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Long Haul Danger For Astronauts; Blood Flow in Reverse- NASA study

Discovery that has important implications in future trips to Mars.

Spaceflight can halt and reverse blood flow in astronauts’ upper bodies, a NASA  study reports a startling discovery that has important implications in the future trips to Mars & other long-duration missions.

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NASA is known for decades that spaceflight is rough on the body and that spending a long period of time in orbit, unburdened by gravity, can cause astronauts’ muscles to lose mass and their bones to become more brittle.

Now, in the unexpected discovery, NASA scientists have found that spending time in space can affect how the blood flows through a major blood vessel in the upper body, causing it to halt or even flow backward which is a health risk that was unknown until now.

In the research study, published Wednesday in JAMA Network Open, researchers examined eleven healthy astronauts who stayed aboard the International Space Station for an average of 6 months. And during routine ultrasound assessments, by the 50th day of their space missions, 7 crew members were found to have reverse blood flow in their left internal jugular vein– a major blood vessel that runs down the neck side. It is responsible for draining blood from the brain, face & neck.

One of the astronauts was also found to have developed a clot in the internal jugular vein during spaceflight, and also a partial clot was discovered in another crew member after returning to Earth, according to the new study.

But this discovery is not necessarily a death knell for long-duration space travel, according to some experts, who said the study findings would eventually lead to the development of treatments & interventions to treat the health risks.

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Michael Stenger who is the manager of the Cardiovascular and Vision Laboratory at NASA’s Johnson Space Center in Houston and the new study’s senior author said this was an unexpected finding. They did not expect to see stasis and reverse flow which is very abnormal. On Earth, one would immediately suspect a massive blockage or a tumor or something like that, he added.

The study findings have major implications for long-haul space missions, including flights to Mars, which would require an interplanetary journey that needs up to 8 months.

Dr. Andrew Feinberg who is a professor of medicine at the Johns Hopkins University School of Medicine was not involved with this new study but who previously collaborated on research studies on the health effects of NASA astronaut Scott Kelly’s1 year mission at the space station. He said it is potentially a serious problem. If you get a blood clot in the internal jugular vein– the clot could travel to the lungs & cause a pulmonary embolism. If that happens on a long-term mission, the clot could be calamitous, he added.

The study on this began several years ago, as NASA attempted to investigate why nearly two-thirds of their astronauts reported blurry vision & impaired eyesight after spending months at the space station. In some of the cases, those impaired eyesight and vision problems persisted even after the astronauts had returned to Earth.

Stenger & his colleagues were tasked with understanding how the weightless environment affects the circulation of fluids in the upper body. Researchers found that without the ever-present tug of gravity on Earth, some astronauts’ bodies struggled to drain fluids normally.

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Stenger said this is why some astronauts get puffy faces because there is no gravity to pull down the 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).

The astronauts underwent ultra-sound assessments to measure their internal jugular vein before launch, at about fifty days into their spaceflight, 150 days into spaceflight & again approximately forty days after returning back to Earth.

During this, the internal jugular vein becomes engorged, but Stenger said he is most concerned about the crew members who experienced stagnant blood-flow in this blood vessel.

And if those blood cells are not moving, they start sticking to each other, and that is what we call a blood clot, he said. It is the same risk factor when you sit on an airplane for too long and could get clots in your legs, he added.

While the health risks of clots are serious, this discovery does not necessarily doom long-duration space travel.

Dr. Ben Levine, a cardiologist & professor of internal medicine at the University of Texas Southwestern Medical Center, Dallas, who was a consultant on the study, said that the engorgement seen in the blood vessels didn’t necessarily mean that the pressure inside them was high.

He said astronauts, use their arms a lot to move around, so he thinks there is plenty of blood flowing through the veins. He added he is intrigued by the study findings but not overly alarmed.

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Levine did acknowledge, however, that clots in the upper body could be potentially devastating & added that more research study is needed, particularly with regard to possible interventions.

In the study, the scientists saw improved blood flow when the astronauts wore a lower body vacuum suit that essentially pulls blood from the head into lower extremities.

Medicine in space is a journey into the extreme physiology discovering what happens when we leave Earth & how our bodies adapt, said Dr. Jan Stepanek who is a physician at the Mayo Clinic in Phoenix. He further added if we send people on missions to Mars, we need to find appropriate countermeasures, so they maintain muscle mass, bone density & cardiovascular fitness.

Dr. Scott Parazynski, a physician & retired NASA astronaut who flew on 5 space shuttle missions but was not involved with this study, said that although he is concerned about the potential consequences of the study findings, it would not deter him from flying in space.

Stepanek added that the study demonstrates how much more scientists have to learn about the health impacts of journeying into space.

he said after fifty years of human spaceflight, we may think we know everything, but it turns out that always nature has a way of surprising us.


Editor’s Note: Long Haul Danger For Astronauts; Blood Flow in Reverse- NASA study. Long Haul Danger For Astronauts, Discovery that has important implications in future trips to Mars, NASA Study Discovers Long-Haul Danger For Astronauts: Blood Flow In Reverse.

Ria Roy completed her Post Grad degree at the Visvesvaraya Technological University. She has a great grounding in the skills, including technical, analytical and research skills. She is a motivated life science professional with experience of working in famous research institutes