Monitoring tissue oxygen saturation in microgravity on parabolic flights

Future spacecraft and crew habitats are anticipated to use a moderately hypobaric and hypoxic cabin atmosphere to reduce the risk of decompression sickness associated with extravehicular activity. This has raised concerns about potential hypoxia-mediated adverse effects on astronauts. Noninvasive technology for measuring tissue oxygen saturation (StO2) has been developed for clinical use and may be helpful in monitoring oxygenation during spaceflight. We conducted a technical evaluation of a handheld StO2 monitor during a series of parabolic flights, and then undertook a preliminary analysis of the data obtained during the flights from six individuals. The StO2 monitor operated normally in all gravity conditions. There was considerable variability in StO2 between and within individuals. Overall, transition to microgravity was associated with a small decrease in StO2 of 1.1±0.3%. This evaluation has established the basic function of this technology in microgravity and demonstrates the potential for exploring its use in space.