Illness and injuries during spaceflight

Most of the medical conditions that happen in space are not medical emergencies and can be treated on board. About 75% of all astronauts have taken medication during shuttle missions for conditions such as motion sickness, headache, sleeplessness, and back pain. Other common conditions include minor trauma, burns, dermatological and musculoskeletal injuries, respiratory illnesses and genitourinary problems.

Research on the medical emergencies that may occur in space include fatal and nonfatal arrhythmia, heart attacks, cardiac arrests, embolisms, massive hemorrhages, renal stone formations, fatal and non-fatal infections, and thrombotic complications. Of these conditions, only arrhythmia, renal colics, and infections have occurred in the history of spaceflight. The arrhythmia cases included occasional premature atrial contractions (PACs) and premature ventricular contractions (PVCs), which happened to 30% of astronauts at some point during periods of intense physical activity. Potentially serious arrhythmia cases (superventricular tachycardia) have also been reported. For example, during the Apollo 15 flight, one crew member experienced ventricular bigeminy; ventricular ectopy was reported on Skylab; and on Mir, a crew member experienced a 14-beat run of ventricular tachycardia.[5]

A case of coronary artery disease (CAD) has not been registered during any human space flight as of May 2014. However, due to the lack of public funding for larger space shuttles following the Columbia shuttle disaster in 2003, NASA has had to rely on the smaller Soyuz shuttles to send crews to space, which increased the waiting time for manned spaceflights and increased the average age of space crews since the mid-1990s. Since the risk of cardiovascular disease increases as people age, research on these diseases has become more important for space agencies - especially for long-term space missions. Other medical emergencies that have been observed in space include cases of urological [6][7] and dental emergencies,[8][9] as well as behavioural and psychiatric problems.

In a few cases, astronauts were brought back to Earth due to episodes of renal colic and arrhythmia, shortening their stays in space and possibly ending their missions.[2]

People who are exposed to harsh environments have suffered medical conditions that could be considered as analogs of the space environment. A sample of this information is presented in Tables 8-4 through 8-6.[4] The rate of these conditions is relatively low (10-50 cases per 100,000 people per day) and most were non-emergency (trauma, infection, psychiatric disorders), but they required an evacuation that would be impossible to provide in space. Crews living and working in harsh environments (Antarctic expeditions, submarines, and undersea habitats) had medical emergencies such as intracerebral hemorrhage, stroke, myocardial infarction, appendicitis, and bone fractures as well as cases of cancer and psychiatric illness. However, the overall rate of serious medical or surgical emergencies was low.

The most common emergencies were dental. For 100 British Polaris submarine missions, crew members required 30 fillings and 7 teeth extractions in total.[10] Dental problems have been the cause for a transfer at sea in the U.S. Polaris submarine program.[11] Extractions and fillings have also been required for missions in Antarctica.[12]

The calculated rate of significant illness or injury on submarines, Antarctic expeditions, military aviation and space flight was found to be approximately 0.06 cases per person-year.[13] If we use this data to evaluate the rate of occurrence of a medical emergency to a 2.5-year Mars mission, assuming six crew members, we get a rate of 0.9 cases per people/mission.[13] In other words, one significant medical event could be expected per Mars mission. These estimates are likely to be low, as they do not deal with the unique problems that are associated with the space environment: radiation effects and exposure and physiological adaptation to low gravity.[14]

As for cardiovascular emergencies, the yearly number of cases reported by age group for USAF aviators over 5 years was as follows: 0.0054% (30–34 years), 0.018% (35–39 years), 0.038% (40–44 years), 0.14% (45–49 years) and 0.13% (50–54 years).[15] In total, 21% were cases of sudden death and 61% were diagnosed and treated as myocardial infarction. Despite the physical screening that USAF aviators undergo, the first instance of cardiovascular illnesses in this group required serious medical intervention.[14] This data could apply to the astronaut corps as well, even if they undergo a more extensive medical assessment.[14]

In the submarine program, the most common general surgical condition was appendicitis,.[11] A case of death due to appendicitis was also reported among the participants of Antarctic expeditions.[4] Other serious conditions reported in the submarine program were traumatic amputations, fractures, and dislocations.[14] Depression and anxiety were the two most common psychiatric diagnoses made on submarines,[11] and they are frequent among researchers enduring long Antarctic winters.[16]

Radiation exposure could also cause medical problems due to the technical problems involved in the shielding of space craft, especially given the length of missions to Mars. Given that these missions could last several years at the level of technology available in 2014, age-related medical conditions would be likely to occur at the same rate as the general population. These probabilities have been assessed in astronaut pre- and post-flight health databases.[17][18]

Another problem related to long-term missions has been the design of medical care systems within space craft due to the limited amount of available space. Medical care systems for spaceships must include the technology necessary to heal exposure to toxic chemicals and gases, and chemical and electrical burns. Astronauts may also suffer from trauma aboard and during extra-vehicular activities outside space craft.

 This article incorporates public domain material from the National Aeronautics and Space Administration document "Human Health and Performance Risks of Space Exploration Missions" (NASA SP-2009-3405, pages 242-246).