Solving the case of the fainting astronaut

Heidemarie Stefanyshyn-Piper has fast become an internet favourite, for all of the wrong reasons.

Despite a stellar career as a captain in the US Navy, a mechanical engineer and twice a mission specialist on space shuttles, she is unfortunately best known for losing a tool bag while on a space walk – or extra-vehicular activity, in space-speak – which apparently can be spotted from Earth.

And before that unfortunate drama, she was captured by the cameras fainting twice at a news conference following re-entry from her first mission.

While video netheads may spoof her, which they have done mercilessly, there is actually a serious side to the fainting spells she experienced.

It is in no way unusual for astronauts to faint in the hours after landing, with conservative estimates suggesting that up to 40 per cent of all astronauts will experience fainting or at least dizzy spells on their return home.

To investigate the reasons behind this phenomenon, and to find out how to avoid it in future, a fascinating research project is underway on the International Space Station.

Called the Cardiovascular and Cerebrovascular Control on Return from ISS experiment (CCISS), this Canadian-led project aims to study the effects of long-duration spaceflight on the heart function and blood pressure of space crew.

There are plenty of earthly reasons for the project as well. The project involves learning more about long-distance data acquisition, the potential of telemedicine, common disease states like hypertension and blood pressure dysregulation, and the differences in blood pressure between men and women.

The team is led by principal investigator Richard Hughson from the University of Waterloo and co-investigators Andrew Blaber from Simon Fraser University in Vancouver and Kevin Shoemaker from the University of Western Ontario. These researchers are all exercise physiologists, also known as work physiologists, with an interest in the control of blood pressure and blood flow.

They are investigating the autonomic nervous system, which controls temperature, digestion, heart rate and blood pressure amongst others, and which does so automatically through a variety of different reflexes.

In space, where things are a little different, those reflexes are upset – or deconditioned – by the lack of gravity. What the researchers hope to do is understand more about the normal state of blood pressure by testing it in unusual circumstances.

“The point of all this is that you have reflexes that sense and regulate blood pressure, and these are very sensitive to gravity,” Kevin Shoemaker says.

“Just like training an athlete or training a muscle, it may be that this nervous system can be trained and can be de-trained. We are testing the idea that when you take away gravity you cause a deconditioning stimulus for this nervous system.”

When the system is deconditioned, and then returned to gravity, all of a sudden that gravity is sucking blood away for the heart, he says. “The system has changed and the net result, the most common symptom that you might see – and you can see it on Youtube – is astronauts fainting.”

Fainting or dizziness is the primary symptom of deconditioning, and no one is entirely sure what causes it, Shoemaker says. It could be due to the brain, the nervous system, the heart itself or the blood vessels (the most promising candidate). Either way, something has changed.

“If this were to occur long-term, we don’t know what kind of problems could develop. What we are able to do with the space station is study this system over six months, which is the longest time ever that people have had the opportunity to study the deconditioning of space travel.”

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