Special Hazards and EmergenciesExtravehicular activity (EVA), or spacewalking, poses a special health hazard. The astronaut
or cosmonaut must rely on the perfect functioning of a spacesuit and may have to experience changes of atmosphere and pressure between spacecraft cabin and spacesuit that can result in decompression sickness. In situations where cabin and spacesuit atmosphere and pressure are quite different, as in the U.S. Space Shuttle, lowered cabin pressure and prebreathing of oxygen prior to EVA is required.Few clear-cut medical emergencies have thus far occurred in space, although various medical problems have been indicated. For example, the U.S. astronaut James Irwin experienced heart
arrhythmias while walking on the Moon in 1971. Believed at the time to have been caused by an electrolyte imbalance, the arrhythmias may in fact have been an early symptom of the heart disease manifested by Irwin a few years following his Moon flight.The first known real medical emergency in space occurred when the Soyuz T14 crew cut short their mission and returned to Earth on Nov. 12, 1985. The commander, Vladimir Vasyutin, had developed an "acute inflammatory
infection" several weeks beforehand and had not responded to treatment with onboard drugs. The infection was accompanied by very high fever, insomnia, and intense irritability, and Vasyutin was relieved of command shortly before the crew's return. Once on Earth, he was hospitalized for a month. The exact type of infection was not officially disclosed, but the widespread opinion is that it was prostatitis. More recently, on July 30, 1987, another Soviet cosmonaut, Aleksandr Laveikin, was returned to Earth earlier than planned as a result of unexplained electrocardiogram readings that were mistakenly presumed to be arrhythmias.