Could a tiny heart hole worsen altitude sickness?

This study looks at how a small opening in the heart, called a patent foramen ovale (PFO), affects blood flow and oxygen levels during exercise and simulated high altitude. About a third of people have this opening, which may allow oxygen-poor blood to mix with oxygen-rich blood, potentially increasing the risk of high-altitude pulmonary edema (HAPE), a dangerous fluid buildup in the lungs. Researchers will measure pressures inside the heart and blood flow through the PFO in adults with and without a history of HAPE. The goal is to understand whether this heart opening contributes to altitude sickness, which could help identify at-risk individuals.