側面よりみた局所換気機能の検討

Studies on regional ventilation observed from a lateral side of the chest

　1955年Knippingら1）は肺局所換気を測定するために放射性同位元素xenonを用いた。以来この分野における諸家の報告は，腹背または背腹方向からみた重力による上下の不均等換気に関するものが多い^2,3）。しかし近年，重力の因子以外に呼吸筋の動きによって生ずる不均等換気が指摘されている^4〜6）。この呼吸運動，ことに横隔膜運動の換気に及ぼす影響は，xenonによる側面からの局所換気の測定によって推測可能と考え，以下の如き検討を試みた。

Three normal subjects ranging in age from 27 to 35 and three patients with unilateral pulmonaryresection were studied. The subjects were seated. A scinticamera was placed for dorsal or lateral side of the chest. The subject was instructed to inhale 5 mCi of xenon-133 from functional residual capacity. During rebreathing in the spirometer circuit, car-bon dioxide was removed by a soda-lime absorber and oxygen was added at a rate sufficient to main-tain a constant volume. External counts were measured for determinating a half-time (T_1/2) of washout during normal breathing at rest after equilibrium was reached. The influence of xenon-133 entered in the chest on external counts was corrected. It was found that about 10% of radioactive counts of xenon-133 in the right lung were detected from lateral view of the left side of the chest in the patients. The value of a half-time in the dorsal lower portion of the lung was the smallest, that is, the portion was somewhat better ventilated than the others. Horizontal uneveness as well as vertical uneveness of ventilation were observed. Horizontal uneveness was influenced by the move-ment of diaphragma and by a belly-band.