Bracco D, Chioléro R, Pasche O, Revelly J P
Institute of Physiology, University of Lausanne, Switzerland.
Chest. 1995 May;107(5):1406-10. doi: 10.1378/chest.107.5.1406.
This study was performed on patients after coronary artery bypass surgery, and in healthy volunteers to assess discrepant oxygen consumption (VO2) measurement between indirect calorimetry and Fick methods. Further evaluations were performed to point out the technical failure.
In this prospective study, the VO2 was assessed in the patients using a commercial indirect calorimeter and the reverse Fick method. This calorimeter does not directly measure gas flow, but it assumes a constant preset flow. Bench testing of the calorimeter was performed in spontaneous and respirator mode using a reference calorimeter in healthy volunteers.
An important overestimation of VO2 and carbon dioxide production (VCO2) of approximately 30% was found in both groups. The actual flow was lower than the preprogrammed value. This lead to spuriously high fractions of carbon dioxide and low fraction of oxygen. VCO2 and VO2, calculated with the overestimated gas flow value were overestimated, while respiratory quotient remained unchanged. Technical check-up revealed leaks in the mixing chamber and in the sampling lines.
Indirect calorimetry is a useful clinical tool, but the investigator has to be very attentive to all potentially interfering factors and hazards.
本研究对冠状动脉搭桥手术后的患者及健康志愿者进行，以评估间接测热法与菲克法在氧耗量（VO₂）测量上的差异。还进行了进一步评估以指出技术故障。
在这项前瞻性研究中，使用商用间接热量计和反向菲克法对患者的VO₂进行评估。该热量计不直接测量气体流量，而是假定为恒定的预设流量。在健康志愿者中，使用参考热量计在自发呼吸和机械通气模式下对热量计进行台架测试。
两组中均发现VO₂和二氧化碳产生量（VCO₂）被高估了约30%。实际流量低于预编程值。这导致二氧化碳比例虚高而氧比例偏低。用高估的气体流量值计算出的VCO₂和VO₂被高估，而呼吸商保持不变。技术检查发现混合室和采样管路存在泄漏。
间接测热法是一种有用的临床工具，但研究者必须非常留意所有潜在的干扰因素和风险。
