INTERPRETATION OF ALVEOLAR-ARTERIAL OXYGEN-TENSION DIFFERENCE

  • 1 January 1977
    • journal article
    • research article
    • Vol. 144  (4) , 547-552
Abstract
Errors resulting from the use of the alveolar-arterial O2 difference determined on both room air and 100% O2 were assessed in estimating changes in total shunt fraction of 41 patients hospitalized with long bone fractures. In 113 studies, changes in alveolar-arterial O2 difference in 29 patients were in the opposite direction to changes in shunt fraction. Based upon these studies, changes of less than 45 mm in the arterial O2 tension determined with a patient breathing 100% O2 are not reliable indicators of direction of change in shunt fraction. In 126 studies, the shunt fraction determined from arterial and mixed venous O2 contents in 71 patients was greater when determined on 100% O2 than when determined on room air, a possible indication of induction of alveolar or small airway collapse. Errors in estimation of shunt fraction due to assuming a value for arteriovenous O2 content difference become larger as total shunt fraction increases; in particular, use of the alveolar-arterial O2 difference as a guide to serial changes in pulmonary dysfunction can be particularly misleading when the alveolar-arterial Hb is less than fully saturated on 100% O2. Use of mixed venous samples was found necessary in these instances to avoid large errors in estimation of total shunt fraction.

This publication has 1 reference indexed in Scilit: