Abstract
Summary and Conclusions
1. Apparent variations in pulmonary vital capacity are found from day to day and from season to season. When corrections are made for temperature and atmospheric pressure, these variations disappear. 2. True vital capacity diminishes at moderate altitudes, changes appearing even at 3000 feet. The various factors to which these changes have been attributed by different observers were absent in our experiments. Diminished vital capacity at altitudes is believed to be due to dilatation of lung capillaries following the partial loss of external (atmospheric) support, with consequent diminution of air space. Such an increase of blood in the lungs may be a factor in the favorable effect of moderate altitudes on certain forms of pulmonary tuberculosis.
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