Changes in arterial blood gas tensions during unsteady-state exercise.
Arterial oxygen (Pao2) and carbon dioxide (Paco2) tensions and inspired minute ventilation were measured during the first 2 min of stair-climbing exercise in nine normal subjects. The subjects climbed a staircase at a rate of approximately 9 m vertical height every minute and arterial blood was drawn from an indwelling cannula at 15-s intervals. Large falls in Pao2 from a resting value of 92 +/- 2.0 (mean +/- SE) Torr to a lowest value of 65 +/- 3.4 Torr were recorded in the first 50 s of exercise while Paco2 oscillated around the resting value. Most subjects demonstrated an initial plateau of Pao2 for at least 7 s followed by a rapid fall and subsequent rise toward the resting level after 1 min. The falls in Pao2 measured were larger than those reported for laboratory exercise. The possible reasons for this discrepancy are discussed.
D000328:Adult; D002245:Carbon Dioxide / Q000097:blood*; D002302:Cardiac Output; D005260:Female; D006801:Humans; D008297:Male; D010100:Oxygen / Q000097:blood*; D010101:Oxygen Consumption; D005082:Physical Exertion; D011652:Pulmonary Circulation; D012119:Respiration
D002245:Carbon Dioxide; D010100:Oxygen