EP128: Astronauts & Blood Flow in Space

Welcome to my podcast. I am Doctor Warrick Bishop, and I want to help you to live as well as possible for as long as possible. I’m a practising cardiologist, best-selling author, keynote speaker, and the creator of The Healthy Heart Network. I have over 20 years as a specialist cardiologist and a private practice of over 10,000 patients. Podcast Summary Introduction Dr. Warrick Bishop is a practicing cardiologist and author dedicated to educating patients about heart health through his podcast and videocast station. In this episode, he explores the fascinating intersection of space medicine and cardiology by examining how astronauts' bodies respond to microgravity, particularly focusing on unexpected changes in blood flow and vision. The episode bridges historical space exploration achievements with cutting-edge medical research discoveries made possible through astronauts' participation in space station experiments. Key Takeaways: Early space programs were concerned with basic bodily functions in zero gravity, but astronauts proved remarkably capable of adapting to the space environment despite discomfort. Approximately 10 years ago, NASA researchers discovered that astronauts in space were experiencing swollen optic nerves, flatter eyeballs, and vision changes—symptoms initially addressed simply by providing corrective glasses. A research team studied 11 astronauts' blood flow patterns in the jugular vein (the main neck vessel returning blood to the heart) across different body positions on Earth and compared findings to their physiology in space. Five of the 11 astronauts showed stagnant or reversed blood flow in their jugular veins while in space, meaning blood entering the brain through carotid arteries was not flowing back out normally, causing fluid accumulation. Stagnant blood flow in veins creates a significant risk of deep vein thrombosis (blood clots), a concern astronauts typically face after immobilization, such as following surgery. Female astronauts taking oral contraceptive pills face compounded clot risk, as hormonal contraceptives already increase clotting tendency when combined with blood flow stagnation. Commercial space tourism presents a critical medical concern, as paying passengers may lack the rigorous health screening and superior physiology of professional astronauts, making them vulnerable to dangerous clotting complications. Understanding how gravity loss affects bodily adaptation is essential for developing safety protocols and medical interventions for both professional astronauts and future space travelers.