Regional pulmonary function assessed by C15O2 and 11CO inhalation

Regional pulmonary blood flow and diffusion were measured using positron imaging of C15O2 and 11CO. Blood flow was estimated from the monoexponential clearance rate of C15O2. The alveolar transfer rate (diffusion) was calculated by the clearance curve of 11CO and the clearance rate of C15O2 using a non-linear least-aquares fitting method. Six normal volunteers and nineteen patients with various pulmonary disorders underwent C15O2 and 11CO inhalation. In normal subjects, the alveolar transfer rates and blood flow in the lower lung field were significantly greater than those in the upper lung field. Pulmonary emboli were demonstrated as ''hot spots'' on serial positron images. In patients with interstitial fibrosis, the alveolar transfer rate was not different from that in normal subjects. However, blood flow was significantly lower than in the normals. In patients with pulmonary emphysema, the alveolar transfer rate was lower suggesting the decreased alveolar capillary beds. Thus, dynamic study using C15O2 and 11CO inhalation provides regional blood flow and diffusion, which may permit the differentiation of various pulmonary disorders. (author)