Effects of two years' intermittent stay at high altitudes on the pulmonary blood volume in man.

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Abstract
Data on the response of the pulmonary blood volume to 2 years'' intermittent stay in 13 subjects stationed at an altitude of 4422 m (14,500 ft) (group A) and in another 13 subjects who camped at this altitude but shuttled daily to 4880 m (16,000 ft) or higher (group B) are given. Average pulmonary blood volumes of both the groups were grossly increased, (A) 463 ml/m2 and (B) 625 ml/m2, as compared with the normal value of 210 m/m2. The relatively greater increase in group B subjects might have been due to their daily shuttle to higher altitudes. The increase in the central blood volume was found to be dependent on the increase in pulmonary blood volume, but response of the latter was found to be independent of the former. It is postulated that the triphasic response, i.e. early increase for the 1st 10 to 15 weeks, normal values from 15th to 38th week, and thereafter significant increase of the pulmonary blood volume, as seen in a few subjects of group B, may represent a homeostasis mechanism between the pulmonary and the extra-pulmonary circuits.