MATCHED VENTILATION-PERFUSION BECOMES MISMATCHED VENTILATION-PERFUSION LUNG IMAGING AFTER RESOLUTION OF CARCINOMA OF THE BRONCHUS

Airway occlusion results in regional alveolar hypoxia followed by reflex hypoxic pulmonary arterial constriction. Ventilation-perfusion imaging demonstrates matched defects. In the two patients reported, occlusion of the main bronchus by bronchogenic carcinoma was resolved-in one case by radiation therapy, and in the other by removal of the tumor mass in the bronchus by bronchial slitted biopsy. The initially matched ventilation-perfusion findings became mismatched. While ventilation was presumed to be normal, pulmonary perfusion was not completely reversed.