慢性阻塞性肺疾病患者运动高峰时肺内气体交换对运动能力的影响

Effect of gas exchange at maximal intensity on exercise capacity in patients with chronic obstructive pulmonary disease

目的探讨COPD患者在运动高峰时肺内气体交换对最大运动能力的影响。方法对42例男性稳定期COPD患者及26例健康男性进行功率递增至症状自限的踏车运动，同步实时测定摄氧量和二氧化碳产生量，在运动高峰时抽取桡动脉血，测定并计算PaO2、PaCO2、死腔容积与潮气容积比值（VD／VT）和P（A-a）O2.分别对两组资料进行正态性检验，符合正态分布的资料以x^-±s表示，两组间比较采用独立样本t检验，最大摄氧量与运动高峰时的血气参数进行相关因素分析。结果COPD组的最大摄氧量[（16±4）ml·kg^-1·min^-1]明显低于对照组[（19±6）ml·kg^-1·min^-1]；PaCO2[（43±3）mmHg，1mmHg=0．133kPa]、VD／VT（0．35±0．11）和P（A-a）O2[（33±11）mmHg]均明显高于对照组[（40±5）mmHg、0．27±0．08和（15±7）mmHg]；最大摄氧量与VD／VT呈显著负相关（r=-0．734，P〈0．01）。结论VD／VT增加导致通气效率降低，这是引起COPD患者运动能力减低的一个重要原因。

Objective To investigate the effect of gas exchange at maximal intensity on exercise capacity in patients with chronic obstructive pulmonary disease （COPD）. Methods Forty-two male patients with COPD and 26 normal subjects performed incremental exercise test on cycle ergometer. Oxygen uptake and carbon dioxide output were measured continuously on the breath-by-breath mode. Arterial blood samples were drawn at maximal exercise. PaO2, PaCO2, the actual dead space/tidal volume ratios （ VD/VT ） and the alveolar-arterial PaO2 difference [ P（A-a） O2 ] were measured and calculated. Comparisons between the two groups were performed using independent samples t test. Linear regression analyses were made between maximal oxygen uptake （ V^· o2max ） and blood gas variables. Results V^· o2max in patients with COPD [ （ 16 ±4）ml·kg^-1·min^-1] was significantly lower than in normal subjects [（19 ±6）ml·kg^-1·min^-1]. P（A-a）O2, VD/VT and PaCO2 were greater in patients [ （43 ±3） mm Hg, 1 mm Hg =0. 133 kPa, 0. 35 ±0.11, （33±11） mm Hg] than in normal subjects at peak exercise [（40 ±5） mm Hg, 0.27 ±0.08, （15 ±7） mm Hg].V^· o2max correlated strongly with VD/VT at peak exercise in patients （r = -0. 734,P 〈 0.01 ）. Condusion The increase in VD/VT inducing ventilatory inefficiency during exercise is one of the important causes for decreased exercise capacity in patients with COPD.