Breath Holding during the Three Weeks of Sojourn at High Altitude

This study is a part of the work which has been done in purpose of investi· gating the effects of a long term exposure to a lowered barometric pressure in the 1965-1966 Nagoya university scientific and mountaineering expedition to the Andes. Changes in breath holding time, Po, and Poo, of the expired air at the breaking point and alveolar Po, and Pco2, pulmonary ventilation and respiratory frequency were measured in the 14 male subjects during the 22 days of sojourn at an altitude of 4200 m. Breath holding time and Poo, of the expired air at the breaking point and alveolar Pee, became increasingly lower during the two weeks of sojourn. After the 2nd week the breath holding time, P co, level at the breaking point reached the minimum while the alveolar Pco, continued to fall. Pulmo· nary ventilation and respiratory frequency as well as the alveolar Po, increased and reached a ceiling during the third week of sojourn. Those rather quick changes during the first two weeks would indicate an increased sensitivity of the respiratory center to COz stimulus, but the discrepancy between the change in breathh olding time and that in alveolar Pco, after the third week of sojourn was difficult to be interpreted in this paper. An augumented ventilatory response to COz in the inspired air is one of the characteristics of acclimatization to high altitude1J2l, but the mechanism for this augumentation in the subjects acclimatized to high altitude is not yet fully understood. The hypotheses which have been advanced are in referring to 1) the importance of the lowered blo~d buffer capacity3>, 2) an accentuation of the centrogenic drive4> and 3) the presence of an increased sensitivity of the respiratory center to the chemical stimulus of C0z1>5>6>. In the 1965-1966 Nagoya university scientific and mountaineering expedition to the Andes, the authors had an opportunity to measure the response of the respiratory system :tK:!:Bt!%1;:1':' *~ ~' ?,t;T:fltll; :;t :Jl![5 Received for publication, April 22, 1966. 1l Faculty member of Research Institute for Environmental Medicine, Nagoya University. 2> The leader of the 1965-1966, Nagoya University Scientific and Mountaineering Expedition to the Andes. 86 T. NAGASAKA, S. ANDO AND K. TAKAGI in the subjects at an altitude of 4200 m. With rather simple techniques of measuring breath holding time and alveolar gas tension, the authors have been provided to have a conclusion in verifying validity of the hypothesis that the increased sensitivity of the center to C02 would be an important factor in increasing ventilation in the subjects at high altitude. The results of the ex· periment and the outline of the expedition will be described in this paper.