Venous Gas Emboli in Goats After Simulated Submarine Escape from 290 msw Breathing Air or Hyperoxic Gas

Abstract

Escape from a disabled submarine has many inherent risks including the development of venous gas emboli (VGE). Breathing hyperoxic gas during rapid ascent from 2500 kPa (240 msw) reduces VGE; we investigated whether it would also be beneficial during an escape from 3000 kPa (290 msw), thought to be at the limit of human escape from a sunk sub. Adult castrated male or female goats (45-85 kg; N=35) underwent dry chamber compression to 3000 kPa in 28 s, then decompressed at a rate of 2.75 m x s(-1) while breathing either air or hyperoxic gas (60/40% O2/N2). Postsurfacing, precordial Doppler measurements were made using the Kisman Masurel (KM) scoring system; the animals were observed for signs of decompression illness (DCI) and/or oxygen toxicity. Six animals in the air group (N=19) and two in the hyperoxic group (N=10) suffered from severe pulmonary barotrauma on surfacing and were euthanized. No cases of DCI arose later than 5 min postsurfacing. Oxygen toxicity was not observed. Although initial bubble scores (median KM score 4) were the same in both groups, the time taken for the median KM score to reach 3 or less was significantly faster in the hyperoxic group (20 min vs. 120 min). Disappearance of VGE was faster in the hyperoxic group. Breathing hyperoxic gas during escape from 3000 kPa reduces the overall time with circulating VGE and, despite exposure to a maximum inspired partial pressure of oxygen of 1.8 MPa, symptoms of oxygen toxicity were not observed.