Effect of breathing pattern and ventilatory efficiency on exercise performance in chronic obstructive pulmonary disease

Objective: To evaluate the effects of breathing pattern and respiratory efficiency on exercise capacity in patients with chronic obstructive pulmonary disease (COPD). Methods:Maximal cardiopulmonary exercise testing (CPXT) was performed in 32 patients with COPD and 29 age-and sex-matched control subjects. O_ 2 -uptake ( V· O_ 2 ),CO_ 2 -output ( V· CO_ 2 ),work rate (WR),anaerobic threshold,minute ventilation ( V· _ E ),ventilatory efficiency ( V· _ E / V· CO_ 2 ),tidal volume (V_ T ),respiratory frequency (f_ R ),and other parameters related with breathing pattern were measured used by CPXT both at rest and peak of exercise in each subject. Results: At peak of exercise,maximal V· O_ 2 was significantly decreased in COPD ( P 0.001). Compared with control subjects,COPD had longer expiratory time (1.21±0.04s vs 1.04± 0.03s,P 0.01),lower V· _ E (36.1±1.8L/min vs 53.0±2.5L/min,P 0.001),maximal V_ T (1.28±0.05L vs 1.71±0.08L,P 0.001),and the ratio of T_ I to total respiratory time (0.44±0.01 vs 0.47±0.01, P 0.001). At peak of exercise,V· _ E / V· CO_ 2 was significantly higherinCOPDgroupthanthatincontrols(32.4±1.4 vs 27.3±1.0,P 0.01). Conclusion: The changed breathing pattern and lower respiratory efficiency were important factors in damaged exercise performance in COPD.