OBJECTIVE To investigate the change of alveolar-arterial partial pressure of oxygen (PO2) difference [P (A-a) O2)] at rest and during exercise in patients with chronic obstructive pulmonary disease (COPD). METHODS Cardiopulmonary exercise testing was performed in 47 COPD male patients aged (66 +/- 8) at stable stage to measure the oxygen uptake (VO2) and carbon dioxide output (VCO2) continuously in a breath-by-breath mode. Arterial blood samples were drawn both at rest and during maximal exercise. P(A-a) O2 is computed by the equation: PAO2-PaO2. RESULTS The PaO2 level during exercise was (89 +/- 14) mm Hg, a little bit, however, not significantly, lower than that at rest [(92 +/- 9) mm Hg, P = 0.506]. The PaCO2 during exercise was 43 +/- 3 mm Hg, significantly higher than that at rest (41 +/- 4 mm Hg, P = 0.003). The patients were divided into two groups according to lung diffusing capacity for carbon monoxide (DLco). There was a significant increase in P(A-a) O2 from (16 +/- 8) mm Hg at rest to (42 +/- 9) mm Hg during maximal exercise in the DLco < 80% group (P = 0.005); however, in the DLco >80% group the P(A-a) O2 level during maximal exercise was (26 +/- 6) mm Hg, not significantly different from that at rest [(20 +/- 6) mm Hg, P = 0.106]. The P(A-a)O2 level of the DLco <80% group during maximal exercise was (42 +/- 9) mm Hg, significantly higher than that at rest [(16 +/- 8) mm Hg, P = 0.005]. The P(A-a)O2 was significantly negatively correlated with the forced vital capacity (r= -0.581, P = 0.037) and DLco (r = -0.671, P = 0.012). CONCLUSION The increase in P (A-a) O2 during exercise in the COPD patients is mainly due to the limited diffusing capacity of the lung.

中文翻译：

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慢性阻塞性肺疾病患者静息和最大运动量时肺泡-动脉分压的氧差异测量

目的探讨慢性阻塞性肺疾病（COPD）患者休息和运动过程中肺动脉氧分压（PO2）[P（Aa）O2]的变化。方法对47名年龄在（66 +/- 8）岁的COPD男性患者进行了稳定的心肺运动测试，以逐呼吸的方式连续测量其摄氧量（VO2）和二氧化碳输出量（VCO2）。在静止和最大运动量时抽取动脉血样品。P（Aa）O2由以下公式计算：PAO2-PaO2。结果运动过程中的PaO2水平为（89 +/- 14）mm Hg，但比静止时稍低（[92 +/- 9）mm Hg，P = 0.506]。运动期间的PaCO2为43 +/- 3 mm Hg，显着高于休息时的PaCO2（41 +/- 4 mm Hg，P = 0.003）。根据肺对一氧化碳的扩散能力将患者分为两组。在DLco <80％组中，最大运动期间P（Aa）O2从静止时的（16 +/- 8）mm Hg显着增加到（42 +/- 9）mm Hg（P = 0.005）；但是，在DLco> 80％组中，最大运动期间的P（Aa）O2水平为（26 +/- 6）mm Hg，与静止时[（20 +/- 6）mm Hg，P = 0.106]。在最大运动中，DLco <80％组的P（Aa）O2水平为（42 +/- 9）mm Hg，显着高于休息时[（16 +/- 8）mm Hg，P = 0.005]。P（Aa）O2与强迫肺活量（r = -0.581，P = 0.037）和DLco（r = -0.671，P = 0.012）显着负相关。