. But also more important to them is the electrical impulse's their bodies & equipment give off and the fish pick up. They maintain that you can't stop those electrical bursts which are kinda like a 'crack of lighting' and spook the fish. It is much more desirable to maintain a 'level consisant buzz' that the fish subject get's used to. The RB allows them to calmly continuously breathe, maintain a steady body electrical output and get closer. One has taken to no-strobes and just uses video lights since the strobe pops were still pushing off subjects. The debate is still on about HECS,

The only reason I dive is to take photos, I'm rarely without a camera. I gotta say, I LOVE my rebreather, but I have been underwhelmed with this particular claimed benefit. I don't see a huge difference in the sea life reaction between OC and CCR. I'm a pretty quiet and calm diver. Maybe it's more of an issue with big animals?

My theory is that fish have evolved to be aware of large predators that don't blow bubbles. Hard to imagine that they wouldn't notice me just because I'm not on OC. But maybe I was expecting too much...

 

[Compressor]

But your CO2 has to remain relatively stable. @northernone , you imply some decreased sensitivity to hypercarbia, and I suspect that's a trained response given the near or actual CO2 hits you have encountered at depth. Mild hypercarbia doesn't freak you out.

Agree 100%.. Right on the money.

Is a hypercapnia response that heavily conditional?

.

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 suspect you are so relaxed in the water , you are able to control your responses. We see that in free divers.

I enclosed an article on this topic of conditioning. It was done in rats. I did not find any studies in humans but only looked for 1/2 hour or so.

 

[Johnoly]

... Maybe it's more of an issue with big animals?..

I'm glad I'm not a photog and once at the sites told to stay out of the picture and watch their backs. What they do on their "speed date" is what seals the deal. I can't help with that.