London: Long space mission induces a blood shift in astronauts from the bottom half of the body to the top that may lead to health problems, say researchers.
"We know that some astronauts experience vision problems some months into space flight and this may, in fact, be caused by the augmented fluid and blood volume shift to the upper body," said lead study author Peter Norsk, scientist from University of Copenhagen.
For the study, the team measured the volume of blood ejected by the heart into the blood vessels and monitored the blood pressure in eight astronauts aged between 45-53 years.
The recordings were taken before, during and after three-six months of space flight.
They found that the shift of blood and fluid from the lower to the upper body caused by weightlessness was much higher than previously thought.
The blood volume burden to the heart was also more than expected despite the heart rate remaining the same.
At the same time, blood pressure was considerably reduced, which corresponds to the effect of normal blood pressure medication against high blood pressure.
The discovery is important because during long duration missions, the blood volume burden to the heart could constitute a health problem.
Although the blood volume burden to the heart is higher than expected, blood pressure is lower because the blood vessels are more relaxed (dilated).
"In the future, the space flight factors that induce the fluid shifts and relaxation (dilatation) of the blood vessels should be identified," the authors noted.
The study was published in The Journal of Physiology.