A long balloon trip is a hazardous business. Crew members have to spend days together in a confined space, and if a health problem arises they cannot call a doctor.
The crew's bodies are put under immense strain during the days of a major flight. This means they must get proper rest and avoid stressful situations as much as possible - no easy task given the nature of their challenge.
Exhaustion can severely impair performance, and is caused by insomnia, illness, stress and overwork. Although the cabin is heated to 15°C, temperatures outside are well below freezing - and the higher they go, the colder it gets. Should the cabin's heating systems fail, the balloonists will face two main threats - hypothermia and frostbite.
Hypothermia symptoms take effect in stages, starting with bouts of shivering and an inability to think straight. It progresses until the sufferer loses consciousness, their breathing comes close to stopping and the pulse is extremely weak. It can be prevented by wearing many layers of clothing, drinking plenty of fluids and hot drinks (but not alcohol) and keeping well nourished.Maintaining movement to keep circulation up is also advised.
In the event of cabin decompression, the crew will have more than the cold to contend with - they will be severely deprived of oxygen due to the lower concentrations at altitude.
However, the body requires the same amount of oxygen regardless of how much is available, so the breathing rate increases to compensate - even when the body is at rest.
Altitude itself also has negative effects on health. If the human body is left exposed at high altitude without acclimatisation, the effects can be devastating. Sometimes the combination of high altitude and lower atmospheric pressure causes fluid to leak from the capillaries.
From take off to touch down the crew spend all their time in a cramped cabin This can cause fluid build-up in both the lungs and the brain. In the lungs this can result in high altitude pulmonary oedema, where the fluid prevents effective oxygen exchange. As the condition worsens the level of oxygen in the bloodstream decreases. This can lead to cyanosis (where the skin turns blue), impaired cerebral function, and death. Fluid build-up in the brain causes high altitude cerebral oedema.
Symptoms include headache, loss of co-ordination, weakness, and decreasing levels of consciousness including, disorientation, loss of memory, hallucinations, psychotic behavior, and coma. It occurs after a week or more at high altitude, and can lead to death if not treated promptly.
Balloonists will have tp prepare for such eventualities.