space medicine space medicine space medicine is a specialized field under aerospace medicine that focuses on the medical care of astronauts and spaceflight participants. the spaceflight environment poses many unique stressors to the human body, including g forces, microgravity, unusual atmospheres such as low pressure or high carbon dioxide, and space radiation. space medicine applies preventive medicine, population health, environmental health, and clinical medicine to medically screen and certify individuals for space flight; maintain their health before, during, and after space flight; and inform vehicle systems design to minimize the risk to human health and performance while meeting mission objectives. dan burbank and anton shkaplerov participate in a medical contingency drill in the destiny laboratory of the international space station. this drill gives crew members the opportunity to work as a team in resolving a simulated medical emergency on board the space station. astronautical hygiene is the application of science and technology to the prevention or control of exposure to the hazards that may cause astronaut ill health. both these sciences work together to ensure that astronauts work in a safe environment. medical consequences such as possible blindness and bone loss have been associated with human spaceflight. in october 2015, the nasa office of inspector general issued a health hazards report related to space exploration, including a human mission to mars. history hubertus strughold (1898–1987), a former nazi physician and physiologist, was brought to the united states after world war ii as part of operation paperclip. he first coined the term "space medicine" in 1948 and was the first and only professor of space medicine at the school of aviation medicine (sam) at randolph air force base, texas. in 1949, strughold was made director of the department of space medicine at the sam (which is now the us air force school of aerospace medicine (usafsam) at wright-patterson air force base, ohio. he played an important role in developing the pressure suit worn by early american astronauts. he was a co-founder of the space medicine branch of the aerospace medical association in 1950. the aeromedical library at brooks afb was named after him in 1977, but later renamed because documents from the nuremberg war crimes tribunal linked strughold to medical experiments in which inmates of the dachau concentration camp were tortured and killed. soviet research into space medicine was centered at the scientific research testing institute of aviation medicine (niiam). in 1949, a.m. vasilevsky, the minister of defense of the ussr, gave instructions via the initiative of sergei korolev to niiam to conduct biological and medical research. in 1951, niiam began to work on the first research work entitled "physiological and hygienic substantiation of flight capabilities in special conditions", which formulated the main research tasks, the necessary requirements for pressurized cabins, life support systems, rescue and control and recording equipment. at the korolev design bureau, they created rockets for lifting animals within 200–250 km and 500–600 km, and then began to talk about developing artificial satellites and launching a man into space. then in 1963 the institute for biomedical problems (imbp) was founded to undertake the study of space medicine. animal testing before sending humans, space agencies used animals to study the effects of space travel on the body. after several years of failed animal recoveries, an aerobee rocket launch in september 1951 was the first safe return of a monkey and a group of mice from near space altitudes. on 3 november 1957, sputnik 2 became the first mission to carry a living animal to space, a dog named laika. this flight and others suggested the possibility of safely flying in space within a controlled environment, and provided data on how living beings react to space flight. later flights with cameras to observe the animal subjects would show in flight conditions such as high-g and zero-g. russian tests yielded more valuable physiological data from the animal tests. on january 31, 1961, a chimpanzee named ham was launched into a sub-orbital flight aboard a mercury-redstone launch vehicle. the flight was meant to model the planned mission of astronaut alan shepard. the mission planned to reach an altitude of 115 miles, and speeds up to 4400 miles per hour. however, the actual flight reached 157 miles and a maximum speed of 5857 miles per hour. during flight, ham experienced 6.6 minutes of weightlessness. after splashing down in the atlantic ocean, ham was recovered by the uss donner. he suffered only limited injuries during flight, only receiving a bruised nose. ham's vital signs were monitored and collected throughout the 16 minute flight, and used to develop life support systems for later human astronauts. animal testing in space continues currently, with mice, ants, and other animals regularly being sent to the international space station. in 2014, eight ant colonies were sent to the iss to investigate the group behavior of ants in microgravity. the iss allows for the investigation of animal behavior without sending them in specifically designed capsules. north american x-15 rocket-powered aircraft north american x-15 provided an early opportunity to study the effects of a near-space environment on human physiology. at its highest operational speed and altitude, the x-15 provided approximately five minutes of weightlessness. this opportunity allowed for the development of devices to facilitate working in low pressure, high acceleration environments such as pressure suits, and telemetering systems to collect physiological data. this data and technologies allowed for better mission planning for future space missions. project mercury space medicine was a critical factor in the united states human space program, starting with project mercury. the main precaution taken by mercury astronauts to defend against high g environments like launch and reentry was a couch with seat belts to make sure astronauts were not forcibly moved from their position. additionally, experienced pilots proved to be better able to cope with high g scenarios. one of the pressing concerns with project mercury's mission environment was the isolated nature of the cabin. there were deeper concerns about psychological issues than there were about physiological health effects. substantial animal testing proved beyond a reasonable doubt to nasa engineers that spaceflight could be done safely provided a climate controlled environment. project gemini the gemini program primarily addressed the psychological issues from isolation in space with two crewmembers. upon returning from space, it was recorded that crewmembers experienced a loss of balance and a decrease in anaerobic ability. project apollo the apollo program began with a substantial basis of medical knowledge and precautions from both mercury and gemini. the understanding of high and low g environments was well documented and the effects of isolation had been addressed with gemini and apollo having multiple occupants in one capsule. the primary research of the apollo program focused on pre-flight and post-flight monitoring. some apollo mission plans were postponed or altered due to some or all crewmembers contracting a communicable disease. apollo 14 instituted a form of quarantine for crewmembers so as to curb the passing of typical illnesses. while the efficacy of the flight crew health stabilization program was questionable as some crewmembers still contracted diseases, the program showed enough results to maintain implementation with current space programs. effects of space-travel the effects of microgravity on fluid distribution around the body (greatly exaggerated) (nasa) main article: effect of spaceflight on the human body in october 2018, nasa-funded researchers found that lengthy journeys into outer space, including travel to the planet mars, may substantially damage the gastrointestinal tissues of astronauts. the studies support earlier work that found such journeys could significantly damage the brains of astronauts, and age them prematurely. in november 2019, researchers reported that astronauts experienced serious blood flow and clot problems while on board the international space station, based on a six-month study of 11 healthy astronauts. the results may influence long-term spaceflight, including a mission to the planet mars, according to the researchers. cardiac rhythms heart rhythm disturbances have been seen among astronauts. most of these have been related to cardiovascular disease, but it is not clear whether this was due to pre-existing conditions or effects of space flight. it is hoped that advanced screening for coronary disease has greatly mitigated this risk. other heart rhythm problems, such as atrial fibrillation, can develop over time, necessitating periodic screening of crewmembers’ heart rhythms. beyond these terrestrial heart risks, some concern exists that prolonged exposure to microgravity may lead to heart rhythm disturbances. although this has not been observed to date, further surveillance is warranted. decompression illness in spaceflight in space, astronauts use a space suit, essentially a self-contained individual spacecraft, to do spacewalks, or extra-vehicular activities (evas). spacesuits are generally inflated with 100% oxygen at a total pressure that is less than a third of normal atmospheric pressure. eliminating inert atmospheric components such as nitrogen allows the astronaut to breathe comfortably, but also have the mobility to use their hands, arms, and legs to complete required work, which would be more difficult in a higher pressure suit. after the astronaut dons the spacesuit, air is replaced by 100% oxygen in a process called a "nitrogen purge". in order to reduce the risk of decompression sickness, the astronaut must spend several hours "pre-breathing" at an intermediate nitrogen partial pressure, in order to let their body tissues outgas nitrogen slowly enough that bubbles are not formed. when the astronaut returns to the "shirt sleeve" environment of the spacecraft after an eva, pressure is restored to whatever the operating pressure of that spacecraft may be, generally normal atmospheric pressure. decompression illness in spaceflight consists of decompression sickness (dcs) and other injuries due to uncompensated changes in pressure, or barotrauma. decompression sickness decompression sickness is the injury to the tissues of the body resulting from the presence of nitrogen bubbles in the tissues and blood. this occurs due to a rapid reduction in ambient pressure causing the dissolved nitrogen to come out of solution as gas bubbles within the body. in space the risk of dcs is significantly reduced by using a technique to wash out the nitrogen in the body's tissues. this is achieved by breathing 100% oxygen for a specified period of time before donning the spacesuit, and is continued after a nitrogen purge. dcs may result from inadequate or interrupted pre-oxygenation time, or other factors including the astronaut's level of hydration, physical conditioning, prior injuries and age. other risks of dcs include inadequate nitrogen purge in the emu, a strenuous or excessively prolonged eva, or a loss of suit pressure. non-eva crewmembers may also be at risk for dcs if there is a loss of spacecraft cabin pressure. symptoms of dcs in space may include chest pain, shortness of breath, cough or pain with a deep breath, unusual fatigue, lightheadedness, dizziness, headache, unexplained musculoskeletal pain, tingling or numbness, extremities weakness, or visual abnormalities. primary treatment principles consist of in-suit repressurization to re-dissolve nitrogen bubbles, 100% oxygen to re-oxygenate tissues, and hydration to improve the circulation to injured tissues. barotrauma barotrauma is the injury to the tissues of air filled spaces in the body as a result of differences in pressure between the body spaces and the ambient atmospheric pressure. air filled spaces include the middle ears, paranasal sinuses, lungs and gastrointestinal tract. one would be predisposed by a pre-existing upper respiratory infection, nasal allergies, recurrent changing pressures, dehydration, or a poor equalizing technique. positive pressure in the air filled spaces results from reduced barometric pressure during the depressurization phase of an eva. it can cause abdominal distension, ear or sinus pain, decreased hearing, and dental or jaw pain. abdominal distension can be treated with extending the abdomen, gentle massage and encourage passing flatus. ear and sinus pressure can be relieved with passive release of positive pressure. pretreatment for susceptible individuals can include oral and nasal decongestants, or oral and nasal steroids. negative pressure in air fill spaces results from increased barometric pressure during repressurization after an eva or following a planned restoration of a reduced cabin pressure. common symptoms include ear or sinus pain, decreased hearing, and tooth or jaw pain. treatment may include active positive pressure equalization of ears and sinuses, oral and nasal decongestants, or oral and nasal steroids, and appropriate pain medication if needed. decreased immune system functioning astronauts in space have weakened immune systems, which means that in addition to increased vulnerability