air utilization

[rawls]

I just posted a question in the basic SCUBA discussions forum about my using alot of air on dives. I guess I should have posted it here. So I guess I will post it here too. Forgive me because I am new to this site. I use 100 cubic centimeter tanks and I usually breathe them down before my ndl is up. This happens generally in the 60 to 70 foot range. I don't have the problem at shallower depths and I know that has to do with lesser pressure. I don't have the problem at deeper depths because I reach my ndl before I use the tank. I am not anxious. I don't think it is a CO2 problem because I have never had any s/s of CO2 retention such as headaches. I have never had any adverse problems after a dive. This happens not when I am exerting myself. It happens when I am doing a relaxing dive. My Dr looked at my x-ray on a recent physical and he said I have "big" lungs. I guess he meant I have room for a large vital capacity. I haven't looked at surface and depth consumption rates. Could it just be my physiology or is there something I can do about it. I just want to surface from a 65 foot dive because I am reaching my ndl instead of the bottom of my tank.

 

[TSandM]

The number of liters of air you have to move through your lungs in a minute is dependent upon your production of carbon dioxide. This is related to your metabolic rate and activity level. In addition, anxiety can cause you to overbreathe, and an inefficient breathing pattern (eg. frequent shallow breaths) can cause you to ventilate your lungs inefficiently and waste air.

Relaxing under water, so that you don't breathe from anxiety, helps a lot, and this is a large part of the reason new divers use more air than experienced people. Learning not to motor along also helps -- diving is best done slowly. Getting into correct trim helps, because if you are not horizontal, you are pushing a great deal more water out of the way than you need to, and that takes muscle which takes air. Becoming fit, so that you need to use less muscle mass to accomplish the same task, also reduces your CO2 production and therefore your respiratory rate.

"Big lungs" has nothing to do with it, unless you are showing hyperexpansion due to chronic pulmonary disease (from long term smoking, for example) which could affect the efficiency of gas transfer in your lungs and raise your air needs. But most people with COPD that bad wouldn't even try to dive.

 

[Dive-aholic]

My tidal volume is slightly more than my wife's, so my air consumption is slightly more than hers. It is all a part of physics. But there are times she breathes more than me (cold water).

I'm not sure what your doctor meant by "big lungs". Most paople will breathe in the 550 to 750 tidal volume range, depending on body size (going back to me v. my wife). But breathing down a 100 is just newness. Your air consumption will decrease the more you dive. Don't worry about working at it because that will probably just increase the consumption. Just dive and have fun. When you hit 50 and 75 dives, go through your log and determine your rmv on similar dives. You should see a good difference.

 

[DandyDon]

I'm curious here...

I use 100 cubic centimeter tanks and I usually breathe them down before my ndl is up.

Okay, I know this is a typo, as 100 CCs is only 1/10 of Liter...?? You don't list your location on your Profile, so - who knows?

My guess is that you meant 100 cubic foot tanks. If so, no biggie - your air consumption will get better with more diving. :05:

 

[rixemailfl]

When I first started diving I was using tons of air.

Went on a trip to the Bahamas where I dove every day for several days straight & started watching myself as far as my breathing goes.

I figured out that with all my years of singing (since I was a little kid) that I tend to always take a full breath of air every time I breathe.

This also was playing a slight bit of havoc with my buoyancy.

Now I tend to control the depth of my breathing & I don't use quite as much as before.

Keep practicing...:14:

 

[Kevfin]

Here's a neat tool to figure out your SAC (Surface Air Consumption). As you dive more, become more relaxed, and fine tune your gear, you should be able to reduce the number...

SAC calculator (bottom of the page)
http://www.spearfishing.org/bruces_tips/java/sac.html