[Regional pulmonary function in intra-emphysematous bulla and peri-emphysematous bulla]

We have measured regional alveolar volume and regional ventilation of emphysematous lesions and periemphysematous lesions with positron emission tomography and N-13 gas in 10 patients. The purpose of the study was to investigate how emphysematous lesion develops. The subjects were all male (except one) who put on a mask in supine position, and were connected with a spirometer. We gave N-13 gas in this closed circuit and had the gas rebreathed by the subjects. After activity reached equilibrium in closed circuit, an equilibrium scan was made. We took "activity gas" from the closed circuit and measured activity by well counter during equilibrium to get quantitative alveolar volume. The activity in closed circuit during equilibrium showed activity in the thoracic unit. After equilibrium, we used air to wash out radioactive gas from the circuit. During washout we took 3 sequential images. The decreased rate of activity in the region of interest from these 3 sequential washout images was expressed in a monoexponential curve. The index of monoexponential denotes V/V. Alveolar volume in emphysematous lesions was 34.8 +/- 19.5 ml/100ml thoracic volume, and V/V in these lesions was 0.27 +/- 0.21/min. On the other hand alveolar volume in periemphysematous lesions was 76.5 +/- 13.1 ml/100ml thoracic volume, and V/V was 0.38 +/- 0.22/min. Thus alveolar volume in periemphysematous lesions was relatively high. These results indicate that the effect of emphysematous lesions as compared with periemphysematous lesions was not direct compression of alveolar space. The direct effect was compression to the bronchiole of peripheral lesions, and check valve mechanism occurred in the bronchiole causing peripheral lesions resulting in the destruction of the alveolar wall.