Washout of ¹³³Xenon Gas from the Lungs: Comparison with Nitrogen Washout

¹ Pulmonary Division, Department of Medicine and the Nuclear Medicine Division, Department of Radiology, University of California, San Diego, School of Medicine, La Jolla

The regional distribution of pulmonary ventilation is nonuniform in health and disease. Single and multiple breath techniques have been developed to assess this nonuniformity. Limitations of these expired gas techniques include: identification of only several of the component washout exponentials and preferential representation in this single curve of the better ventilated spaces. In ten normal persons and eight patients we assessed the washout of ventilation by three simultaneous techniques and obtained three clearance curves: nitrogen washout with 100 percent O₂; washout of ¹³³Xe at the mouth with 100 percent O₂; clearance of ¹³³Xe from the patients' lung fields. A scintillation camera/computer system was utilized to provide clearance curves for ¹³³Xe from selected zones of interest varying from both lungs to sublobar regions. In normal persons all three curves were superimposable. In patients with diffuse lung disease the expired curve for N₂ and ¹³³Xe at the mouth were abnormal but superimposable, while the xenon clearance over the lung fields revealed slower and more abnormal clearances. These latter curves provided an appreciation of the presence, localization, and extent of both slow and fast spaces.