If you and your group act on the advice given so far, you are very unlikely to meet these complications. Edema (spelled oedema in Britain) is medical jargon for swelling. Two serious complications are known as HAPE and HACE: High Altitude Pulmonary Edema and High Altitude Cerebral Edema ­swelling of tissues in the lungs and brain respectively. HAPE has occurred at altitudes from 8000 feet and HACE from 10,000 feet, although both are less unusual at higher altitudes.

HAPE is caused by fluid from tiny blood vessels leaking into air sacs in the lungs, and affects perhaps 2% of those at altitude, usually people who already have some AMS symptoms. Cold, exercise and dehydration all increase the risk of HAPE. So does gender: men are 5-6 times more likely to be affected than women, and children are more at risk than adults. (Children under 10 years are not allowed above 2700 m (9000 feet) on Kilimanjaro.) Around 1 in 10 HAPE cases will die unless promptly diagnosed and treated by immediate descent, oxygen and suitable drugs.

The HAPE sufferer looks ill and

• has extreme difficulty in breathing
• is very weak, unable to sustain any exercise
• has a rapid pulse
• may have a fever
• may have bluish-looking lips and fingernail-beds; this is not unusual at altitude, but, if pronounced, is serious
• may have a cough; if any sputum is pink, frothy or contains blood, the case is serious.

HACE is rarer than HAPE, and results from swelling of the blood vessels in the brain: with no room for expansion, pressure builds up and causes ataxia, extreme lack of energy, incoherence, hallucinations or numbness, followed by coma. HACE may be accompanied by HAPE. Unless treated promptly ­by immediate descent, oxygen and suitable drugs - HACE can be fatal.

Less serious side-effects of altitude include high altitude edema (swelling of hands, face and ankles) which is twice as common in women. Remove any tight-fitting jewellery before going to altitude. High altitude syncope (fainting) can affect some people who stand up immediately after eating, but they often recover and have no further problems. Some people become prone to nosebleeds; these can be inconvenient but are not serious. Most folk make more intestinal gas at altitude, which can be a harmless source of amusement.

Contact lens wearers may find their lenses become unbearably painful at extreme altitude, and should take spectacles as an alternative. Snow blindness is a troublesome condition that can involve headaches, double vision and acutely painful eyes; choose good quality sunglasses that block at least 99% of the ultraviolet rays and either wrap around or have sidepieces

How can you tell if AMS will affect you?

Taking an AMS susceptibility test at The Altitude Centre will help predict your chances of reaching the top in good health. There is also good evidence that things you cannot change, such as age and gender, affect your chances, although doctors cannot explain why. Females are less likely to experience AMS than males. At moderate altitude, young people are more likely to suffer AMS than their elders: the risk decreases with age in an almost straight line.