Acute mountain sickness without headache at low altitude

A 45-year-old tourist developed AMS three hours after starting to ski in a glacier skiing-region in Austria. His history was noteworthy for chronic stress, coffee-overuse, chronic sleep-deprivation, and previous AMS, 14 years ago at ∼3000 m and six years ago at ∼5100 m. He occasionally trekked to altitudes of 1500–2500 m without problems. The night before suffering AMS he had slept for four hours at an altitude of 760 m, and had drunk 1 L of coffee in the morning but less during previous days. He did not take any azetazolamide prophylaxis before travelling to the glacier. After a 30-minute drive to the skiing-arena, he took the first cable car and went skiing for three hours without any problems (Table 1). After a strenuous ride off the regular slope he became tired and movements slowed down but recovered during ascent to 2678 m (Table 1). He skied down to 2450 m and although he needed a rest, he ascended to 2656 m. During this ascent at ∼11 h he recognized intense tiredness and progressive impairment of breathing. He developed nausea and had the urgent need to descend to lower altitudes. He skied down to 2450 m with an increasing number of stop-overs. On arrival he was dyspnoeic with a breathing rate of ∼50/ min, panted for air, longed for oxygen, was tachycardious, recognized paresthesias of both hands and feet, and no longer able to recover despite resting. He managed to get on a cable car on his own, with slow motions, and descend to 1979 m. Despite this descent within four minutes and lying flat in the cabin, tachypnoea and tachycardia persisted, he became dizzy and feared he would immediately faint. When arriving at 1979 m he had difficulty leaving the cabin, to stay upright and to move. He was hardly able to lean on his sticks and took every effort not to faint. An employee of the lift-company helped the patient into a cable car and accompanied him on his further descent, during which tachypnoea and tachycardia did not resolve. He asked the employee to call the emergency services to give him oxygen and to transfer him to a hospital on arrival. After delayed arrival of the doctor at the valley station, he measured a blood pressure of 120/60 mmHg, rhythmic tachycardia (116 beats/min) and a breathing rate of 42/min. He interpreted the condition as psychogenic hyperventilation, and vigorously prompted the patient to voluntarily stop tachypnoea and tried to infuse 500 mL of sodium-chloride plus diazepam (10 mg), which the patient vehemently refused. During transport to the hospital, tachypnoea and tachycardia resolved, and on admission auscultation and blood pressure were normal, electrocardiography showed sinus-rhythm (87/min), normal breathing rate, and normal creatine kinase and D-dimer. Blood gas analysis and X-ray of the lung were normal. He was not given oxygen at any time when symptoms evolved. He dismissed himself against medical advice and despite some concern about the incident, went skiing the same day. He ascended to maximally 2000 m during the next two hours, but tolerated the strain with some indisposition and weird feeling. After sufficient sleep, he skied during the whole next day to a maximal altitude of 2074 m, without complaints. Two days after AMS, he went to the same glacier skiing-region, where he had experienced AMS, even to an DECLARATIONS