Space Medicine: Out of Sight

Outer space is, without a doubt, a dangerous place. Now that we’ve landed a probe on a comet (Yes, a comet! If you haven’t heard about the incredible Rosetta mission yet, check it out here.), venturing out into that great yonder may not seem quite as daunting as it did before. But 53 short years ago, the final frontier was utterly fearsome. While we’d collected data and speculated widely about what might await the brave humans launched out of our atmosphere, we actually had no idea what would happen. What we did know was that lots of things could go wrong. Incidentally, that’s still true.

What’s the worst that could happen?

The concerns raised about the health hazards of space travel were myriad, ranging from engineering issues like maintaining cabin pressure, oxygen levels, and temperature, to coping with the many environmental challenges inherent to spaceflight, such as micrometeorites, radiation, and weightlessness. There was even worry that humans wouldn’t be able to adjust to the 90 minute day/night cycle of space (a 45 minute day followed by a 45 minute night)- thankfully, curtains did the trick- and that they would have abnormal psychological reactions to leaving earth, either from joy (“space euphoria”) or isolation (“break-off phenomenon”)1.

Fortunately, nearly none of these fears have been realized. The most common complaints of crewmembers by far are the symptoms of space adaptation: nasal congestion, back pain, motion sickness, insomnia, headache, and constipation5. Don’t get me wrong, space definitely has an impact on the human body. In zero gravity, body fluids shift toward the head, blood and body fluid volume decrease, bones and muscles begin to atrophy, and hormone levels are altered. Not only can these changes affect human health, they may pose serious challenges to medical care by making it difficult to determine the appropriate treatment and drug dosages for astronauts3.

space medicine
Is there a doctor in the house?

The right stuff

There are three main challenges to providing health care to space crew members: 1) the limited space available for medical equipment in a space shuttle, 2) the absence (usually) of medically trained mission crew members, and 3) potentially unfamiliar medical conditions that may be unique to space. Because of space constraints, the International Space Station (ISS) has a very limited capacity for sterilizing equipment, analyzing bodily fluids, providing suction, providing care after wound closure, dental care, or treating bone fractures5. There are no x-ray or MRI machines, so diagnostics depend on portable ultrasound devices, which, thankfully, are rapid and accurate4. There is no integrated system with ground operations (i.e. Houston) for tracking medical information or medical data collected in spaceflight. This is particularly problematic because the crew is responsible for collecting whatever data is needed to determine the right treatment for an afflicted colleague, which can be difficult, given their limited medical training5.

Because medical care during missions is so restricted, NASA heavily relies on preventative measures: finding the so-called “right stuff”. Astronauts are only allowed to fly if they pass rigorous physical and psychological exams5. If something does go wrong, the ailing crewmember is in the hands of the Crew Medical Officer (CMO). CMOs are usually not physicians, and receive only roughly 80 hours of additional training in medical diagnosis and treatment4. Luckily, the CMOs are not totally on their own. Although there is limited communication with Earth, astronauts are able to regularly consult physicians on the ground2.

Space medicine brought to earth

As spaceflights increase in duration, potentially stretching out for years or even lifetimes, there must be an expansion of extraterrestrial medical resources. Up to this point, there has been- however remote- the possibility of returning to earth in the event of a medical emergency. As we foray farther afield, that will no longer be true.

But even if the telemedicine techniques developed for spaceflight, portable ultrasound for diagnosis and consultation via satellite, become insufficient for life in space, they are incredibly helpful here on earth. Starting in the 1970s with the aid of NASA’s satellites, telemedicine has been used to provide medical care to remote and underserved regions of the world2,4. Since these programs started, they have been used for regular care, disaster relief, and to foster international medical cooperation (in a program delightfully entitled Spacebridge)2. The final frontier may be closer than you think.

References

  1. Berry, C. (1967). Space medicine in perspective. Journal of American Medical Association, 201(4):86-95.
  2. Doarn, CR, AE Nicogossian, & RC Merrell. (1998). Applications of telemedicine in the United States Space Program. Telemedicine Journal, 4(1):19-30.
  3. Garshnek, V. (1993). Astromedine and astrolaw. Space Policy, 95-98.
  4. Kufta, JM & SA Dulchavsky. (2013). Medical care in outer space: a useful paradigm for underserved regions on the planet. Surgery, 154(5):943-945
  5. Palowski, W. Exploration Medical Capability Evidence Report. NASA. 8 November 2013. Web. 15 November 2014. https://humanresearchwiki.jsc.nasa.gov/index.php?title=Exploration_Medical_Capabilites_Evidence_Re port

Image source: Creative Commons, http://en.wikipedia.org/wiki/NASA_Astronaut_Group_16

Decompression Sickness: Into the Unknown

Aliases: decompression sickness, DCS, the bends, caisson disease

Exploring wouldn’t be an adventure without risk, and the brave few who push exploration to its limits, diving into our planet’s depths or rocketing out of our atmosphere, are certainly taking their chances. Voyagers to extreme environments, like astronauts or deep-sea divers, can suffer from many unusual ailments, including decompression sickness (DCS), also know as “the bends”. DCS is a condition with a litany of symptoms (see below) that arises from a hyperbaric exposure– that is, being in a high or low-pressure environment, like the deep ocean or outer space.

While exploring, excess gas (usually nitrogen) is stored in body tissues and upon returning to earth’s normal surface pressure, it is released, potentially leading to all kinds of issues. The greater the amount of pressure change the body experiences and the longer that experience lasts, the more gas is sequestered, and the more gradually the person must be brought back to normal surface pressure3. Historically, DCS has been a big problem for people working at high pressures, such as tunnel workers, peaking at an incidence rate of 24%. Greater awareness and new technology has markedly reduced it; only 5 out of every 10,000 (0.05%) of modern recreational dives result in DCS2.

Although great strides have been made in eliminating DCS, there is room for improvement. Current decompression tables, which dictate the rate of return to normal pressure after a hyperbaric exposure, were developed in 1971, and need updating1. In part, the issue is DCS itself: the condition remains mysterious. It’s still unclear how and where gas storage happens in the body, making accurate predictions about the effects of decompression difficult2. It turns out, if you venture into the unknown, you might bring a piece of it back with you.

decompression sickness
Good under pressure.

Cause: When a person breathes air that is either under much greater or much less pressure than it is at the earth’s surface, excess gas is stored in their tissues. When they return to breathing air at normal surface pressure, the body wants to expel the gas, and it will be released from the tissue into the bloodstream to eventually be exhaled3.

Consequence: After a hyperbaric exposure, the excess gas released into the bloodstream can form bubbles that interfere with blood flow and tissue oxygenation. This can lead to an impressive suite of symptoms, including mottling of the skin, joint pain, numbness or tingling, coughing or shortness of breath, dizziness, itching, fatigue, loss of coordination, tremors, weakness, paralysis, and collapse or unconsciousness3. Symptoms usually appear within 24 hours, but can take up to two days. Typically, the first sign of DCS is a dull, aching pain that can only be localized to a general region of the body. Mild cases often go unreported, and resolve themselves. More severe cases typically cause pain (20-50% of cases) and neurological symptoms, such as numbness (20-40% of symptoms)2. DCS can be very painful and– in the worst instances– fatal1.

Cure: There is no hard and fast cure for DCS. The condition is typically treated with recompression therapy, where patients are put in a pressurized room to redissolve the gas that has been released into their bloodstream, removing the bubbles. Hyperbaric oxygen therapy (HBO), breathing pure oxygen in a pressurized room, is also commonly used. HBO prevents further gas uptake, and accelerates the removal of stored excess gas and the delivery of oxygen to potentially deprived tissues throughout the body. Prevention is critical in combatting DCS. Workers that are regularly exposed to high or low pressure environments use decompression chambers, rooms where the pressure is controlled, to gradually bring themselves back to surface pressure. The same principle is followed when divers resurface slowly, allowing time for their bodies to readjust. Exercise and being fit can prevent its onset, as can oxygen prebreathing, which rids the body’s tissues of nitrogen and reduces bubble formation2.

References

  1. Decompression Sickness and Tunnel Workers. Centers for Disease Control and Prevention. 19 September 2012. Web. 15 October 2014. http://www.cdc.gov/niosh/topics/decompression/
  1. Mahon, RT, & DP Regis. (2014). Decompression and decompression sickness. Comprehensive Physiology, 4: 1157-1175.
  1. Scuba diving. Centers for Disease Control and Prevention. 1 August 2013. Web. 15 October 2014. http://wwwnc.cdc.gov/travel/yellowbook/2014/chapter-2-the-pre-travel-consultation/scuba-diving

Image source: Wikimedai Commons, http://commons.wikimedia.org/wiki/File:Decompression_chamber.jpg