title: The effect of exercise on pulmonary gas exchange in patients with severe chronic obstructive pulmonary disease.
abstract: The effect of low level, steady-state exercise on pulmonary gas exchange was studied in 7 patients with severe chronic obstructive pulmonary disease and pulmonary hypertension. Exercise led to a significant fall in the arterial PO2 from 76 +/- 10 to 63 +/- 8 mm Hg, a rise in the arterial PCO2 from 56 +/- 6 to 62 +/- 8 mm Hg, and a fall in the mixed venous PO2 from 38 +/- 2 to 32 +/- 2 mm Hg. There was, however, no significant change in the degree of ventilation-perfusion inequality as quantified by the multiple inert gas technique and no evidence that impaired O2 diffusion was playing a role in the increased hypoxemia. We conclude that the worsening hypoxemia with exercise in patients with severe COPD is due to an inadequate ventilatory response (leading to a rise in arterial PCO2) and the impact of a decreased mixed venous PO2 on the end-capillary PO2 of low VA/Q lung units and shunt.
mesh_terms: D002245:Carbon Dioxide / Q000097:blood; D005080:Exercise Test; D006801:Humans; D006976:Hypertension, Pulmonary / Q000503:physiopathology; D008173:Lung Diseases, Obstructive / Q000503:physiopathology*; D010100:Oxygen / Q000097:blood; D010313:Partial Pressure; D005082:Physical Exertion; D011659:Pulmonary Gas Exchange; D012146:Rest; D014692:Ventilation-Perfusion Ratio
chemical_list: D002245:Carbon Dioxide; D010100:Oxygen