Oxygen transport and utilization in ARDS.

The process of tissue O2 transport and utilization is complex and incompletely understood. It depends on the successful interaction of the respiratory and cardiovascular system in order to deliver O2 in sufficient amounts and at a high enough capillary partial pressure to allow for adequate diffusion into the cell. Normally, adequate amounts of O2 are available and the system can easily augment transport to meet increased metabolic demands. Under these circumstances O2 utilization is the independent variable. In adult respiratory distress syndrome (ARDS) it appears that O2 transport is not sufficient to provide for the aerobic production of all the required energy and O2 utilization becomes limited by O2 transport. The mechanism of this supply dependency is unknown, but has been shown to be associated with a poor clinical outcome.