Breathing patterns in mountaineers climbing to extreme altitude (7546m)

Background We investigated breathing patterns and oxygenation in mountaineers climbing to extreme altitude to evaluate effects of hypoxemia and acclimatization. Methods In 34 mountaineers (mean age 45y, 7 women) portable recordings of respiratory inductive plethysmography, pulse oximetry and ECG were performed during a climb to the summit of Muztagh Ata, China (7546m). Breath by breath ventilation was analyzed and periodic breathing quantified by spectral analysis. Results Repeated recordings during 2 climbs from 4497-5533m within 5-8 days revealed an increase in oxygen saturation and periodic breathing and a decrease in heart rate (table). During the climb from 6865-7546m hypoxemia was pronounced. Conclusions Mountaineers were able to climb to extreme altitude despite severe hypoxemia. The heart rate reserve was utilized to a greater extent than the ventilatory reserve. With acclimatization, periodic breathing increased despite a higher oxygen saturation, consistent with a persistently high ventilatory drive while the heart rate reduction suggested a decrease in sympathetic tone. View this table: Physiologic adaptation during ascent to 7546m