Arterial blood gas tension changes at the start of exercise in chronic obstructive pulmonary disease.
In a previously reported study of a group of normal subjects, large decreases in arterial O2 tension (PaO2) of as much as 37 mm Hg were measured during the first 90 sec of slow stair-climbing exercise (chosen as a common daily exertion). This study reports the changes in PaO2, arterial CO2 tension (PaCO2), and ventilation in 7 patients with chronic obstructive pulmonary disease and resting hypoxemia during the first 90 sec of similar exercise. The patient group showed significantly smaller unsteady-state decreases in PaO2 starting from a smaller resting value (patient group, 72 +/- 2.6 mm Hg, mean +/- SE; normal group, 92 +/- mm Hg; P less than 0.001) and decreasing to a similar smallest value (patient group, 58 +/- 3.8 mm Hg; normal group, 65 +/- 3.4 Hg; P greater than 0.05). PaCO2 tended to oscillate around the resting value in both the patient group and the normal group, and the rates of increase in ventilation in the 2 groups were similar. The physiologic processes that could limit the unsteady-state decrease in PaCO2 in the patient group are analyzed, the analysis suggesting that a slower rate of increase in tissue consumption of O2 is most likely to account for the smaller decrease in PaO2.
D000328:Adult; D000368:Aged; D002245:Carbon Dioxide / Q000097:blood*; D003201:Computers; D005260:Female; D006801:Humans; D008173:Lung Diseases, Obstructive / Q000097:blood / Q000503:physiopathology*; D008297:Male; D008433:Mathematics; D008875:Middle Aged; D010100:Oxygen / Q000097:blood*; D010313:Partial Pressure; D005082:Physical Exertion; D012119:Respiration; D013997:Time Factors
D002245:Carbon Dioxide; D010100:Oxygen