Should I breathe quickly during safety stop

[matt_w]

I think I disagree with some of the comments.. For a simple safety stop, just relax and breath normally.

When I do a deco stop for more than 4-5 min. I do something different. After 4-5 minutes of hanging at a deco stop my breathing rate and metabolism is pretty slow. I deliberately try to do short periods of exercise during deco to improve blood flow to the extremeties.. I move shoulders, elbows and also do periods of light swimming until i feel the slightest onset of fatigue in my thighs. Then resume total resting.

This activity improves blood flow, naturally increases respiration and heart rate.. We have some anecdotal evidence that not moving your arms and keeping the elbow bent during the entire deco can cause problems. I even try to switch hands if I am holding something and try to make sure my hands and wrists get a little movement and are not fixed clutching something during the entire deco.

I do a lot of those things because I get bored. Good discussion on this last year: http://www.scubaboard.com/forums/archive/index.php/t-322301.html

Short answer was that mild exercise may have benefits, but artificially altering your breath patterns has more negative effects then potential benefits.

Matt

 

[Skydiver1]

And I 'll add that if they can't they should not be teaching. I'd also add that any reasonably well trained OW diver should be able to answer it also. It's basic stuff.

I did okay in my OW training but I must not have been well trained.

My understanding is that the lower partial pressure of the breathing gas during a shallow stop creates a gradient and the resulting off gas from tissues etc then occurs. I know a safety stop is not mandatory and 3 minutes is a fairly arbitrary number.

It was more a theoretical question of why greater diffusion of gas in the lungs (from deeper and quicker breathing) would not result in an increased rate of nitrogen release from tissues. Maybe you could inform me?

 

[boulderjohn]

I
It was more a theoretical question of why greater diffusion of gas in the lungs (from deeper and quicker breathing) would not result in an increased rate of nitrogen release from tissues. Maybe you could inform me?

It's not a bad question, and it is not normally covered in OW training.

What you describe will happen to a very small degree. When you inhale, you have a specific partial pressure of nitrogen in the air in your lungs. The gradient between what is in your lungs and what is in your blood determines the rate at which you off-gas. The longer the air is in your lungs, the more the nitrogen in your blood will have diffused into it. That will slow down the rate of diffusion. To carry it to an absurd extreme, if you were to keep that same breath of air in your lungs long enough, you would achieve equilibrium between your lungs and the blood, and no more off-gassing will occur.

the difference between normal breathing and more rapid breathing, on the other hand, is inconsequential in this regard. The partial pressure will not change enough by more rapid air exchanges to provide any appreciable benefit, and that benefit will be more than offset by the other problems you create, as mentioned by others.

 

[Tortuga68]

I did okay in my OW training but I must not have been well trained.

My understanding is that the lower partial pressure of the breathing gas during a shallow stop creates a gradient and the resulting off gas from tissues etc then occurs. I know a safety stop is not mandatory and 3 minutes is a fairly arbitrary number.

It was more a theoretical question of why greater diffusion of gas in the lungs (from deeper and quicker breathing) would not result in an increased rate of nitrogen release from tissues. Maybe you could inform me?

Maybe you could read post #9

 

[Skydiver1]

It's not a bad question, and it is not normally covered in OW training.

What you describe will happen to a very small degree. When you inhale, you have a specific partial pressure of nitrogen in the air in your lungs. The gradient between what is in your lungs and what is in your blood determines the rate at which you off-gas. The longer the air is in your lungs, the more the nitrogen in your blood will have diffused into it. That will slow down the rate of diffusion. To carry it to an absurd extreme, if you were to keep that same breath of air in your lungs long enough, you would achieve equilibrium between your lungs and the blood, and no more off-gassing will occur.

the difference between normal breathing and more rapid breathing, on the other hand, is inconsequential in this regard. The partial pressure will not change enough by more rapid air exchanges to provide any appreciable benefit, and that benefit will be more than offset by the other problems you create, as mentioned by others.

Thanks, that makes sense.

 

[Jax]

:focus:

My understanding is that the lower partial pressure of the breathing gas during a shallow stop creates a gradient and the resulting off gas from tissues etc then occurs. I know a safety stop is not mandatory and 3 minutes is a fairly arbitrary number.

It was more a theoretical question of why greater diffusion of gas in the lungs (from deeper and quicker breathing) would not result in an increased rate of nitrogen release from tissues. Maybe you could inform me?

According to popular theory, offgassing occurs at different rates in different tissues. The tissues will load (on-gas) at a certain rate, and off-gas at a certain rate. To categorize tissues according to their speed of off-gassing, the theorists have opined that different tissues belong in different compartments, and this compartmentalizing can be used to estimate the total body off-gassing.

Breathing will simply exchange the gas in your lungs. The gas in your lungs will consist of whatever was off-gassed by the tissues. The exchange of the gasses from the blood to lungs is not the deciding variable, it is the amount of gas off-gassed into the blood from the tissues that is the deciding factor.

So, faster breathing will not speed up anything. What speeds up off-gassing is reducing the depth. However, at some point, you may speed up off-gassing to the point where bubbles form -- and you incur DCS. So, it's a fine line, with lots of physiology and physics involved. That's why I suggested Mark Powell's book.

Hope that helps --

 

[boulderjohn]

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I think the OP asked a pretty good question. I think the fact that there was recently a spirited debate on essentially the same topic in the Tek-to-Tek forum shows that it was not stupid and is undeserving of such mean-spirited derision.

 

[Cave Diver]

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[fnfalman]

If off-gassing is a worry at the safety stop, then stay longer at the safety stop. Do a 5-minutes or 6-minutes safety stop instead. No need to try to hyperventilate underwater.

 

[DevonDiver]

It is a good theoretical discussion.

But in practical terms, off-gassing can be improved by many other methods, without the drawbacks.