Air Integration & NDL Accuracy?

[CaveSloth]

When you dive without air integration, I would assume that NDLs are calculated based on an assumed constant breathing rate. When you have air integration, the computer can potentially know when you might be breathing more due to fighting a current, etc... Does the Teric take this into consideration and give a more accurate NDL or deco reading?

 

[runsongas]

gas consumption rate does not affect NDL, only depth/time/mix for the partial pressure

 

[CaveSloth]

gas consumption rate does not affect NDL, only depth/time/mix for the partial pressure

thinking

 

[CaveSloth]

So if I spend 10 minutes at 100 ft I absorb the same amount of nitrogen if I breathe X as if I breathe 10X?

 

[tbone1004]

So if I spend 10 minutes at 100 ft I absorb the same amount of nitrogen if I breathe X as if I breathe 10X?

correct. You care about inert gas absorption into the blood and then into the tissues. Your breathing rate doesn't change that. There are some scientific stuff published about it if you want to dig through the Rubicon foundations archives

 

[tursiops]

So if I spend 10 minutes at 100 ft I absorb the same amount of nitrogen if I breathe X as if I breathe 10X?

Yes. The N2 absorption rate is the limiting factor, not the amount of gas you are breathing.

 

[FreeFlyFreak]

So if I spend 10 minutes at 100 ft I absorb the same amount of nitrogen if I breathe X as if I breathe 10X?

I like the way you are thinking.
I have considered a similar thing.
Not just breathing rate, but body size/composition.

Analogy.
Drink more in the same amount of time get drunk quicker. However you don't exhale booze. It has time to be absorbed. The gas seems to be limited by lung transfer.
However, when looking at body size. Same amount of booze, same time, smaller body gets drunker.
But again, my GF is 28% less mass than me, and guess what, she breaths about 20-25% less gas.

So I guess it all averages out in the end.
But it is something I have been thinking about. You are not the only one.

 

[doctormike]

The likelihood of a clinical manifestation of decompression stress (i.e. DCS) is definitely dependent on a number of variables, including body type, workload, water temperature, hydration status, etc...

What the dive computer tracks is depth, time and mix. That's it. You can adjust the conservatism so that you will hit your NDL sooner or later in the dive, but the inputs to that algorithm are still depth, time and mix on all current dive computers to the best of my knowledge.

So that's why - even though there is a lot of individual variation in whether you get bent or not - dive computers don't take into account gas consumption. And as has been explained upthread, your N2 loading doesn't change if you are moving more gas through your lungs.

However, your risk of DCS for that amount of loading might well change if you are working harder. There simply isn't a computer that can (1) get that data accurately, and (2) apply it to the algorithm. So your question is certainly a reasonable one...

 

[Brian G]

Don't the Scubapro computers with heart rate monitor adjust the NDL based on the perceived exertion?

 

[doctormike]

So much for the best of my knowledge!