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It was like I was very drunk. I couldn’t walk without stumbling, and completely lost the ability to think or speak. It was a really strange feeling. I’d have some word in my mind, but I couldn’t figure out how to bring it to my lips.
Dale Kruse, mountain climber, describing the effects of high-altitude cerebral oedema when climbing Mt Everest
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As travel continues to get easier and cheaper, altitude sojourns for recreation or (hypoxic) training continue to grow in popularity. Alpinists cross peaks from their bucket lists; sporting teams and individual athletes look for higher ground to gain a competitive advantage; and active travellers enjoy spectacular recreation. Whether it be mountaineering in the Swiss Alps or training in high-altitude destinations like Flagstaff, Arizona, or in a simulated altitude tent closer to home, altitude exposure is now part of the mainstream sport and exercise medicine world.
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The underlying principle of altitude training is that by exposing an individual to an environment that is low in available oxygen, the body will adapt and improve its efficiency at transporting and using limited oxygen. Endurance athletes in particular take advantage of exercising at high altitude to enhance performance once returning to sea level, or to acclimatise to competition at altitude. They employ a number of different altitude training strategies, such as ‘live high, train high’ or ‘live high, train low’, as discussed in this chapter.
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Despite all the benefits of altitude training, exposing the body to extreme stress comes with risks. Clinicians must be aware of the potential dangers for every patient and help to mitigate the risk of altitude illness. The term ‘high-altitude illness’ refers to all conditions that can occur as a result of exposure to altitude, including acute mountain sickness, high-altitude pulmonary oedema and high-altitude cerebral oedema.
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Reflecting the two sides of the altitude coin—risk and potential benefit—the chapter is split into two parts:
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MEDICAL CONCERNS AT ALTITUDE
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High-altitude illness
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High-altitude illness usually occurs at altitudes above 3000 m (10 000 ft) and can cause significant morbidity. The life-threatening manifestations of high-altitude illness, high-altitude cerebral oedema and high-altitude pulmonary oedema occur in 0.1–4.0% of visitors to altitude.1, 2 A larger proportion of travellers experience acute mountain sickness, which typically presents as headache, nausea, vomiting, dizziness, fatigue and insomnia. Although these milder symptoms are not life threatening, they can be severe enough to interfere with trip participation and enjoyment. Fortunately, altitude illness is preventable and proper pre-trip planning can reduce morbidity and mortality.
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Acute mountain sickness
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Acute mountain sickness can occur when a person who is accustomed to being at a low altitude ascends to a higher altitude. It is the most common type of high-altitude illness ...