Staying healthy in space

Yuri Gagarin was the first human to fly to space in 1961. Since then, there have been 384 human space flight launches, the latest being SpaceX Crew-8, launched in March. Humans are a weak link in the man-mission-machine dynamics of space exploration due to the physiological limitations of their bodies. The space environment is hostile to them, with numerous stressors.

Space stress is mainly caused by zero gravity/microgravity, radiation, isolation, temperature and the bellicose environment during extravehicular activities. Loss of air pressure can make air rush out of the lungs, and dissolved gases can evaporate in seconds. The temperature in space reaches as low as -270ºC. Urine dump during shady periods instantly forms ice crystals. Effects of micro/zero gravity are felt even inside the space shuttle.

Space flight affects the human body, including space motion sickness, postural imbalance, cardiovascular system effects, and musculoskeletal, immunological, behavioural, and psychological effects. On landing in space, space motion sickness affects 95 percent of crew members, while it can be severe among 10 percent.

Astronauts can also lose appetite, have an unstable gait, nausea, vomiting, giddiness and vertigo. Most symptoms resolve in 36-48 hours after the body adapts. Crews with severe symptoms are treated with onboard medications. Postural imbalance occurs mainly due to the loss of gravity.

Puffy face, bird legs

The effect on the heart is described as ‘puffy face bird legs syndrome’. This occurs due to the lack of gravity and no downward pull of fluids. Body fluids shift upward and make one feel less thirsty, urinate more frequently, and have headaches and a stuffy nose. These make the face look puffier, and the wasting of calf muscles and the drainage of fluids upwards make the leg look like a bird’s leg.

A regular G suit, a liquid cooling garment, regular treadmill exercise, and medication help overcome this problem. Almost all space crew members complain of backache, fatigue, and decreased flexibility and endurance.

Long-duration space flights cause a decrease in body mass and leg volume,  atrophy of antigravity muscles (muscles of thigh and calf) and a decrease in weight due to muscle atrophy and demineralisation. Due to increased faecal and urinary calcium, the person can develop kidney stones, possible fractures, and disc disease in the long term. These are overcome by stretching exercises, wearing penguin suits, using fetal position sleep straps, and treadmill exercises against resistance.

The immune system is compromised mainly due to depression of white cell function and radiation exposure. There is a decrease in circulating red cell volume, often called ‘space flight anaemia’. Space crews are prone to injuries, with hand, back, and shoulder injuries being the most common.

Space crews are also tasked with performing extravehicular activities, during which they are exposed to micrometeoroid orbital debris (MMOD), foreign body inhalation, eye injuries and contact with toxic substances. Space suit and life support failures sometimes complicate the operations.

Many behavioural and psychological problems occur, such as changes in mood, isolation, and disturbed circadian rhythm. Spacecraft travel around Earth in about 90 minutes, experiencing sunrise and sunset sixteen times daily. This creates disturbances in circadian rhythm, alternating sleep patterns, and hormone levels.

To overcome this, space stations use Universal Coordinated Time (UTC), a global standard time. To create a sense of normalcy and promote healthy sleep patterns, the lights on the space station are dimmed from 9.30 pm to 6 am UTC. This simulates a nighttime period, even though the spacecraft is still experiencing rapid cycles of light and darkness outside.

Flight surgeons on the ground are in touch with the space crew daily via video conference once at a specific time. The crew also has medical emergencies and common illnesses such as eye, ear, nose and tongue.

Astronauts’ health problems persist for nearly three weeks after returning to Earth. Many have reported parking things in midair, such as toothbrushes, toothpaste, and caps, only to see them hit the floor. Astronauts undergo rehabilitation after returning to Earth as they are more prone to fractures due to calcium loss.

Astronauts are hailed as heroes upon their return, and rightly so, as the physical toll they take makes undertaking space missions daunting.

(The author is the group captain (Rtd) and aerospace medicine specialist, Indian Air Force)