And now, a recent NASA study has revealed that the blood flow in an astronaut's upper body can stop completely or worse -- could go in reverse -- if they spend too much time in zero-gravity space.
NASA
NASA researchers examined 11 healthy astronauts (nine male and two female), averagely aged around 46 years who stayed on the International Space Station for an average of six months.?
NASA began studying the impact of space flight a few years back when most astronauts reported blurry vision after spending months on the ISS.
For this test, astronauts were given ultrasounds to measure their left jugular veins (blood vessel is responsible to drain blood from the brain) before launch, 50-days into the flight and 150 days into the flight and 40 days after coming back to Earth.
Tests revealed that seven out of the eleven astronauts had signs of stalled or even reversed blood flow, specifically in their left internal jugular vein. This could result in blockage in the blood vessel and result in pulmonary embolism (blocking of one of the pulmonary arteries).
Now, this is very risky as it could severely impact not just the life of the astronaut, but also the mission's success.
However, researchers feel that this discovery won't cause any harm in new space missions and will in fact help in finding new treatments to help astronauts in space.
NASA
Michael Stenger, manager of the Cardiovascular and Vision Laboratory at NASA's Johnson Space Centre told NBC, "This was an unexpected finding. We did not expect to see stasis and reverse flow. That is very abnormal. On Earth, you would immediately suspect a massive blockage or a tumour or something like that."
More research on this will help in making space travel safer. NASA is also currently testing astronauts wearing a lower-body vacuum suit on the ISS that pulls blood down from the head into the lower limbs, making the body feel like it is on Earth.