気管支喘息における局所換気と肺気量の不均等性に関する研究

Studies on unevenness of regional ventilation and volume in patients with bronchial asthma

　これ迄，気管支喘息発作時の病態は主として総肺機能的見地より検討が加えられてきた。しかし発作時に聴取される異常呼吸音の経時的変化や，あるいは吸気分布不均等指数，⊿N₂や血液ガスなどの所見の推移から気道病変の不均等性が推測きれても，これ迄のいわゆる呼吸機能検査法ではその不均等性を地理的に視覚的に，かつ定量的に表現することは不可能である。

　近年，肺機能検査に用いられる放射性同位元素の種類も増え，検査の目的に応じて適宜に選択しうるし，更にγ線の検出器およびデータの収録や画像処理に必要な周辺機器の著しい進歩に伴って，病態の経時的変化を局所的に把握しうる様になった。

　The regional minute ventilation per volume (V_E/V) and the regional FRC, the regional fast and slowspaces in patients with asthma in remission and during the attack were studied in this paper.

　For this purpose, by using a scintillation camerathe patients rebreathed 5 mCi of xenon-133 for about5 minutes in a closed circuit. After equilibrium was reached, xenon-133 was washed out from the lungs. The image of the lungs was divided in six regions, that is, left and right, upper, middle and lower. The counts of xenon-133 were plotted on semilogarithmic scale against time from each region. Then spirometry was performed.

　In eleven out of fifteen cases with more than 70% of FEV_1.0% had abnormal values of (V_E/V) in some regions. In an asymptomatic case of a twentyfive year-old female, FEV_1.0% was 80%. However, the value of (V_E/V) decreased in the right lung field. The static image showed the delay in washout of xenon-133 in the right lung which was compatible with the data of (V_E/V).

　During the attack, there were decrease in forced expiratory volume in one second, and increases in FRC, index of inspired gas distribution and ΔN2. Comparing values of (V_E/V) in the acute attack with those in remission, the ratios in all six pulmonary regions increased in one case and the ratios in all regions decreased in two case. In three cases, one out of six pulmonary regions increased and other decreased.

　During the attack, regional slow spaces increased generally. Comparing values of regional (slow space/ FRC)% during the attack with those in remission, ratios increased markedly especially in middle and lower lung field in five out of six patients.

　From the above data it was concluded that unevenness in regional V_E/V and regional FRC was one of the pathophysiological features in asthma.