Space travel dealt another health blow after new study finds astronauts experience reverse blood flow, leading to complications

This problem stems from the lack of the right gravity conditions in space. Without Earth's gravity, blood could get stagnated and flow backwards.


                            Space travel dealt another health blow after new study finds astronauts experience reverse blood flow, leading to complications

A future voyage to Mars and other long-duration missions could take a toll on the health of astronauts assigned on such missions, finds a NASA study. These astronauts could have an abnormal pattern of blood flow — reverse or stagnated — in their upper bodies, leading to other serious complications.

By spending an extended period of time aboard the International Space Station (ISS), the research team found that astronauts showed changes in a blood vessel running down their necks, the internal jugular vein (IJV), which transports blood from the brain, face and neck to the heart. The changes in this vein meant that the blood flow in the vein was either stagnant or flowing backwards, and was not emptying into the heart. 

“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 tumor or something like that,” Michael Stenger, manager of the Cardiovascular and Vision Laboratory at NASA’s Johnson Space Center in Houston, and the study’s senior author told NBC News.

The health risk could be serious. “If you get a clot in the internal jugular vein, the clot could travel to the lungs and cause a pulmonary embolism — that’s very dangerous. If that happens on a long-term mission, it could be calamitous,” Dr Andrew Feinberg, a professor of medicine at the Johns Hopkins University School of Medicine, who was not involved with the new study — but who previously collaborated on research on the health effects of NASA astronaut Scott Kelly’s one-year mission at the space station — told NBC news.

This problem stems from the lack of the right gravity conditions in space. On Earth, gravity does the job of pulling blood down from the head to the rest of the body. But this does not happen in space. Without Earth's gravity, blood could get stagnated and flow backwards, as seen in the astronauts who spent time at the ISS.

This is why some astronauts get puffy faces, because there’s no gravity to pull down those fluids circulating in the upper body. You will sometimes also see veins popping out in the neck, or in the head — which you can see with bald astronauts, in particular, explains Stenger.

Earlier studies have shown that gravity can affect health. According to NASA, after experiencing weightlessness in space, astronauts can see changes in their bones, muscles, cardiovascular system.

According to NASA, after experiencing weightlessness in space, astronauts can see changes in their bones, muscles, cardiovascular system. (Getty Images)

This is not the only health risk associated with space flight. NASA has made a list of other hazards, including exposure to space radiation, which increases the risk of cancer, damages the central nervous system, among others. 

In the new study, Stenger and team wanted to understand how a weightless environment affects the circulation of fluids in the upper body. The study included 11 astronauts, who underwent ultrasound assessments to measure their left internal jugular vein at four different time points: before launch, at about 50 days into their spaceflight, 150 days into spaceflight and again approximately 40 days after returning to Earth.

Of the 11 astronauts, the team found that six of them had developed stagnant or backwards blood flow in the vein, within a period of just 50 days. Stagnant blood flow could trigger blood clotting. They found one crew member with this condition.

But the side-effects can be reversed if astronauts wore a lower-body vacuum suit that essentially pulls blood down from the head into the lower body, according to the study.

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