Nitrogen absorption, and tissue "compartments"

[boulderjohn]

Thanks for the reply. Of course, when one question is answered, new questions arise: Someone suggested to me, that a fast descent would increase bottom time, the idea being that fewer respiration on descent = less time for Nitrogen to be absorbed into the body while descending. Taking into consideration 1/2 time for Nitrogen absorption, would there be any validity to this argument? Besides my question, are there any known benefits from a quick descent vs slow descent?

As awap said, the breathing rate doesn't matter, since the N2 level in the lungs won't change much during each breath, and that is what counts. On the other hand, if your dive plan calls for 15 minutes exploring a deep site, since time on descent is counted as bottom time on the tables, the less time you spend descending the more of that 15 minutes you will have at your destination.

 

[mathauck0814]

Thanks for the reply. Of course, when one question is answered, new questions arise: Someone suggested to me, that a fast descent would increase bottom time, the idea being that fewer respiration on descent = less time for Nitrogen to be absorbed into the body while descending. Taking into consideration 1/2 time for Nitrogen absorption, would there be any validity to this argument? Besides my question, are there any known benefits from a quick descent vs slow descent?

Rapid descents are theorized to contribute to the effects of narcosis, however.

 

[NAM001]

nitrogen density should be a function of depth compressing the gas and not the breathing rate. like how many molocules per cu in. i would think of it like partial presure of a gas. the denser the gas the higher rate of absorbsion in the tissue's till it equalizes.

 

[debajo agua]

Does anyone have any first hand experience with narcosis and a rapid descent?

 

[boulderjohn]

Narcosis is very unpredictable, and it would be hard to say the degree to which descents factored in. The theory is that the carbon dioxide your body creates through the effort of a fast descent contributes its own narcosis. (Nitrogen is not the only narcotic gas.) I think that if you just drop down as fast as you can without working, it should not be a factor. I will also say that I have done a number of very hard working descents without noticing anything different in terms of narcosis. For example, if you are dive bombing a wreck, you may have to work very hard all the way down to depths even beyond 200 feet. (Dive bombing is when the captain takes a guess as to how fast the current is going, assumes you are going to descend very fast, and then drops you off at a spot where he hopes you will hit the wreck with that fast descent.)