Ascent to high altitude leads to a number of changes in lung function. We studied 55 subjects at sea level and as they ascended from 2600m to 5300m over 8 to 14 days to investigate the possible time course of these changes. Using a turbine spirometer, previously validated at simulated altitude, subjects recorded their peak expiratory flow (PEF), forced expiratory volume in one second (FEV1) and forced vital capacity (FVC) on arrival at each new attitude and again the next morning. Compared to...