The Death Zone on Mount Everest begins at around 8,000 metres. Low oxygen there can trigger High Altitude Cerebral Edema (HACE). Symptoms include confusion, hallucinations, loss of coordination and eventually coma. Climbers can develop High Altitude Pulmonary Edema (HAPE), causing severe breathlessness and coughing. Muscle power drops sharply and lack of oxygen may impair judgment severely.