Breathing pattern and gas exchange at cardiopulmonary exercise testing in stable moderate to severe chronic obstructive pulmonary chisease patients with different extent of lung hyperinflation

Abstract

Objective To study the influence of lung hyperinflation on breathing pattern and gas exchange at cardiopulmonary exercise testing (CPET) in stable moderate to severe chronic obstructive pulmonary disease (COPD) patients.Methods Pulmonary function test (PFT) and CPET were tested in 54 patients with stable moderate to severe COPD,and measured the parameters of ventilation,breathing pattern and gas exchange.The stopped reasons at the end of exercise testing were be noted.Patients who had an emphysematous profile with the perccntage of thoracic gas volume predicted value (Vtg％pred)＜150％ and the percentage of diffusing lung capacity for carbon monoxide predicted value (DL.CO％pred)≥80％ (low lung hyperinflation,Group A),versus patients with Vtg％pred≥150％ and DLCO％pred＜80％ (high lung hyperinflation,Group B).Results At rest,there was no significant difference in tidal volume (VT) and breathing frequency between these two groups,at peak exercise,VT and minute volume ((V)E) in Group A were significant higher than Group B (P＜0.001).Between the two groups,tl/tE,VT/tl and VT/tE had significant difference at peak exercise (P＜0.01).The dyspnea of Group B was more severe than Group A (P＜0.001).At peak exercise,the peak load,peak oxygen consumption ((V)O2),the efficiency of gas exchange and peak oxygen pulse (O2 pulse) in Gropu B were lower than Group A (P＜0.05).The reason for stopping exercise was significantly different between the two groups.Peak (V)O2％pred was significant associated with Vtg％pred and DLCO％pred(r=-0.55and 0.68,P＜0.001),peak (V)O2 was significant associated with peak VT (r=0.77,P＜0.001),moreover,peak VT was significant associated with inspiratory capacity (r=0.63,P＜0.001).Conclusions COPD patients who with the higher lung hyperinflation had the less exercise capacity,less ventilation function,reduced efficiency of gas exchange,and worse dyspnea. Key words: Chronic obstructive pulmonary disease; Lung hyperinflation; Cardiopulmonary exercise testing; Breathing pattern; Inspiratory capacity