ABSTRACT
In patients with suspected pulmonary embolism, the other tests usually ordered are an electrocardiogram (ECG) and arterial blood gases. These are of more use for manage ment than diagnosis. Only rarely will the ECG show signs of acute right heart strain, but other cardiac conditions, such as arrhythmias or evidence of ischemia or infarction, may be identified. The usual arterial blood-gas findings in pulmonary embolism-of mild to moderate hypoxemia and respiratory alkalosis-are seen in many other pulmonary condi tions. An arterial P02 in the normal range is seen in about 15% of patients with acute pulmonary embolism, as it takes embolization of two lung segments before the Pq2 falls below the normal range. A normal alveolar-arterial oxygen tension difference, once thought to exclude the diagnosis, is also seen in 10-15% of patients with acute pulmonary embolism.
