Abstract

Acute mountain sickness (AMS) is a syndrome of nausea, headache, lethargy and anorexia which often affects even fit travellers to high altitudes. Sleep is fitful and may be disturbed by dreams and periodic breathing or apnoea. The condition usually resolves within three days of arriving at altitude, but occasionally it leads to life-threatening cerebral or pulmonary oedema. AMS is commonest above 3,000 metres (about 10,000 feet) although a mild form may occur at lower altitudes particularly if ascent has been rapid. About 4% of visitors to Pheriche in Nepal at 4,243m suffered tachypnoea and cyanosis, or headache, ataxia and disorientations; over 50% had milder symptoms.¹