Breathing

[RJP]

At the Minuit I'm just galloping air down and I'm sure I'm breathing incorrectly

You don't indicate whether you're "gulping down air" because you NEED more air or simply employing that as your breathing style.

Here's a post I put up the other day regarding the related topics of breathing technique and air consumption:

Anything and everything you need to know to improve air consumption comes back to two key things from a physiology standpoint:

1.) Air (O₂) consumption is a DEMAND function
2.) Air (O₂) is consumed in your body's muscle cells, not your lungs

Accordingly the most effective way to reduce your O₂ consumption is to reduce the DEMAND that the muscle cells in your body have for O₂. There are 13 key "Demand Reduction Strategies" that any and every diver can employ to improve their O₂ consumption:

1. Slow down
2. Get more comfortable in the water
3. Slow down
4. Get your weighting fine-tuned
5. Slow down
6. Get your horizontal trim dialed-in
7. Slow down some more
8. Stop swimming with your hands and arms
9. Slow down even more
10. Utilize efficient kick styles
11. Just a little bit slower... please?
12. Streamline your gear
13. Slow down - you're still moving too fast!

OK, now that we've addressed the best ways to improve your air consumption rate, let's talk a little bit about how a diver should breathe...

There is much advice here on SB about reducing your air consumption by controlling/modifying/focusing on your breathing rate. I won't add anything to those points, other than to say that an awful lot of that advice is largely inaccurate. Let's use a car analogy:

Muscle cells (where O₂ is burned) = cylinders (where gas is burned)
Circulatory system (delivers O₂ to muscle cells) = fuel injectors (deliver gas to cylinders)
Lungs (delivers O₂ to the circulatory system) = gas tank (delivers gas to fuel injectors)
Regulator (delivers O₂ to the lungs) = Pump at gas station (delivers gas to car's gas tank)
Scuba tank (where reg gets O₂ from) = Storage tanks at gas station (where pump gets gas from)

Suggesting that you can meaningfully improve your air consumption by controlling how often, how much, and how slowly you put air into your lungs is like suggesting that you can improve your car's gas mileage by reducing the number of times you purchase gas, always filling and emptying the tank completely, and pumping the gas into your tank slowly. Those are all SUPPLY strategies... but remember, O₂ consumption is a DEMAND function. (Note - for simplicity of this post, I'm not addressing the "exhaust" portion of the equation, since the question was about "consumption.")

Now, before anyone bites my head off, I'm not saying that things like breathing rate, speed, and depth are absolutely unimportant. I'm merely point out the fact that - just like our car analogy - assuming we don't try to deliver more or less O₂/fuel to our muscle cells/cylinders than they DEMAND everything will be fine. Sure, if we don't deliver enough - or deliver too much - O₂/fuel our "engine" will run rough and waste some fuel. But if our lung/gas tank function is within a normal range... our body/car will run fine and we don't need to worry about these things.

Accordingly, I will politely disagree with people who say "focus on your breathing at all times" or those who will offer advice about how many seconds to inhale and how many seconds to exhale and the like. My advice on breathing rate, depth, etc is as follows:

1. Breathe normally
2. If there is a problem causing you to breathe abnormally, fix the problem
3. Breathe normally
4. STOP focusing on how you're breathing!
5. Breathe normally
6. Ensure that the 13 "Demand Reduction Strategies" listed at the top of this post are second nature, so you can STOP focusing on those things too! (Plus, reducing your body's demand for O₂ will help ensure that you are breathing normally!)
7. Focus on your dive - that's why you're underwater

Best regards - Ray

Ray Purkis

 

[daniel1948]

I think the engine analogy is an oversimplification because a lot of new divers breathe so fast that too little of the oxygen in the tank gets into the bloodstream, being instead exhaled before it gets absorbed. Obviously, slowing down and improving efficiency of movement is essential, but breathing slowly is in itself a relaxation strategy. And breathing deeply allows more of the oxygen to be absorbed, and allows more CO2 to be expelled. Since the urge to breathe is driven by CO2 in the blood, expelling more of it (by breathing deeply) helps reduce the urge to breathe faster.

 

[dumpsterDiver]

I think the engine analogy is an oversimplification because a lot of new divers breathe so fast that too little of the oxygen in the tank gets into the bloodstream, being instead exhaled before it gets absorbed. Obviously, slowing down and improving efficiency of movement is essential, but breathing slowly is in itself a relaxation strategy. And breathing deeply allows more of the oxygen to be absorbed, and allows more CO2 to be expelled. Since the urge to breathe is driven by CO2 in the blood, expelling more of it (by breathing deeply) helps reduce the urge to breathe faster.

I agree. The real challenge is to manage carbon dioxide not intake of oxygen since the partial pressure of oxygen is much higher at depth than at the surface. So issues like full exhalation (or more full anyway) improve the efficiency of CO2 removal are critical to efficient use of the gas and feeling comfortable.

Breathing normally is NOT what I recommend. As others have said, deeper and slower than normal work better underwater because it helps eliminate CO2, tends to calm the diver (certainly more than panting) and I think helps to ameliorate the issues with work of breathing the more dense gas at depth.

Counting and timing my breaths never worked for me, but slower and deeper helps me.

 

[RJP]

I think the engine analogy is an oversimplification

Analogies are oversimplifications by definition.

because a lot of new divers breathe so fast that too little of the oxygen in the tank gets into the bloodstream, being instead exhaled before it gets absorbed.

Huh?

Assuming you are breathing uncontaminated air - and unless your lungs have completely collapsed - oxygen is absorbed throughout the entire ventilation cycle because your lungs ALWAYS have some volume of air/gas in them. This residual volume (RV) is between 1000-1500mL for an adult male. As long as there is air in the lungs, the lungs are absorbing oxygen.

Plus, consider the human body's respiratory response to exercise. Run a 100yd dash and think about why you are breathing FASTER rather than slower. Pulmonary ventilation rate increases in direct proportion to the intensity and metabolic needs of the exercise - your body needs more oxygen in and needs to get rid of more CO2. Obviously increased ventilation rate does not impair oxygen absorption.

Since the urge to breathe is driven by CO2 in the blood, expelling more of it (by breathing deeply) helps reduce the urge to breathe faster.

Other than hyperventilating, you cannot "expel more" CO2 than the rate at which your body produces it and sends it to the lungs. (PS - the alveoli in the lungs is where CO2 triggers the urge to breathe, not the blood.) This is why the most effective way to reduce the urge to breathe... is to reduce the body's production of CO2... by reducing the metabolic processes associated with exertion.

I'm not discounting the benefits of breathing slowly and deeply, simply pointing out that - as mentioned above - this is a predominantly a DEMAND function. Reduce the metabolic demand on your body (receiving O2 and removing CO2) and you reduce your breathing rate.

 

[dumpsterDiver]

Analogies are oversimplifications by definition.



Huh?

Assuming you are breathing uncontaminated air - and unless your lungs have completely collapsed - oxygen is absorbed throughout the entire ventilation cycle because your lungs ALWAYS have some volume of air/gas in them. This residual volume (RV) is between 1000-1500mL for an adult male. As long as there is air in the lungs, the lungs are absorbing oxygen.

Plus, consider the human body's respiratory response to exercise. Run a 100yd dash and think about why you are breathing FASTER rather than slower. Pulmonary ventilation rate increases in direct proportion to the intensity and metabolic needs of the exercise - your body needs more oxygen in and needs to get rid of more CO2. Obviously increased ventilation rate does not impair oxygen absorption.





Other than hyperventilating, you cannot "expel more" CO2 than the rate at which your body produces it and sends it to the lungs.

However, you CAN retain CO2 and have it build up if you use an inefficient or inadequate means of breathing. Also some people tolerate higher CO2 levels and have a diminished response to it.. This is probably not good for scuba divers and highly desirable and even strived for by freedivers.

 

[RJP]

[/B]However, you CAN retain CO2 and have it build up if you use an inefficient or inadequate means of breathing. Also some people tolerate higher CO2 levels and have a diminished response to it.. This is probably not good for scuba divers and highly desirable and even strived for by freedivers.

Yup. If you are doing something wrong which results in inadequate ventilation/gas exchange... by all means FIX it.

 

[dumpsterDiver]

Analogies are oversimplifications by definition.



Huh?

Assuming you are breathing uncontaminated air - and unless your lungs have completely collapsed - oxygen is absorbed throughout the entire ventilation cycle because your lungs ALWAYS have some volume of air/gas in them. This residual volume (RV) is between 1000-1500mL for an adult male. As long as there is air in the lungs, the lungs are absorbing oxygen.

Plus, consider the human body's respiratory response to exercise. Run a 100yd dash and think about why you are breathing FASTER rather than slower. Pulmonary ventilation rate increases in direct proportion to the intensity and metabolic needs of the exercise - your body needs more oxygen in and needs to get rid of more CO2. Obviously increased ventilation rate does not impair oxygen absorption.





Other than hyperventilating, you cannot "expel more" CO2 than the rate at which your body produces it and sends it to the lungs. (PS - the alveoli in the lungs is where CO2 triggers the urge to breathe, not the blood.) This is why the most effective way to reduce the urge to breathe... is to reduce the body's production of CO2... by reducing the metabolic processes associated with exertion.

I'm not discounting the benefits of breathing slowly and deeply, simply pointing out that - as mentioned above - this is a predominantly a DEMAND function. Reduce the metabolic demand on your body (receiving O2 and removing CO2) and you reduce your breathing rate.

I didn't know the aveoli had sensors and were the source of the feeling that you need to breath?

 

[RJP]

I didn't know the aveoli had sensors and were the source of the feeling that you need to breath?

Yeah - brain fart. I jumped a step or two from changing partial pressure in alveoli to Ph change in blood to medulla oblongata, etc

 

[eelnoraa]

I am with PfcAJ. Breath normally like how you do it on land, which should be quite slow and effortless. Not deeper or shallower, just breath naturally.

A lot of people become anxious and breath shallower, this not only affect your SAC but also affect your buoyancy. If you force yourself breath slower/deeper than how you are naturally doing it, once task loaded, you breather pattern will change and affect buoyance as well. The key here is natually and consistantly, worry about SAC later. Once you become comfortable, your SAC will drop

 

[daniel1948]

Assuming you are breathing uncontaminated air - and unless your lungs have completely collapsed - oxygen is absorbed throughout the entire ventilation cycle because your lungs ALWAYS have some volume of air/gas in them. This residual volume (RV) is between 1000-1500mL for an adult male. As long as there is air in the lungs, the lungs are absorbing oxygen.

Breathing deeply circulates the air all the way down into the lungs, exposing more of the lung surface to the air and increasing the efficiency of gas exchange. Breathing shallowly allows air to stagnate at the bottom of the lungs, reducing the efficiency of gas exchange.

And although gas exchange is always happening as long as you are breathing, the faster you breathe the faster you will expend the air in your tank. The OP, like all of us, is concerned with making that tank of air last as long as possible. You can reduce your O2 demand to the bare minimum, but if you breathe fast, your tank will empty out sooner.

As DumpsterDiver points out, the elevated PO2 at depth means that there's plenty of oxygen available. What we're concerned about is production and expulsion of CO2. We're all agreed that efficiency of movement is critical because that relates to CO2 production. Breathing deeply increases the efficiency of CO2 expulsion, and breathing slowly avoids expending your tank gas faster than needed.

Deep and slow expels the most CO2 with the least use of tank gas.

This of course applies to open-circuit gear. I have no experience with closed-circuit gear and have never given it much thought. I saw some guys preparing rebreathers for a dive once, and the complexity of the gear scared me. Sorry, that was off topic.