Quantification of the determinants of arterial hypoxemia in critically ill patients.

A quantification of the determinants of arterial hypoxemia was performed in 376 cardiorespiratory measurements obtained from 180 critically ill patients. Statistical analysis showed that pulmonary venous admixture (Qsp/Qt) could explain only 48% of the PaO2 variability in the sample of measurements taken (r2 = 0.48), while the effect of central venous O2 tension (PVO2) brought the total explained PaO2 variability up to 82% (total r2 = 0.82). These findings imply that pulmonary function is not the only determinant of PaO2; the PVO2-mediated effect of other cardiovascular and metabolic determinants must be recognized in the clinical setting.