OXYGEN STATUS OF ARTERIAL AND MIXED VENOUS-BLOOD

Objectives: To describe system requirements for determination of the o xygen status of the blood using the oxygen status algorithm, a compute r program, To define the oxygen extractivity, a term we propose, of th e arterial blood and the oxygen extraction tension, To describe the di fferent causes of tissue hypoxia, and the clinical interpretation of m ixed venous oxygen tension and oxygen consumption rate, Data Sources: Previous physiological and clinical studies related to oxygen status o f the blood. Data Synthesis: The oxygen status algorithm calculates th e oxygen extraction tension and generates the oxygen graph as an aid i n interpreting oxygen status of the patient. A cybernetic scheme expla ins the causes of tissue hypoxia and forms the basis for the interpret ation of changes in the mixed venous oxygen tension, A diagram with th e mixed venous oxygen tension on the abscissa and the oxygen consumpti on rate on the ordinate illustrates the oxygen flux dependent oxygen c onsumption rate, A graph shows the relationship between mixed venous o xygen tension and oxygen delivery, Conclusions: The oxygen status of a rterial blood comprises three groups of quantities related to arterial oxygen tension, hemoglobin oxygen capacity, and hemoglobin oxygen aff inity. Disturbances in one of these groups may be compensated by oppos ite changes in one or both of the other. The oxygen extraction tension indicates the degree of compensation, and mixed venous oxygen tension is the key parameter in evaluating the presence of a state of oxygen flux-dependent oxidative metabolism.