• blood gas;
  • alveolar-arterial oxygen gradient;
  • oxygen-tension indices


With respiratory therapy in critically ill veterinary patients becoming more commonplace, a consistent Indicator of pulmonary function status is necessary. Although calculation of the pulmonary shunt fraction correlates well with the degree of pulmonary dysfunction, lts detetmination requires placement of a pulmonary arterial catheter, an invasive procedure that may not be practical in many clinical situations. Using Information obtained from the atterial blood gas, many other oxygen-tension derived Indices have been suggested as noninvasive measurements of the efficiency of pulmonary gas exchange, lncluding the alveoiar-arterial oxygen tension difference, the ratio of arterial to alveolar oxygen tension, the ratio of arterial to inspired oxygen tension, and the ratio of alveolar-arterial gradient to arterial oxygen tension. A total of 427 blood gas values from 195 different patients were evaluated. A loglstic regression model using a stepwise algorithm was constructed to assess potential multicollinearity and interaction between factors. The only factors that contributed significantly to the model predictive of survival were age (p < 0.015), base excess (p < 0.029), and the alveolar-arterial oxygen tension difference (p < 0.014).