The thickness of the alveolar capillary wall in the human lung at high and low altitude.

An ultrastructural study of lung biopsy specimens from an adult mestizo highlander from La Paz (3800 m) and three lowlanders from London showed no significant difference in the thickness of the alveolar capillary wall, the thickness in the highlander being 0.65 micron and the range in the lowlanders being 0.57-0.69 micron. The thickness of the blood-air barrier in a mestizo girl of 4 years born and living in La Paz was 0.47 micron. These findings suggest that the alveolar capillary wall in the acclimatized highlander does not differ in thickness from the lowlander. This contrasts with our previous findings in native high altitude guinea pigs which indicate that the alveolar capillary wall is thinner in such indigenous mountain species which are adapted genetically rather than acclimatized to hypobaric hypoxia.