[Characteristics of exercise ventilation and gas exchange in obese and extremely obese patients]

Objective: To evaluate the characteristics of exercise ventilation and gas exchange in obese and extremely obese patients by Cardiopulmonary exercise test (CPX). Methods: Restrospective anal-ysis of subjects who underwent CPET in Shengjing Hospital of China Medical University from June 2014 to June 2017. A total of 74 subjects were enrolled. According to the body mass index (BMI), 74 subjects were divided into control group(18.5 kg/m(2)≤BMI<23.9 kg/m(2)) (n=21), obese group (28.0 kg/m(2)≤BMI<40.0 kg/m(2)) (n=30) and extremely obese group(BMI≥40.0 kg/m(2))(n=23), respectively. V(O2max), V(O2max)/kg, anaerobic thresh-old(AT), oxygen pulse(V(O2)/HR), breath reserve(BR), inhale time (VTin), expiratory time(VTex) and ventilato-ry equivalent for CO(2)(EqCO(2))were measured by CPX and compared by using one-way ANOVA. Results: Compared to the control group (1 620±400) L/min, the maximal oxygen uptake(V(O2max)) in obese group(1 905±592) L/min and extremely obese group (2 131.09±541.86) L/min were significance higher (F=5.14, P<0.01). The V(O2max)/kg in obese group (19±5) L·min(-1)·kg(-1) and extremely obese groups (16±4) L·min(-1)·kg(-1) were sig-nificant lower than those in control group(27±5)L·min(-1)·kg(-1) (F=35.37,P<0.01). Compared to the control group (9.3±1.4)L·min(-1)·W(-1), the change of oxygen uptake required under certain exercise load (ΔV(O2)/ΔWR) in obese group(9.0±1.7) L·min(-1)·W(-1)and extremely obese group (8.7±2.2) L·min(-1)·W(-1) were no significant difference (F=0.67,P=0.51). The AT in obese group (1 114±391) L/min and extremely obese group (1 348±349) L/min were significant higher than those in control group (832±223) L/min (F=12.85,P<0.01). Com-pared to the control group(10±4) L·min(-1)·b(-1), V(O2)/HR in obese group (12±3) L·min(-1)·b(-1) and extremely obese group(14±3) L·min·b(-1) were significance higher (F=8.16, P<0.01). No significant difference was found between the three groups in BR, VTin, VTex and EqCO(2). Conclusion: obese and extremely obese individu-als have a decreased ablity to exercise when the body requires anaerobic metabolism to provide energy. As exercise power increases, the heart oxygen consumption per stroke and the amount of volume and oxygen re-quired for gax exchange does increase.