Breathing Rate in Computer Calculations?

[RobPNW]

Clearly as you go deeper, your gas consumption rate increases with gas pressure, which accelerates the accumulation of N2 in your body. I get that basic physics and physiology. Does anyone know if computer algorithms account for actual breathing rate? And true air consumption rate?

As an example, let's say you're diving at 10m and then you go to 30m and you're breathing rate and effort are identical at each depth. One can expect the air consumption rate to be double at 30m that it is at 10m.

But what if you're working at 30m or excited, and your breathing rate is 50% faster at 30m? That would put your actual air consumption at around triple what it would be at 10m. And accumulation of N2 would be proportionally higher as well.

So do computers, and I guess more accurately air integrated computers, use the actual air consumption rate in it's NDL calculations, or does it just keep track of how long the diver is at any depth?

Thanks in advance,
Rob

 

[scubadada]

Nitrogen uptake is independent of your breathing rate. It is dependent on depth.

 

[RobPNW]

I guess I was thinking more in terms of a non inert gas like O2 which would be absorbed more and used in cellular processes versus N2. Thanks.

 

[Centrals]

Consumption rate is very important but for different reason: faster the rate means shorter the diving time. It has nothing to do with NDL.

 

[Divectionist]

As above, but regarding AI computers:

Air consumption at depth is converted to surface air consumption so you have a value independent of depth to keep track of. A computer would show you constantly averaged SAC value over the last couple minutes or so, meaning that if you know your SAC is, say 1.0 (with a given tank volume etc) then you can monitor your breathing rate and immediately see that you are stressed if it climbs up to 1.5 for example, or extra smooth if it dips under your usual value. Just note that SAC changes when you change tank volumes as the given pressure corresponds to a different volume of gas.

The biggest benefit in my view is the gas time remaining calculation, giving you your GTR at any given depth and pressure based on your current SAC rate. That one is a gem, especially if you run out of air before touching your NDL on shallower dives. Just make sure you understand what reserve pressure your computer bases this on. For example, if you set it to show GTR leading to 50bar at the surface, you may want to jack the reserve up to allow for your consumption at the safety stop, and perhaps a little extra margin, that way your GTR will actually be ascent incl. stop, which makes it a bit softer of a limit to dive to.

 

[Hatul]

The only computers that take into account the workload either from breathing or from heart rates are the Galileos and the G2. I don't believe any other dive computers take these into account in the algorithm.

 

[scubadada]

The only computers that take into account the workload either from breathing or from heart rates are the Galileos and the G2. I don't believe any other dive computers take these into account in the algorithm.

And nobody knows how these work

 

[Angelo Farina]

And nobody knows how these work

Well, this is not entirely true. These Scubapro-Uwatec computers are claimed to work following Buhlmann ZHL-16 ADT DD.
See their manual, here, at page 2: https://www.scubapro.com/sites/scubapro_site/files/trimix_user_manual-eng.pdf
That is the "adaptive" version of the classic Bulhmann algorithm, which accounts for workload, and is well documented in the scientific literature.
Of course no one knows the actual details of the computer code embedded in these devices, but the same can be said for any other diving computer...

 

[Angelo Farina]

Nitrogen uptake is independent of your breathing rate. It is dependent on depth.

Well, this is something I do not think is entirely true. Workload has a significant effect on Nitrogen migration between different tissues, and a number of "undeserved" DCS occurred to divers who over-exerted during their dive.
Air consumption can be used as a "proxy" for workload, together possibly with other parameters, such as heart rate.
Personally, when diving with US Navy tables, I always followed the rule to consider a table for a longer dive time whenever I perceived to have done some abnormal effort, for example swimming against current, etc.

 

[boulderjohn]

As was established in a number of past discussions, heart rate is a factor when it increases or decreases blood flow (perfusion) to and from tissues. While increased breathing rate may well be associated with increased perfusion, it is in itself not a factor in nitrogen on-gassing or off-gassing.

Many decompression divers have started doing mild exercise during their last deco stops rather than hang in place motionless in order to increase perfusion and off-gassing. I do a lot of deco diving in a large sinkhole, and we all casually and quietly swim around the lake the lake during our last 2 deco stops, hopefully maintaining blood flow while simultaneously maintaining a slow breathing rate.

I am not aware of any studies that define the effect of changes in perfusion enough to become a measurable factor in diving, despite what the computers that measure heart rate say.