Guys,
How did we learn to breathe on scuba from our Instructor in Open Water I? Breathe, "naturally", he/she said, or something similar. To many divers, that means, "I don't have to pay attention to how I breathe, I just breathe like my body tells me to, naturally." However, I am pretty sure that was not the intent? Naturally, kind of means, meeting the diver's biological needs.
When I talk about diaphragmatic breathing, I am talking about a technique using the diaphragm to fully ventilate the lungs, especially the lower lobes, like practitioners of Hapkido or Yoga. It is essentially a slow sigh. Using the muscles of the chest will inflate the upper lobes of the lungs, but does not do much for the lower lobes, so essentially, you are getting less ventilation, for the invested work of breathing (WOB). You get more O2, and get rid of more CO2, with a diaphragmatic breath, than with a shallow chest breath, because of things like anatomical dead space and ventilation.
However, none of us needs to walk around using deep, slow, diaphragmatic breathes all day long!! Personally, for me, I will take no more than 6 full diaphragmatic breathes at a time when I feel the need for them. When might I need them, you ask???
How about when I am sitting on the bench, all ready to jump in the water, and there is a problem with the boat, my buddies gear, or some other delay??? I am hot, my gear is heavy, and who is not going to be stressed out in that situation? So, I close my eyes and take a few deep breathes. Load some O2, get rid of some CO2, and try not to start the dive too stressed.
How about when the sea conditions are a little sporty? I will stop once I am on the wreck, and out of the current, to check on my gas, my gear, and my breathing. I will try to use my hands, and arms, just like some of you have described, to pull myself along the anchor line, or the wreck, and conserve energy, whenever I can. The small muscles of the arms will make much, much less CO2 than fining, and I assume anyone who has had to fight a current with fins will agree.
I also use a few diaphragmatic breathes, anytime I am facing stress during the dive. Stress can drive up the respiratory rate and promote shallow breathing. When the Bull Shark wants my fish, I take a few Don Jon breathes. It also makes the shark think I am not panicked prey, but a Hapkido Warrior!
Anytime I am physically or psychologically challenged, I will try to take a couple of slow, deep, abdominal breathes.
I am not sure if utilizing diaphragmatic breathing will enable Richard to run up more dive time or not?? However if he is more economical with his expenditure of energy, stays relaxed, and ventilates well, he will probably make more efficient use of his gas supply, and I guess that could lead to more bottom time, and/or safer ascents, as far as dealing with the threat of DCS? Besides, he might just feel better as well?
IMHO, all divers, not just deep divers, need to pay attention to how they might be exerting themselves in the water, as well as to how they are their breathing. The adjustments we make are more art, and less technical.
Cheers
JC