Narcosis Oxygen and mixed gases

Question:
When skip breathing (or fast breathing) do you influence your non decompression limit and why ? (OK, skip breathing is dangerous because of CO2 intoxication and risk of A.G.E.).

Answer:
Generally speaking, skip breathing or deep continuous breathing do not influence inert gas uptake, as it depends on the partial pressure gradients between the alveolar gas and the tissues. The fact that the alveolar gas is moving or not - for the time intervals involved in skip breathing or deep continuous breathing - is negligible to this respect. A theoretical issue may involve that the possible and relative increase in CO2 retention involved in skip breathing ( but it should be way more than skip breathing and almost breath-holding) may produce a certain vasodilation and a potential increase in inert gas uptake. But this lacks any scientific evidence, so far.

Question:
Are there tables of the toxicity of oxygen in function of time and partial pressure (for an average person) ?

Answer:
Yes of course, both with regard to Pulmonary and to Neurological Oxygen Toxicity. The reference studies are those of Clark and Lambertsen. You can find very useful information on this subject in the book "Oxygen and the Diver", by K. Donald, which you can order at DAN Europe.

Question:
How does a human body react on a non natural gas mixture (like a He/O2/N2 mixture)?

Answer:

 

The main effects are the following:

 

difference in gas density, which affects positively the work of breathing the maximal voluntary ventilation potential and the maximal perfomance at depth, High Pressure Nervous Syndrome, depending on speed of compression and correctable with the addition of N2 Thermal loss due to breathing helium.

 

You can find useful information on the book "The physiology and medicine of diving" by P.Bennett and D.Elliott, which you can also find at DAN Europe.