Experiment to Predict Fainting in Astronauts

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BP Reg: Canadian Experiment Hopes to Predict Fainting in Astronauts

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For some astronauts, a long-term trip into space can literally leave them weak in the knees. During spaceflight, the human body has to adapt to the unusual microgravity environment. After spending many months aboard the International Space Station, it can be difficult to re-adapt to life as an Earthling under the pull of gravity. In fact, as much as a third of returning astronauts are wobbly on their feet, experience dizziness and even fainting episodes.

A new Canadian medical experiment hopes to answer why some astronauts are prone to fainting spells by predicting how they recover from rapid changes in blood pressure.

Led by University of Waterloo researcher Richard Hughson, Ph.D., and sponsored by the Canadian Space Agency, or CSA, the experiment known as BP Reg gets underway with Canadian Astronaut Chris Hadfield as its first test subject.

How our cardiovascular system works in space

In the low-gravity conditions of space, the cardiovascular system gets deconditioned because it doesn't have to work so hard against gravity to pump blood throughout the body. Also due to microgravity, there is more blood in the head and chest, which in turn reduces the workload on the heart.

But after returning to Earth from a long-duration flight, this adaptation of the cardiovascular system to space causes a decrease of blood pressure strong enough that bloods collects in their lower body, and so less blood flows to the brain. In some cases, astronauts experience dizziness, while others may faint because not enough oxygen-rich blood reaches the brain.

Countering the effects of spaceflight

CSA has already funded unique studies on how the cardiovascular system copes with weightlessness, involving 14 astronauts onboard the space station, as part of the CCISS and Vascular investigations. Taking the science one step further, BP Reg will, for the first time, offer insight into the degree of degradation in cardiovascular functions and identify the specific physiological mechanisms involved.

Hadfield, the first of eight astronaut participants in this study, will collect data before, during and after his mission using inflatable cuffs attached to his legs, looking for changes in blood pressure that may help predict risks of dizziness and fainting.

While not posing any health risks while in space, this cardiovascular adaption may have negative health implications for astronauts readapting to gravity after longer flights like for multi-year missions to Mars in the future.

Space research to help life on Earth

BP Reg will not only help scientists understand dizziness in astronauts, but may also lead to benefits for people right here on Earth -- particularly those predisposed to falls and resulting injuries, as seen in the elderly.

According to Dr. Hughson, approximately 6 percent of those over the age of 70 will faint and the recurrence rate is about 33 percent within two years. Fainting and falling are major contributors to bone fractures in the elderly, with approximately 35 percent mortality rate in individuals who fracture their hip.

Researchers expect that this unique Canadian project will directly help lead to developing methods that could be used to predict individuals in the general population who may be prone to fainting and falling.

This original story was written and published by the Canadian Space Agency on Dec. 11, 2012.

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