New study examines effects of extended exposure to weightlessness

Max Blenkin

As humans prepare for extended missions in space, to the moon and beyond, understanding of the physiological effects of living in microgravity has improved, with some a cause for concern.

New study examines effects of extended exposure to weightlessness
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A new study by a group of international researchers has found problems with the blood flow in six of 11 astronauts on the International Space Station (ISS) after around seven weeks in space.

What was found was described as “stagnant or retrograde flow in the internal jugular vein (IJV) on approximate flight day 50 and one crew member developed an occlusive internal jugular vein thrombus during spaceflight”.

“This cohort study found stagnant and retrograde blood flow associated with spaceflight in the IJVs of astronauts and IJV thrombosis in at least one astronaut, a newly discovered risk associated with spaceflight,” the study authors concluded.

“Lower body negative pressure may be a promising countermeasure to enhance venous blood flow in the upper body during spaceflight.”

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In the study, the authors sought to find out whether long-duration exposure to weightlessness was associated with impaired cerebral venous outflow and increased risk of jugular venous thrombosis.

Thrombosis is blood clotting within a vein or artery, a serious condition that can be fatal if undiagnosed or untreated.

The study authors said weightlessness was associated with blood flow stasis in the internal jugular vein, which might in turn lead to thrombosis in otherwise healthy astronauts.

They said this was a newly discovered risk of spaceflight with potentially serious implications.

“Exposure to a weightless environment during spaceflight results in a chronic headward blood and tissue fluid shift, compared with the upright posture on Earth, with unknown consequences to cerebral venous outflow,” they said.

For the study, internal jugular vein measurements were taken of the 11 astronauts from before launch and approximately 40 days after landing in three positions – seated, supine and 15 degrees head-down tilt. 

During the missions IJV measurements were acquired around 50 days and 150 day by way of ultrasonographic assessments of IJV cross-sectional area, pressure, blood flow and thrombus formation.

The astronauts were described as 11 healthy crew members with a mean age of 46.9, who spent a mean 210 days in space.

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