On the likelihood of decompression sickness during H2 biochemical decompression in pigs

Abstract

A probabilistic model was used to predict decompression sickness (DCS) outcome in pigs during exposures to hyperbaric H2 to quantify the effects of H2 biochemical decompression, a process in which metabolism of H2 by intestinal microbes facilitates decompression. The data set included 109 exposures to 22–26 atm, ca. 88% H2, 9% He, 2% O2, 1% N2, for 0.5–24 h. Single exponential kinetics described the tissue partial pressures (Ptis) of H2 and He at time t: Ptis = ∫ (Pamb − Ptis) · τ−1d t, where Pamb is ambient pressure and τ is a time constant. The probability of DCS [ P(DCS)] was predicted from the risk function: P(DCS) = 1 − e − r , where r = ∫ (Ptis h 2 + Ptis he − Thr − Pamb) · Pamb−1 d t, and Thr is a threshold parameter. Inclusion of a parameter ( A) to estimate the effect of H2 metabolism on P(DCS): Ptis h 2 = ∫ (Pamb − A − Ptis h 2 ) · τ−1d t, significantly improved the prediction of P(DCS). Thus lower P(DCS) was predicted by microbial H2 metabolism during H2 biochemical decompression.