MAN'S RESPIRATORY RESPONSE DURING AND AFTER ACCLIMATIZATION TO HIGH ALTITUDE

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Abstract
With the aid of an O1-CO2 diagram, data are presented which allow one to predict the alveolar O2 and CO2 composition as well as the relative alveolar ventilation when man is exposed acutely to any altitude; during the process of respiratory acclimatization at any altitude; when acclimatization is complete; and during the process of reacclimatization to a lower altitude. Data obtained from acclimatized man suggests that the threshhold for increased ventilation is near an alveolar pO2 of 100 mm. Hg, while during acute exposure the threshhold is near pO2 of 50-60 mm. Hg. The significance of this difference is discussed. After respiratory acclimatization to 9500 ft. the respiratory system becomes more sensitive to CO2. This response was tested by breathing various CO2 mixtures and analyzing the alveolar air after breath holding. Data are presented which show the reduction of breath-holding time during acclimatization to various altitudes. The various findings emphasize that a large part of the respiratory acclimatization to high altitudes is an adaptation to a lowered CO2 tension.