Early-Phase Recovery of Cardiorespiratory Measurements after Maximal Cardiopulmonary Exercise Testing in Patients with Chronic Obstructive Pulmonary Disease
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, COPDI-II, versus 36 with "severe" or "very severe" COPD, COPDIII-IV) performed a maximal CPET. The first 3 min of recovery kinetics was investigated for oxygen uptake ([Formula: see text]O2), minute ventilation ([Formula: see text]), respiratory equivalence, and HR. The time for [Formula: see text]O2 to reach 25% (T1/4[Formula: see text]O2) of peak value was also determined and compared. Results. The [Formula: see text]O2, [Formula: see text], and HR recovery kinetics were significantly slower in both COPD groups than CG (p < 0.05). Moreover, COPDIII-IV group had significantly higher [Formula: see text]O2 and [Formula: see text] during recovery than COPDI-II group (p < 0.05). T1/4[Formula: see text]O2 significantly differed between groups (p < 0.01; 58 ± 18 s in CG, 79 ± 26 s in COPDI-II group, and 121 ± 34 s in COPDIII-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.