Friday, March 18, 2011

A Giant Leap for Medicine

Image Credit: NASA
Fifty years after the first manned space flight, medical science is coming to terms with the unique challenges to the human body posed by life in zero gravity. The head of the European Space Agency's Medical Operations tells Eimear Vize about its progress.

Stepping out of a spacecraft to stretch your legs, take in the local scenery and pick up a sandwich are just not options when you’re hundreds or thousands of kilometres outside earth’s atmosphere.

While there are countermeasures for the strain our bodies experience during a long car journey or flight, keeping astronauts fit and healthy as they travel through the solar system gives rise to a multitude of serious medical concerns.

The concerted efforts of scientists, doctors and industry working to alleviate the stress of zero gravity on our terrestrial bodies has led to the advancement of a unique medical specialty - space medicine. Defined as the medical science of the biological, physiological, and psychological effects of space flight on humans, space medicine strives to both relieve the effects of debilitating conditions in space and to prevent them arising.

2011 marks the 50th year of manned space flight. Since the first blast-off by Russian cosmonaut Yuri Gagarin in 1961 and man’s historic steps on the moon in 1969, human activity in space has increased steadily. In fact, more than 500 people from 38 countries have made that incredible journey into space, according to the Fédération Aéronautique Internationale (FAI).

The reality is that space travel has its health hazards. Weightlessness, for example, is not a benign state. It has a multi system impact, including bone demineralisation, muscle atrophy, impaired co-ordination and neurovestibular tracking skills, cardiovascular deconditioning and orthostatic intolerance, motion sickness, and altered hormone concentrations. And that’s before you address the harmful effects of prolonged exposure to solar and galactic radiation.

“In the beginning of space life it was not known if humans could survive in space but luckily, with a little time, the biological system in the human is very adaptable,” says Dr Volker Damann, Head of the European Space Agency’s Medical Operations and a flight surgeon to many human space flight missions.

Dr Volker Damann
“An astronaut will experience dizziness and disorientation during their first few days in the microgravity environment. We call it space adaptation syndrome. Their vestibular system, which is key to our sense of balance, motion and body position, is pretty much messed up because of the lack of gravity in space.

“The system shuts down a little, gets disoriented and the usual reaction is stomach awareness, nausea, and even vomiting in roughly 70 to 75 per cent of new space flyers. There are varying degrees, not everyone is vomiting or completely disabled. Usually those symptoms have disappeared after about two days, that’s the initial adaptation,” the German doctor tells Scope.

Other body functions do not adapt as quickly, however, and changes in certain other physiological functions may prove to be lasting and could cause serious problems, especially when astronauts return to the "normal" gravity of Earth.

“Every part of our body has a purpose. Our bones and muscles are built to be upright, to work in a one gravity, 1G, environment. But if we leave the gravity field of Earth, our bodies no longer need the full strength of the skeletal and muscular systems for support of their ‘upright’ position. When the muscles and bones are not used, they deteriorate or ‘decondition’,” explains Dr Damann.

For short space flights of a week or so, these changes are small and pose no real problem, but for longer space flights, they are potential causes of concern, particularly as the heart is one of those muscles that will begin to deteriorate within the first two to three weeks in space.

“The heart muscle doesn’t need to pump upwards to the brain anymore, as there is no up or down, so the heart begins to decondition. We have developed countermeasures for every space flyer that is in space longer than two weeks. We impose a very strong exercise regime on the astronauts on a daily basis, two hours of exercise per day, to keep their cardiovascular condition and to keep muscle strength.

“Of course it takes longer to get rid of bone mineral or calcium, that takes weeks and months, but you can roughly consider a general bone loss of one to two percent per month. There are some bones that may loose even more mineral content - all of the weight-baring bones such as your femur, your pelvis, some of the lumbar spine for example may lose more calcium because they are used less. So after a six-month mission, there could be a bone loss of 12 per cent or more. That’s even with the daily exercise regime.”

An almost immediate effect, within a couple of hours to one day of entering microgravity, is a loss of blood volume. Under normal conditions, blood and other body fluids tend to pool in the legs. To counter this effect of gravity, veins in human legs have evolved valves that open and close to assist blood circulation back up to the heart. In orbit, however, this situation changes dramatically.

“All of a sudden our five litres of blood are equally distributed throughout the body. So the pressure sensors in our heart and other areas suddenly measure there is more blood, that there is high blood pressure. If there is high blood pressure this is usually a trigger to the kidney to get rid of fluid.

“So very quickly the kidney will excrete more fluid, resulting in a general reduction in the blood volume by roughly one litre, which is perfectly okay in space, but when you come back to earth then there may be problems. Your heart muscle may not be as conditioned as on earth, you have less blood, so what happens when you stand up getting out of the shuttle, you faint.

“There is nothing we can do about the loss of blood volume but shortly before they return to earth we get the astronauts to regularly drink in the order of one and a half to two litres of fluid just to replenish the lost volume.

“We are pretty good at maintaining cardiovascular fitness and muscle strength but there is a big problem still with bone loss,” Dr Damann admits.

“When astronauts return to earth, gradually we increase their workloads, we change their exercise regime, we do a lot of physiotherapy, then of course jogging and walking once the vestibular symptoms have improved.”

Whether lost bone is fully regained once astronauts return to Earth's gravity is not entirely certain. Medical experts fear that the body's calcium balance might be restored before the bones have replaced all the lost minerals, resulting in permanent damage.

Although cortical bone may regenerate, space physicians are concerned that loss of trabecular bone may be irreversible. According to Dr Jay Shapiro, team leader for bone studies at the National Space Biomedical Research Institute in the US, "The magnitude of this effect has led NASA to consider bone loss an inherent risk of extended space flights."

Italian astronaut Paolo Angelo Nespoli
Space physicians are just as concerned with the psychological effects of long-term stays on space stations as they are about the physical effects. In December 2010, Italian astronaut Paolo Angelo Nespoli embarked on Europe's third long-duration space mission. Currently on board the International Space Station (ISS), his mission will span approximately 180 days.

“Astronauts are highly-trained professionals but we are all human, stress and worry, overwork or boredom can all take an emotional toll. One component of stress is related to certain risks that human space flight has, of course if you start thinking about the risk while you’re sitting on the rocket then it’s really to late,” says Dr Damann. “So, of course, when the astronaut is assigned to a mission they have to think and talk about the risks they are taking; they have to discuss it with their families and go through “what if” scenarios so they are mentally prepared.

“When they are in space, we try to avoid putting them under additional stress in terms of overloading them with work for six months, or not loading them enough so that boredom becomes an issue. They need a good balance, a regular schedule,” he adds.

The astronauts rise early in the morning and work regular hours on weekdays. Each part of their day is planned, including time allotted for sleep, exercise, chores and meals. Saturday is typically divided between science and relaxation. Sunday is a day of rest. The astronauts can unwind by reading, watching a movie or listening to music. Family conferences are scheduled on Sunday when they can enjoy a two-way audio-video chat with their loved ones back on Earth.

“It’s really about giving them a regular schedule that they are happy with. One of the rules of responsibility for our team in the medical office is to be like union representatives for the astronauts, so to speak. Do they have enough leisure time? Do they get enough sleep? Do they have enough distraction? Are we overloading them with work? If stress occurs we have to be able to spot the signs.”

Two astronauts demonstrate the unique effects of zero gravity
Dr Damann’s medical team also includes psychologists who hold one-to-one psychological conferences each fortnight with members of the ISS crew. “We don’t expect any major issues but talking about work life and family life can really help the astronauts, particularly being so far removed from home if something happens, like a child is injured.”

Last summer saw a 520-day simulation of a Mars human exploration mission get underway in Russia, with researchers studying the mental and emotional impact on volunteers confined in space travel conditions for an extended period. The six men "landed" on Mars on Saturday 12 February and spent  a few days researching the planet before beginning the months-long return flight to Earth, expected to be the most challenging part of the mission.

While the physical and psychological impact of such a long-duration mission will be challenging, the biggest concern for space physicians is prolonged radiation exposure, which can lead to numerous health problems, including nausea, vomiting, fatigue, skin injury and changes to white blood cell counts and the immune system. Longer-term radiation effects include damage to the eyes, gastrointestinal system, lungs and central nervous system. Exposure also increases cancer risk.
Soviet cosmonaut Valentin Lebedev, who spent 221 days in Earth’s orbit in 1982, lost his eyesight to progressive cataract. Lebedev stated: “I suffered from a lot of radiation in space. It was all concealed back then, during the Soviet years, but now I can say that I caused damage to my health because of that flight.”

“Radiation is still our biggest problem,” agrees Dr Damann. “It is not at all solved. We know that in earth orbit astronauts still receive a significant radiation dose depending on the solar cycle, and if we go beyond earth, further out towards the moon and Mars there is an increase in galactic radiation, which increases significantly the radiation dose.

“We know how harmful high-dose radiation is to the body but the problem in space is low-dose radiation over a long duration. We can measure radiation, that gives us a number, but the number doesn’t tell us what is the impact on the individual cell, on their DNA etc. There still needs to be a lot of research to see what are the genetic effects, what are the risks for the individual, and research to provide the appropriate shielding for the astronauts.”

Some protective measures are being taken, for example, NASA has developed a light weight polyurethane “brick”, which lines the sleep stations of the astronauts and provides some degree of shielding.

Dr Damann remarks that one of the most effective shields against radiation is water, but with one kilogram of upload to the space station costing roughly $25,000, this option is prohibitively expensive and logistically fraught.

“The only thing we can currently do is to measure the amount of radiation exposure that we can protocol and document in case there is some cancer development, for example, in the astronaut’s later life,” he says, detectibly unhappy with this status quo.

At present, the countermeasure for radiation is limiting astronaut exposure, which means limiting the amount of time they're allowed to be in space. But on a long-term mission of exploration, the astronauts will have to be in space for months on end, and, importantly, the type of radiation in deep space is more damaging than the kind in low earth orbit.

If humans ever hope to make long voyages to distant planets, we will first have to find a way to protect astronauts from this radiation.

But Dr Damann and his colleagues are already making plans for a future in which exploration-class missions will be a reality. Their focus, naturally, is on the provision of medical care delivered by appropriately skilled physicians, who may one day serve on-board such exploration-class spaceships.

“What we plan in the short to medium term is getting space medicine into the normal medical curricula in medical universities around Europe. There are only very few institutes on this globe that are dealing with space medicine, we want to expand that considerably.

“We’re still at the planning stage but we’re starting to make progress. For example, last year we started a new masters programme for space physiology and health with Kings College London. This now runs for the first year. We want to create a network of other universities, maybe even a virtual campus with Italian universities who may have a certain specialty that is interesting for life sciences, or a German university or an Irish university,” said Dr Damann, who has been described as a visionary in the career roadmap for life scientists and clinicians interested in space. 
With a background in radiology and nuclear medicine, the majority of Dr Damann's training in space medicine was 'on the job' with the German Space Agency DLR and later, the European Space Agency.

“We are also preparing a job analysis for the role of space physicians in the future and how we would structure their education. We are at the very beginning of creating certain modules in universities that we can combine and which young people can select from very specific masters programmes in life science research activities or biomedical engineering or space medicine.”

Dr Leonard “Bones” McCoy
And how does he envisage the future role of doctors in space medicine should long-duration exploration of our solar system become more technologically feasible in the decades ahead? How conceivable is a medical position such as the one occupied by Dr Leonard “Bones” McCoy in the cult TV series Star Trek?

“Well, that’s one aspect that hopefully will change in the future, that we will have a physician on board a spacecraft. If you look back in history there have always been ships doctors on board every sea voyage or cruise. Only in space flight have we not done that yet. So I think it’s about time that we get a physician on board and into orbit.”
So space may yet be the new medical frontier. To paraphrase another Star Trek character: “It’s medicine, Jim, but not as we know it.”

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