Early-Phase Recovery of Cardiorespiratory Measurements after Maximal Cardiopulmonary Exercise Testing in Patients with Chronic Obstructive Pulmonary Disease

Abstract

Background. This study investigated respiratory gas exchanges and heart rate (HR) kinetics during early-phase recovery after a maximal cardiopulmonary exercise test (CPET) in patients with chronic obstructive pulmonary disease (COPD) grouped according to airflow limitation. Methods. Thirty control individuals (control group: CG) and 81 COPD patients (45 with “mild” or “moderate” airflow limitation, COPD _I-II, versus 36 with “severe” or “very severe” COPD, COPD _III-IV) performed a maximal CPET. The first 3 min of recovery kinetics was investigated for oxygen uptake ( $\dot{\mathrm{V}}$ O ₂), minute ventilation ( ${\dot{\mathrm{V}}}_{\mathrm{E}}$ ), respiratory equivalence, and HR. The time for $\dot{\mathrm{V}}$ O ₂ to reach 25% (T _1/4 $\dot{\mathrm{V}}$ O ₂) of peak value was also determined and compared. Results. The $\dot{\mathrm{V}}$ O ₂, ${\dot{\mathrm{V}}}_{\mathrm{E}}$ , and HR recovery kinetics were significantly slower in both COPD groups than CG ( p < 0.05). Moreover, COPD _III-IV group had significantly higher $\dot{\mathrm{V}}$ O ₂ and ${\dot{\mathrm{V}}}_{\mathrm{E}}$ during recovery than COPD _I-II group ( p < 0.05). T _1/4 $\dot{\mathrm{V}}$ O ₂ significantly differed between groups ( p < 0.01; 58 ± 18 s in CG, 79 ± 26 s in COPD _I-II group, and 121 ± 34 s in COPD _III-IV) and was significantly correlated with forced expiratory volume in one second in COPD patients ( p < 0.001, r = 0.53) and with peak power output ( p < 0.001, r = 0.59). Conclusion. The COPD groups showed slower kinetics in the early recovery period than CG, and the kinetics varied with severity of airflow obstruction.