Decompression sickness occurs when dissolved gases, mainly nitrogen, form bubbles in blood and tissue. NASA says astronauts face this risk during work outside a spacecraft because their pressurized suits operate at a lower pressure than the cabin. Its mitigation measures combine habitat conditions, suit pressure and breathing procedures designed to reduce nitrogen in the body. [S1]
The heart opening in question, a patent foramen ovale or PFO, persists in about 25% of people, according to NASA. It can allow gas bubbles to pass from the right side of the heart to the left, bypassing the lungs' normal filtration; bubbles reaching arteries may cause a neurological event such as a stroke. [S1]
Cases of decompression sickness in NASA's pressurized-chamber ground tests prompted the external review. Its assessment says that, even in an extreme high-risk exposure, excluding people with a PFO or treating the opening would not necessarily reduce decompression sickness or eliminate the risk. Its recommendation against screening rests on available evidence and the risk associated with current NASA decompression protocols and requirements. [S1]
For people taking part in ground engineering tests, the assessment calls for the same treatment capability as in research protocols: a treatment chamber immediately near the test site. It describes the ability to treat a case immediately as critical to test-subject safety. [S1]
Source documents
- Assessment of PFO as Related to DCS in the Spaceflight Environment and During Ground Testinghttps://www.nasa.gov/organizations/ochmo/assessment-of-pfo-as-related-to-dcs-in-the-spaceflight-environment-and-during-ground-testing/