title: The alveolar-arterial oxygen gradient in patients with documented pulmonary embolism.
abstract: It has been reported that the finding of a normal PaO2 level on arterial blood gas analysis does not exclude the diagnosis of acute pulmonary embolism. We wished to determine whether a more thorough evaluation of the blood gases would prove more helpful; specifically, whether it is possible for a patient with acute pulmonary embolism to have a normal alveolar-arterial (A-a) oxygen gradient. We studied this question in a patient population in which the diagnosis was definitively made via pulmonary arteriography. Sixty-four patients met all study criteria. In these patients, the A-a gradient ranged from 11.6 to 83.9 mm Hg (mean, 41.8 mm Hg). In three patients, the A-a gradient was normal for age. We conclude that a normal A-a oxygen gradient does not exclude the diagnosis of acute pulmonary embolism, and should not preclude further diagnostic procedures if there is a high index of suspicion.
mesh_terms: D000208:Acute Disease; D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002245:Carbon Dioxide / Q000032:analysis; D005260:Female; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008297:Male; D008875:Middle Aged; D010100:Oxygen / Q000032:analysis* / Q000097:blood; D010313:Partial Pressure; D011650:Pulmonary Alveoli / Q000032:analysis*; D011651:Pulmonary Artery / Q000000981:diagnostic imaging; D011655:Pulmonary Embolism / Q000175:diagnosis* / Q000000981:diagnostic imaging; D011859:Radiography; D012189:Retrospective Studies
chemical_list: D002245:Carbon Dioxide; D010100:Oxygen