A-aO2difference

A-aO2dif·fer·ence

(dif'ĕr-ĕns) The difference or gradient between the partial pressure of oxygen in the alveolar spaces and that in arterial blood. Normally less than 10 mmHg, it is increased with large right-to-left cardiac or vascular shunts.
See: alveolar air equation
Synonym(s): alveolar-arterial oxygen tension difference.