[Acute altitude sickness and ventilatory function in subjects intermittently exposed to hypobaric hypoxia]

Aiming to assess the magnitude of acute mountain sickness symptoms and ventilatory function in subjects intermittently exposed to hypobaric hypoxia, we studied 48 healthy men aged 32.6 +/- 8.2 years old who worked in a gold mine at a altitude of 4600 m, using a schedule of 8-12 days of work at the mine followed by 4 days of rest at the sea level. Studies were performed at the sea level (A), during the first two days of ascension (B) and after three or four days of stay at 4600 m (C). Mountain sickness symptoms were evaluated with a questionnaire devised in the 1991 International Hypoxia Symposium and respiratory function was assessed with a Collins Eagle II respirometer, following American Thoracic Society recommendations. Subjects reported mild to moderate symptoms during the first 24 hours of ascending (mean score of 6.4 +/- 3.1 for a maximum of 15). Forced vital capacity fell significantly in period B and returned to normal in period C and forced expiratory volume in 1 s did not change in any period. However, maximal expiratory flow and maximal midexpiratory flow rate significantly increased and remained elevated during the four days stay at the mine. No correlation was found between acute mountain sickness symptoms and changes in ventilatory function.