OPERATION EVEREST-II - SPIROMETRIC AND RADIOGRAPHIC CHANGES IN ACCLIMATIZED HUMANS AT SIMULATED HIGH-ALTITUDES

We report spirometry and radiographic data on eight normal male human subjects during prolonged graded altitude exposure to as high as 8,848 m above sea level in a hypobaric chamber. We found a significant and progressive drop in FVC by 14 +/- 3% over 40 days, which resolved slow ly during the first 48 h after descent. With altitude, midrange forced expiratory flow (FEF25-75) increased by 82 +/- 3%, probably because o f reduced air density. FEV1, however, did not change. Chest radiograph s on subjects taken 2 h after descent to sea level showed a pattern of pulmonary artery enlargement and interstitial edema. These data sugge st that increased pulmonary blood volume and edema may be causes of th e restricted pulmonary function pattern.