Air Consumption and DCS -- Any Connection?

[ChameleonAmy]

So, I was thinking...... If a diver has a greater air consumption than others, does that put them at a higher risk for DCS? After all, increased air consumption means they're taking in additional nitrogen that the body must deal with. But, with every inhalation also comes an exhalation that gets rid of some of that added nitrogen. Any thoughts on this, oh experienced divers?

 

[BigJetDriver]

Well, actually there is no correlation between the rate of breathing and the rate of on-gassing. The relationship is between partial pressure of the inert gas and the time the diver is exposed to it.

Your position in the water column determines the ambient pressure, and that pressure causes your regulator to equalize the pressure as it provides gas to your lungs.

If you remember your Henry's Law, the amount of gas going into a solution (in this case you) is DIRECTLY proportional to the pressure of that gas ON the solution.

That pressure, and the amount of time you are exposed to it determines the amount of nitrogen (the inert gas of choice for most recreational divers) you get in you. This why you see different TIME LIMITS at different depths on your tables. It is the time limits that keep you from having to do decompression stops, hence the name: "No Decompression Limit (NDL) Tables."

 

[Red Sea Shadow]

Amy,
Actually the opposite could be true is some cases.
If you are excellent on air, i.e., you consume much less air than normal, you could do some extended-time dives thus be exposed to DCS.

 

[John C. Ratliff]

Both Dead_Sea_Shadow and BigJetDriver have it right. It is the time at depth that makes a difference, and not breathing rate. This has to do with how nitrogen is absorbed into the blood stream, and not how much you breath. Remember that the nitrogen stays in about the same concentration in the lungs no matter whether there is lots of oxygen or a little less through respiration (CO2 replaces the O2 used). The driving force is the partial pressure difference between the lungs air spaces and the blood. The greater that difference, the more nitrogen goes into solution into the liquid part of the blood stream. So don't worry about air consumption, worry about time and depth, and watch very closely that you don't get into a decompression situation. This means staying well within the no-decompression limits of the tables or your computer.

SeaRat

 

[Red Sea Shadow]

Both Dead_Sea_Shadow and BigJetDriver have it right.

OK John. Red Sea Shadow not Dead Sea. The Dead Sea is totally different.

 

[MoonWrasse]

So, I was thinking...... If a diver has a greater air consumption than others, does that put them at a higher risk for DCS? After all, increased air consumption means they're taking in additional nitrogen that the body must deal with. But, with every inhalation also comes an exhalation that gets rid of some of that added nitrogen. Any thoughts on this, oh experienced divers?

Air consumption doesn't necessarily mean they are using it - just sucking it in and blowing it out quickly will consume lots of air. In fact they might have a lower chance of a DCS hit as their dive might be air limited (instead of NDL limited).

Also someone who's got low consumption, but is shallow breathing or skip breathing might be building up CO2, which I've heard might increase your odds of getting DCS.

 

[BigJetDriver]

Also someone who's got low consumption, but is shallow breathing or skip breathing might be building up CO2, which I've heard might increase your odds of getting DCS.

Actually you are correct, quite a few decompression researchers have posited that increased pCO2 does increase the chance of DCS in any situation, as well as the recognized increase in possible oxygen toxicity.

 

[Red Sea Shadow]

Also someone who's got low consumption, but is shallow breathing or skip breathing might be building up CO2, which I've heard might increase your odds of getting DCS.

I think there's some sort of conflict here. Normally, shallow breathing does not match with low air consumption. Short shallow breaths leave more than 85 to 90 percent of your lungs filled with carbon dioxide-rich “dead air.” All that carbon dioxide itches to get out, so you're forced to take another breath before you actually need the oxygen. You draw air you don't need from your tank, cycle it through the top half of your respiratory system just to pick up the carbon dioxide most urgent to escape, and dump it into the blue.

 

[Chad Carney]

Agreed, no direct correlation between high breathing rates and DCS.

Usually easy breathers are not shallow breathers, and have good skills and habits all around.

Whereas the gas hogs I have known are often out of shape, have poor buoyancy control & bad trim, poorly matched fins, high drag gear, and possibly poor breathing regulators. These characteristics can cause more arduous dives, and more CO2 production. Therefore they could indirectly be more likely to produce a DCS problem.

RSS, I didn't see your post above, I think the clocks are off... but we agree shallow breathing won't get you low consumption!

JMHO,

Chad

 

[dumpsterDiver]

What he said........If the higher gas consumption is tied to a higher workload underwater, being cold or being in poor physical condition, then yes a person who sucks up a lot more air may be more likely to get bent!