Light R B
Department of Medicine, University of Manitoba, Winnipeg, Canada.
J Appl Physiol (1985). 1988 Jun;64(6):2490-5. doi: 10.1152/jappl.1988.64.6.2490.
To test the hypothesis that lung affected by acute bacterial pneumonia consumes significant amounts of O2, whole-body O2 consumption (VO2) was measured simultaneously by collection of expired gas (VO2exp) and by the Fick principle (VO2Fick) in five dogs with acute experimental pneumococcal pneumonia and in five uninfected controls. This approach is based on the premise that VO2Fick will not detect lung VO2, whereas the expired gas measurement represents the true whole-body VO2, including the lung. In controls VO2 exp averaged 110 +/- 20 ml/min (4.78 +/- 0.78 ml.min-1.kg-1), and VO2Fick was nearly identical at 114 +/- 21 ml/min (4.96 +/- 0.79 ml.min-1.kg-1). The VO2Fick in the pneumonia group was 127 ml/min, similar to both control group values when indexed for body weight (4.91 +/- 1.17 ml.min-1.kg-1). VO2exp, however, was 146 +/- 46 ml/min (5.74 +/- 1.57 ml.min-1.kg-1), exceeding VO2Fick by an average of 20 +/- 9 ml/min (P less than 0.01). This between-method difference of 20 +/- 9 ml/min (or 24 ml/min if the difference in the control group is assumed to apply to the pneumonia group) amounted to 13-15% of whole-body VO2 and can be attributed to VO2 in the lung, presumably by cells involved in the acute inflammatory response. Implications include the potential for significant underestimate of whole-body VO2 by the Fick method when used in the presence of lung inflammation and overestimate of blood flow to shunting or low ventilation-perfusion ratio lung units by the O2 method of measuring venous admixture-like perfusion. This observation may also explain the disproportionate hypoxemia sometimes seen in patients with severe pneumonia.
为验证急性细菌性肺炎所致肺部消耗大量氧气这一假说，我们通过收集呼出气体（VO2exp）和运用菲克原理（VO2Fick），对5只患有急性实验性肺炎球菌肺炎的犬以及5只未感染的对照犬同时进行了全身氧气消耗（VO2）的测量。该方法基于这样一个前提：VO2Fick无法检测到肺部的VO2，而呼出气体测量代表的是包括肺部在内的真实全身VO2。在对照组中，VO2exp平均为110±20 ml/分钟（4.78±0.78 ml·min-1·kg-1），VO2Fick与之相近，为114±21 ml/分钟（4.96±0.79 ml·min-1·kg-1）。肺炎组的VO2Fick为127 ml/分钟，按体重指数计算与对照组的两个值相似（4.91±1.17 ml·min-1·kg-1）。然而，VO2exp为146±46 ml/分钟（5.74±1.57 ml·min-1·kg-1），平均比VO2Fick高出20±9 ml/分钟（P＜0.01）。这两种方法之间20±9 ml/分钟的差异（如果假设对照组的差异适用于肺炎组，则为24 ml/分钟）占全身VO2的13 - 15%，可归因于肺部的VO2，可能是由参与急性炎症反应的细胞所致。这意味着，在存在肺部炎症时，使用菲克方法可能会显著低估全身VO2，而通过测量类似静脉混合样灌注的氧气方法可能会高估分流或低通气 - 灌注比肺单位的血流。这一观察结果也可能解释了重症肺炎患者有时出现的不成比例的低氧血症。
