Im not sure if someone can provide some insight into NDL's for me, as I noticed on a recent dive that NDL's simply calculate from depth and the minutes/ seconds spent at that depth, with no account for the gas use within that timeframe, so if someone uses for example 200bar on a single 10 and someone else only uses 50bar from a single 10 (exact same profile) the first would have absorbed a lot more nitrogen, so would have an increased risk of a DCI no?
question about NDL's, need some insight..
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Inert gas uptake is a function of nitrogen coming into the tissues. It diffuses pretty consistently regardless of respiratory rate because it is a pressure differential across the membrane. Your blood is what matters not your lungs.
Movement of gas into the tissues is not a function of respiratory rate, it is a function of the difference between the partial pressures.
As you descend, the partial pressure of the gases you're breathing goes up. As it goes up, the gases move into the tissues faster, until the partial pressure of the gas in the tissue is equal to that of the gas you're breathing. At this point, the tissue is "saturated".
The deeper you dive, the faster the tissues will become saturated, resulting in shorter NDL times.
When you ascend, the partial pressure of the gases you're breathing goes down, causing gas to move back out of the tissues until, again, the partial pressures match. This is "off gassing". If you ascend too quickly, the gases moving out of the tissues form bubbles. This is being bent.
The rate at which you breath has no real impact on these pressures, and therefore no impact on tissue saturation.
As you descend, the partial pressure of the gases you're breathing goes up. As it goes up, the gases move into the tissues faster, until the partial pressure of the gas in the tissue is equal to that of the gas you're breathing. At this point, the tissue is "saturated".
The deeper you dive, the faster the tissues will become saturated, resulting in shorter NDL times.
When you ascend, the partial pressure of the gases you're breathing goes down, causing gas to move back out of the tissues until, again, the partial pressures match. This is "off gassing". If you ascend too quickly, the gases moving out of the tissues form bubbles. This is being bent.
The rate at which you breath has no real impact on these pressures, and therefore no impact on tissue saturation.
JanWerbinski
New
All above answers are wrong.
SAC is related to stress, workload, thermal stress etc. Why do you have higher SAC?
Let's take workload. It is DCS risk factor. More workload is more inert gas intake. Same with cold.
But I wouldn't worry. NDL for rec divers is set with big margin error and it's very unlikely you will be sick just because of higher air usage.
Here is the proof:
Workload | Decompression Sickness - DAN Health Issues & Diving
Thermal Stress | Decompression Sickness - DAN Health Issues & Diving
SAC is related to stress, workload, thermal stress etc. Why do you have higher SAC?
Let's take workload. It is DCS risk factor. More workload is more inert gas intake. Same with cold.
But I wouldn't worry. NDL for rec divers is set with big margin error and it's very unlikely you will be sick just because of higher air usage.
Here is the proof:
Workload | Decompression Sickness - DAN Health Issues & Diving
Thermal Stress | Decompression Sickness - DAN Health Issues & Diving
R
redacted
Guest
So, does that mean that men must be more stressed than women since they tend to have a higher SAC??
Perhaps there are other independent variables involved.
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So, does that mean that men must be more stressed than women since they tend to have a higher SAC??
Perhaps there are other independent variables involved.
Yes, perhaps. And perhaps that was mentioned...
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SAC is not directly tied to workload or thermal stress. Most divers have a higher SAC when it is cold, but inert gas transfer is decreased when you are cold. With workload, you can be in poor physical condition, have a very low resting SAC rate, and have an incredibly high sac due to perceived workload, but in actuality your muscles aren't working that hard. You could also be a marathon runner and while your resting SAC rate is normally higher than someone in poor physical condition, exerting the same workload won't increase your SAC rate significantly even though your muscles are working much harder than they are at rest.
Workload and thermal stress need to be factored into your conservatism, but SAC rate should not be factored in.
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