Fully exhale when diving? Breath control?

[rsingler]

The points made above about breathing more deeply are physiologically important. You normally have a modest volume of "dead space" that doesn't contribute to oxygen/CO2 exchange (pharynx, trachea, bronchi). When you are wearing scuba gear, there is additional dead space in your second stage.
Many divers trying to decrease their air consumption start "sipping" little breaths, trying to "not waste gas". This turns out to be the opposite of what should be done, because with small breaths, the fraction of the breath that is wasted on dead space is larger than with a bigger volume breath, where more of the breath gets down deep into the alveoli.

Scuba breathing, especially at depth, should be slow (avoid turbulent air flow with its increased resistance), somewhat deeper (to compensate for extra dead space without affecting buoyancy too much), and with a similarly increased exhalation (to dump CO2). In compensation, absent vigorous exercise, your breaths per minute will not be as frequent as at the surface. But once you have the technique down, you won't even think about it any more.

With that technique, plus streamlining and optimal weighting, you'll find your air consumption will improve markedly.

Dive safe!
Diving Doc

 

[TMHeimer]

Diving Doc, Thanks for the explanation of sipping and dead space. People have mentioned not to do it, but never exactly why not.

 

[bubblesmd]

This is a good exercise just in general, don't do it on scuba:



How (de-)tuned is your regulator? It is different: you have compressed air blown into you, but there's opening and closing pressure on the regulator that may be less than optimal for you.

It was a rental and I don’t think i have enough experience to tell the difference between a good or bad regulator.

I’m loving diving, so I’ll be getting my own regulator soon. Have the mask, snorkel, fins, and computer... next is the regulator!

 

[dmaziuk]

It was a rental and I don’t think i have enough experience to tell the difference between a good or bad regulator.

I’m loving diving, so I’ll be getting my own regulator soon. Have the mask, snorkel, fins, and computer... next is the regulator!

It's not good/bad: I like them detuned so they don't freeflow in my mouth and out the nose at the end of the inhale. My better half likes them to breathe easy, with much less "cracking" pressure. On some of them the adjustment knob is on the outside (not the same as the +/- aka dive/pre-dive lever).

I'd buy a BCD first. I did, anyway. If you can find a place to try out a back-inflate/backplate -- try it.

 

[Slow]

The points made above about breathing more deeply are physiologically important. You normally have a modest volume of "dead space" that doesn't contribute to oxygen/CO2 exchange (pharynx, trachea, bronchi). When you are wearing scuba gear, there is additional dead space in your second stage.
Many divers trying to decrease their air consumption start "sipping" little breaths, trying to "not waste gas". This turns out to be the opposite of what should be done, because with small breaths, the fraction of the breath that is wasted on dead space is larger than with a bigger volume breath, where more of the breath gets down deep into the alveoli.

Scuba breathing, especially at depth, should be slow (avoid turbulent air flow with its increased resistance), somewhat deeper (to compensate for extra dead space without affecting buoyancy too much), and with a similarly increased exhalation (to dump CO2). In compensation, absent vigorous exercise, your breaths per minute will not be as frequent as at the surface. But once you have the technique down, you won't even think about it any more.

With that technique, plus streamlining and optimal weighting, you'll find your air consumption will improve markedly.

Dive safe!
Diving Doc

I have generally had trouble with acid reflux while diving. On my last trip I was grumbling on the boat about how much it hurt even having taken antacid before the dive. A biologist was in our group and said she’d read research that lack of fully breathing out while diving could contribute to acid reflux.

I’ve always been a big air consumer (I blame it on 99th percentile lung capacity), but my consumption went down 10-20% AND all my acid issues went away the instant I started concentrating on fully breathing out.

I didn’t find it hard to control buoyancy either...It May help that I use very little weight.

 

[GreggS]

When I first started diving 5 years ago, my air consumption was atrocious, anywhere between .70-.90 sac rate. I am 6' tall and have weighed as much as 272 lbs but am now down to 245. I finally realized I was horribly over-weighted at 16 lbs of lead in fresh water (22 in salt water) wearing a 3mm full wetsuit with a 80 cf aluminum tank. I started reducing the amount of weight I was carrying and as I have reduced that weight, my sac rate came down. I'm now down to carrying 8 lbs of lead (14 in salt water) with the same configuration above and my sac rate is around .45. Once my wife got certified the year after I did, I had to slow down my finning so she could keep up with me. Didn't realize I was putting so much effort into it until then. That helped out as well.

Of course, as others have said, more experience will go a long way in reducing your air consumption. Get your weighting and trim right and the more you dive, the more comfortable you'll be in the water. With that, your breathing will stabilize and your air will last you longer. Just don't get distraught this early in your diving just because you're using up your tank of air quicker than someone else. It will come.

 

[wedivebc]

When I was learning to sing in choir, our leader had us practice breathing with our belly muscles rather than our chest. She also had us fully exhale slowly like you're holding a note for a long time. CO2 is what triggers breathing response and the more you can get rid of on each exhale the less air hunger you will feel when diving. This will extend your tank duration in amazing ways.

 

[BlueTrin]

This is a good exercise just in general, don't do it on scuba:



How (de-)tuned is your regulator? It is different: you have compressed air blown into you, but there's opening and closing pressure on the regulator that may be less than optimal for you.

How does this exercise transfer in lower air consumption ?

I think I can understand how it can help a free diver on a single breath but I am not sure how it transfer to scuba.

Is that because you are supposed to breathe using your diaphragm/belly like others said rather than your lungs in scuba ?

 

[Motoman4540]

As others have said, with 6 dives, you can expect poor air consumption. Big changes in depth, going up and down with each breath, is a good indication that you are overweighted. Carrying more weight also increases are consumption. Flailing and frequent finning also increase air use. You want to be as motionless as possible underwater, and your air use will automatically improve. Regarding breathing, I do a deeper inhale, and then slowly exhale in three or four short exhales, before taking another breath. I have found the doing this smoothly and relaxed, minimizes my air consumption. On a "regular" dive, i.e., starting at 70 or so feet and gradually making my way to 45 or 35 feet, when I first started, I struggled to get 40 minutes from a tank. Now, 400 dives later, I start at 80-90 ft. usually and spend a lot more time at depth (below 45 ft) and get at least 75 minutes from a tank, coming up with 500 psi. Just being relaxed will get you benefits!

 

[scubadada]

I have always had a relatively low gas consumption. It was many years before I paid attention to how I breathed. I take a relatively slow deep inspiration, have a short pause with glottis open, have a relatively slow exhale, and then immediately inhale again. I believe this maximizes CO2 elimination, oxygen loading is not a factor. You will notice that this is the opposite way that you breathe on land. After you get control of your buoyancy, trim, and propulsion, thinking about this might assist you. I would recommend that you follow your RMV, that will give you something objective to follow as you improve all of the variables.

Good diving, Craig