Air travel is one of the safest modes of transport, but it places unique challenges on the body, according to a report from Independent Travel.
The aircraft cabin is pressurised at a level of up to 8,000 feet above sea level. This reduces the equivalent oxygen in the air from about 21% at sea level to 15% at altitude. A healthy person may not notice, but those with cardiopulmonary conditions such as chronic obstructive pulmonary disease or hypertension could be at risk.
Low cabin humidity dries out the skin, eyes, nose and throat, and increases water loss by up to 360ml an hour. This can thicken the blood and raise the risk of clotting-related conditions such as deep vein thrombosis.
Fainting is seen in at least one in three airline emergencies, often caused by postural hypotension. Alcohol and dehydration can contribute. Gastrointestinal issues are also common, with gas in the intestines expanding up to four times normal volume at altitude.
Mid-air cardiac emergencies are rare but have poorer outcomes than on land, and account for most in-flight deaths.
To reduce risks, the report advises drinking plenty of water, moving around every couple of hours, limiting alcohol, and staying on schedule with medication. People who have recently had dental work, surgery or been diving may face increased complications.