[Evaluation of cardiopulmonary function in Japanese Himalayan climbers to the Himalayas underin a hypobaric hypoxic chamber].

The Tokai University and Tibet University Scientific Friendship Expedition 2001 succeeded in reaching the summit of Kula Kangri (7,538 m) in the Himalrayas without supplementary O2 in May, 2001. Before this expedition, the cardiopulmonary function of all members was evaluated using a hypobaric hypoxic chamber in which the barometric pressure was gradually lowered to a simulated altitude of 6000 m. Whenever a member's PaO2 was lower than 40 torr during the experiment, supplementary O2 was given. The results were divided into two groups, Group A and Group B, according to whether supplementary O2 was used. Group A subjects did not need O2 even at an altitude of 6,000 m, whereas Group B subjects did when they reached an altitude of 5,000 m. Seven the eight Group A members had climbed mountains over 4,000 m several times, whereas twelve out of the thirteen members of Group B had no mountaineering experience. The mean PaO2 and PaCO2 of Group A at 6000 m were 41.9 torr and 31.9 torr, respectively, while those of Group B at 5000 m were 35.8 torr and 35.9 torr. There was a significant difference in the degree of hyperventilation between Group A and Group B. No difference was observed between the two groups in systolic and diastolic arterial blood pressure, but the heart rate in Group B increased significantly under hypoxia. These results suggest that the experience of climbing mountains over 4000 m may lead to significant differences in cardiopulmonary function under hypoxia.