Oxygen exposures at NASA's Neutral Buoyancy Lab: a 20-year experience.

Oxygen exposures at NASA's Neutral Buoyancy Lab: a 20-year experience. Undersea Hyperb Med. 2018 Jul-Aug;45(4):427-436 Authors: Walker SC, Garbino A, Ray K, Hardwick R, Fitzpatrick DT, Sanders RW Abstract Astronauts training for extravehicular activity (EVA) operations can spend many hours submerged underwater in a pressurized suit, called an extravehicular mobility unit (EMU), exposed to pressures exceeding 2 atmospheres absolute (ATA). To minimize the risk of decompression sickness (DCS) a 46% nitrox mixture is used. This limits the nitrogen partial pressure, decreasing the risk of DCS. The trade-off with using a 46% nitrox mixture is the increased potential for oxygen toxicity, which can lead to severe neurologic symptoms including seizures. Suited runs, which typically expose astronauts of 0.9-1.1 ATA for longer than six hours, routinely exceed the recommendation for central nervous system oxygen toxicity limits (CNSOTL) published by the National Oceanic and Atmospheric Administration (NOAA). Fortunately, in over 50,000 hours of suited training dives spanning 20 years of EVA training operations at NASA's Neutral Buoyancy Laboratory (NBL) there has never been an occurrence of oxygen toxicity. This lends support to anecdotal sentiment among certain members of the hyperbaric community that the NOAA CNSOTL recommendations might be overly conservative, at least for the oxygen pressure and time regime in which NBL operates. The NOAA CN...
Source: Undersea and Hyperbaric Medicine - Category: Sports Medicine Authors: Tags: Undersea Hyperb Med Source Type: research