Theoretical evaluation of safety of dives completed by non-stop ascent to surface

Our model of decompression sickness determines the cumulative probability of developing symptoms of this illness by the exponential equation whose index is the integral cumulative risk function of all body tissue lesions by bubbles, Fcum(t) = ΣFn(t). The underwater dives may be considered as practically safe in the context of this model when the function Fcum(t) during its growth will not exceed some small value Fcum-max = ΣFn-max. Using hypothetical values of parameters of tissues and functions Fn(t), we calculated the curves depth-duration for practically safe non-stop dives with air and with mixtures of oxygen with helium, neon and argon. Doing so, we obtained the distributions of values Fn-max in regard to the values of inert gas washout half-times from tissues which show that the tissues experienced the largest risks of bubble lesions are different for dives with different duration. The comparison of the indicated curves shows that the short-term dives with air are less dangerous and the long-term dives are more dangerous than the dives with helium-oxygen mixture. At the same time, the least risk of bubble lesions of tissues arises at dives with neon-oxygen mixture and the greatest risk arises at dives with argon-oxygen mixture. © 2010 Pleiades Publishing, Ltd.