Recovery of gas exchange variables and heart rate after maximal exercise in COPD

Studies of the limited exercise capacity in patients with COPD have not assessed the recovery phase, although the phenomenon of increased oxygen uptake after exercise has been thoroughly investigated in normal subjects. Therefore, we compared the recovery of gas exchange variables and HR after maximal cycle ergometry in 16 patients with varying severities of airflow obstruction and ten aged control subjects. Aerobic capacity was reduced in the patients with COPD, and the rates of recovery of VE, VO2, VCO2, excess VCO2, and HR were all significantly slower in the patients with COPD than in the controls. When expressed as the half-time for recovery, patients with COPD had values which were approximately twice that of control subjects for gas exchange and HR. The extent of recovery was similar in patients and controls. We conclude that in patients with COPD, postexercise relative hyperpnea and hypermetabolism are significantly prolonged. In addition, impaired elimination of increased body stores of carbon dioxide may contribute to impaired adjustment to acid-base disorders in these patients.