Imagine you're sealing a house before a hurricane. You can obsess over one slightly loose window, or you can check whether the whole weatherproofing system actually works. NASA's working group just told the agency to stop fixating on the window. The window in question is a patent foramen ovale (PFO) — a small flap-like opening between the heart's upper chambers that roughly 25% of adults carry from fetal development. In diving medicine, a large PFO is a known risk factor for decompression sickness because nitrogen bubbles can cross from venous to arterial circulation. The fear was that astronauts doing extravehicular activities on the lunar surface — working in low-pressure suits after prebreathe protocols — face the same arterial gas embolism risk. This working group, convened under NASA's Office of the Chief Health and Medical Officer, synthesized findings from a September 2024 PFO-DCS assessment, an April 2026 venous thromboembolism (VTE) working group, and the updated DCS prevention standard in NASA-STD-3001 Volume 2 Revision F. The headline conclusion: no universal PFO screening or exclusion of astronauts is recommended. Small PFOs (Grade 1-2) are deemed insignificant risk. For large PFOs (Grade 3+), the panel split — some members favored closure, others saw insufficient evidence that closure meaningfully reduces mission-health-event probability. The compromise: if crews are assessed and a large PFO is found, inform them and offer elective closure. That's a consent-based framework, not a gatekeeping one. On venous thromboembolism — a concern sharpened by the in-flight jugular vein clot discovery aboard the ISS — the panel concluded PFO presence is not a major VTE risk factor, even in the hypoxic habitat atmospheres planned for Artemis. This is notable because the VTE finding aboard ISS triggered significant concern about whether altered hemodynamics in microgravity and reduced-pressure environments compounded cardiac shunt risks. The panel says the two risk pathways are more independent than feared. Perhaps the most operationally significant recommendation concerns bubble monitoring. The group found no definitive link between venous gas emboli (VGE) bubble grades and DCS risk for prebreathe protocols involving partial gravity and ambulation — meaning the lunar surface scenario specifically. They explicitly recommended that ground-based studies stop excluding subjects solely for showing left ventricular gas emboli (LVGE), a practice that had been biasing research populations and producing unrepresentative data. That's a quiet but important methodological correction. The medication guidance may matter most for Artemis EVA timelines. The panel flagged that aspirin use for DCS prevention and common analgesics (acetaminophen, ibuprofen, naproxen, celecoxib) can mask DCS symptoms — a diagnostic nightmare when your patient is in a spacesuit on the lunar surface with a 1.3-second communication delay. Clear pre- and post-EVA medication protocols are now required, not merely suggested. This is a consensus document, not a research breakthrough. Its value is institutional: it consolidates two years of sub-panel work into operational guidance that will shape astronaut selection and EVA planning for Artemis III and beyond. The underlying tension — between conservative screening that might unnecessarily disqualify capable astronauts and permissive protocols that accept residual cardiac risk — remains unresolved for large PFOs. The panel chose data collection over exclusion, which is the right call given the evidence gap, but it means Artemis crews will be flying with acknowledged unknowns.
