Oxygen Supply Dependency — Fact or Artifact?
Intensive care specialists became interested in this topic following a paper of Danek et al. (1) that appeared 15 years ago. Their observation was that oxygen uptake (VO2) varied directly and linearly with any change in DO2 in ARDS patients. This was not the case in a comparable group of ventilator patients who did not have ARDS. The apparent dependence of VO2 upon DO2 in ARDS patients was seen at relative high levels of DO2, well above those that were thought to be critical. From experiments on anesthetized animals, VO2 was known to remain unchanged over a wide range of DO2, by altering O2 extraction appropriately. When the limit of compensatory changes was reached as DO2 was progressively lowered, VO2 would then change linearly with DO2. The term “physiologic O2 supply dependency” was first introduced by Cain for this phenomenon in contrast to the feature that was strikingly different in ARDS and sepsis patients which was called “pathologic supply dependency” (2).
KeywordsSeptic Shock Oxygen Delivery Tissue Hypoxia Adult Respiratory Distress Syndrome Thermodilution Cardiac Output
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