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Monday, December 24, 2012

Are you fit for space travel?

Despite the mothballing of the space shuttle program, public and private funding for space travel is ongoing. Over the coming decades, space tourism as well as jobs requiring work in space are expected to climb. Both spaceports and new spacecrafts are in the planning or even construction phases. However, there is one major deficiency. Apparently, there’s currently no consensus on how to approve people for space travel. Researchers, led by Marlene Grenon from the University of California, San Francisco, think we need to remedy that lack.

Today, people who travel in space are almost uniformly fit and healthy and most are in the first half of their lives. That won’t always be the case. Grenon and her colleagues predict that doctors will one day be fielding questions about whether heart patients can withstand liftoff forces or about how long osteoporosis patients can safely live with low or no gravity. Zero gravity can cause a host of problems even in healthy people, how will it affect people who already have one or more infirmity?

So far, the evidence suggests that most people can tolerate the forces (or lack of forces) associated with space travel, even if they have pre-existing conditions. That said, we’re obviously far from knowing all there is to know about the medical effects of space travel. At present, the FAA is putting the onus of ensuring medical safety on the spacecraft operators, asking only for informed consent. This in turn means that prospective travelers will be seeking advice from their own doctors. For this reason, the researchers suggest that physicians begin to compile data and resources to share with their patients. The scientists have put together the following helpful chart as a starting point.

Hypothetical spaceflight considerations for common medical entities

Medical condition
Influence of spaceflight
Preflight intervention
Coronary artery disease
May increase the risk for cardiac dysrhythmias or myocardial ischaemia
If patient decides to fly, ensure that blood pressure and cardiac rhythm are properly controlled
Cerebrovascular disease
Possible altered flow patterns in a carotid lesion
Optimise medical treatment and consider repair as per current guidelines
Peripheral arterial disease
Volume shifts may exacerbate symptoms
Optimise medical management; consider treatment of critical limb ischaemia and claudication
Abdominal/thoracic aortic aneurysm
Impact of linear acceleration during launch could increase the risk of rupture
Consider treating (endovascular or open)
Aortic dissection (type B)
Impact of linear acceleration during launch could worsen the extent of the dissection
Consider treating (endovascular or open)
Chronic obstructive pulmonary disease/asthma
Symptoms may increase with the stress of flight
Optimise medical management
Increase in bone loss during spaceflight
Consider bisphosphonate treatments for longer duration flights (probably no effect for suborbital flights)
Possibility that immune suppression (and exposure to radiation) may exacerbate condition
Consider postponing flight
History of deep venous thrombosis
Theoretical increased risk of thrombosis with stasis and decreased use of lower extremities
Prophylactic low molecular weight heparin injections during flight
Gastrointestinal reflux
May exacerbate with the lack of gravity
Ensure that patients symptoms are well controlled with appropriate medical therapy
Transient infections (urinary tract infection, pneumonia, ears, skin infection)
Could exacerbate with effects on the immune system, increased growth of bacteria in space, unknown efficacy of common antibiotics with changes in pharmacokinetics and pharmacodynamics
Consider postponing flight until the acute process is resolved
Psychiatric problems
May exacerbate (or possibly improve) state
Ensure that the patient is not a threat to himself/herself or others

Unknown data on effects
Consider postponing the flight until after pregnancy

Elizabeth Preston has more on this over at Inkfish.

Grenon, S., Saary, J., Gray, G., Vanderploeg, J., & Hughes-Fulford, M. (2012). Can I take a space flight? Considerations for doctors BMJ, 345 (dec13 8) DOI: 10.1136/bmj.e8124