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July 1988

The Alveolar-Arterial Oxygen Gradient in Patients With Documented Pulmonary Embolism

Author Affiliations

From the Department of Emergency Medicine, William Beaumont Hospital, Royal Oak, Mich.

Arch Intern Med. 1988;148(7):1617-1619. doi:10.1001/archinte.1988.00380070107025

• 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 arterlography. 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.

(Arch Intern Med 1988;148:1617-1619)