Weg J G
Department of Internal Medicine, University of Michigan Medical Center, Ann Arbor 48109.
Crit Care Med. 1991 May;19(5):650-7. doi: 10.1097/00003246-199105000-00011.
To evaluate the evidence that oxygen consumption (VO2) is pathologically dependent on oxygen delivery (DO2).
Studies published since 1972 with their relevant bibliographies and computerized search of MEDLINE.
All clinical papers reporting the relationship of: VO2 to DO2 in the adult respiratory distress syndrome (ARDS), sepsis, other critically ill patients, and normal individuals; cardiac output determined by measured VO2 to calculated VO2 from the arterial-mixed venous oxygen difference; blood lactate to DO2; and selected basic science studies.
Study quality was assessed and all pertinent data were summarized. RESULTS OF DATA EXTRACTION: Normal individuals display physiologic dependence of VO2 at very low levels of DO2 (330 mL/min.m2). Pathologic dependence of VO2 on DO2 entails two concepts: a) VO2 varies directly with DO2 over a wide range of DO2 and b) of particular import, tissue oxygen extraction is compromised. This pathologic supply dependence was initially identified in patients with ARDS; subsequently, it has been demonstrated in patients with sepsis and in a variety of other critically ill individuals. There are substantial, but not uniform, data documenting this dependence of VO2 on DO2 in ARDS. In some studies, this relationship correlates best with increased lactate concentrations. However, increased blood lactate concentrations do not accurately track other evidence of tissue hypoxia. Some researchers have attributed the finding of this supply dependency to artifact, when VO2 is determined by the arterial-mixed venous oxygen difference. However, when these methods are compared, the correlation is excellent. Others have raised the concern that appreciable changes in VO2, even over short periods of time, may result in physiologic increases in DO2. However, when "control" groups have been contemporaneously compared with patients with ARDS using the same methodology, they have not shown supply dependency. Interwoven throughout the studies reviewed is overwhelming and uniform evidence that both mixed venous oxygen tension (PVO2) and mixed venous oxygen content (CVO2) correlate poorly with cardiac output, DO2, or VO2. The inconsistencies in identifying pathologic DO2 dependency may well reflect the unknown variables that exist in patients with ARDS, perhaps better labeled, multiple organ system failure.
Pathologic dependence of VO2 on DO2, especially the inability to increase tissue oxygen extraction, is present in most patients with ARDS and many other critically ill individuals. PVO2 and CVO2 are both unreliable indicators of cardiac output, DO2, or VO2.
评估氧耗量（VO2）在病理状态下依赖于氧输送（DO2）的证据。
1972年以来发表的研究及其相关参考文献，并通过计算机检索MEDLINE。
所有报告以下关系的临床论文：成人呼吸窘迫综合征（ARDS）、脓毒症、其他危重病患者及正常个体中VO2与DO2的关系；通过实测VO2与根据动脉-混合静脉血氧差计算的VO2来确定心输出量；血乳酸与DO2的关系；以及部分基础科学研究。
评估研究质量并总结所有相关数据。资料提取结果：正常个体在极低水平的DO2（330 ml/min·m2）时显示VO2的生理依赖性。VO2对DO2的病理依赖性涉及两个概念：a）在较宽的DO2范围内，VO2与DO2直接相关；b）特别重要的是，组织氧摄取受损。这种病理供应依赖性最初在ARDS患者中被发现；随后，在脓毒症患者及其他多种危重病个体中也得到证实。有大量但并不一致的数据记录了ARDS中VO2对DO2的这种依赖性。在一些研究中，这种关系与乳酸浓度升高的相关性最佳。然而，血乳酸浓度升高并不能准确反映组织缺氧的其他证据。一些研究人员将这种供应依赖性的发现归因于人为因素，即当通过动脉-混合静脉血氧差来测定VO2时。然而，当比较这些方法时，相关性非常好。其他人则担心，即使在短时间内VO2发生明显变化，也可能导致DO2的生理性增加。然而，当使用相同方法将“对照组”与ARDS患者同时进行比较时，对照组并未显示出供应依赖性。在所审查的研究中贯穿始终的是压倒性的一致证据，即混合静脉血氧分压（PVO2）和混合静脉血氧含量（CVO2）与心输出量、DO2或VO2的相关性都很差。在确定病理性DO2依赖性方面的不一致很可能反映了ARDS患者中存在的未知变量，或许更确切地说是多器官系统功能衰竭。
VO2对DO2的病理依赖性，尤其是无法增加组织氧摄取，在大多数ARDS患者及许多其他危重病个体中都存在。PVO2和CVO2都是心输出量、DO2或VO2的不可靠指标。
