Changes in lung volumes on acute exposure to high altitude

The purpose of this study was to examine the effect of acute exposure to high altitude on lung volumes. Ten subjects were studied. Sea level control values were obtained for the following lung volumes using a modified single breath nitrogen test; total lung capacity (TLC), vital capacity (VC), residual volume (RV), closing volume (CV, defined as phase IV), closing capacity (CC, defined as CV + RV) and 'open volume' (OV, defined as VC-CV). The subjects were then transported by car to the summit of White Mountain Peak (14,264 ft). The duration of stay at the summit was 5 days. The lung volumes noted above were measured daily in each subject. All volumes were corrected to BTPS conditions. In all subjects, a significant decrease in TLC, VC and OV was found but no significant change in RV, CV or CC throughout the stay at altitude as compared to the sea level control values. These findings suggest that the decrease found in TLC was accompanied by a complementary increase in thoracic tissue volume and therefore in thoracic blood and/or extravascular volume. The finding that CV did not increase suggests that peribronchiolar cuffing was not an appreciable consequence of the increased thoracic fluid volume. It is concluded that the increase in thoracic tissue volume was due to an increase in the intravascular fluid compartment.