RESUMO
31 patients suspect for acute pulmonary emboli were studied by measuring arterial PO2 (room air) and right to left shunt (100% oxygen breathing) to determine if measurement of the right to left shunt aided in the diagnosis of pulmonary embolism. Ventilation/perfusion or serial perfusion lung scans were performed on each patient. All patients exhibited arterial hypoxemia (PaO2 less than or equal to 80) and 27 had a shunt greater than 7%. The shunt was 15.1 +/- 3.6% in 9 patients with lung scans highly suggestive of emboli. 20 patients with lung scans of low probability for emboli had significantly less shunting averaging 10.9 +/- 3.7%. 5 patients of the latter group had shunts averaging 15.2 +/- 3.8% attributable to occult pneumonia not initially apparent. An increased right to left shunt fraction is not diagnostic of pulmonary emboli, but a normal one makes the diagnosis unlikely.