<原著>第 1 編 Closing volume の実験的研究特に肺循環異常が窒素洗出し曲線と圧量曲線とにおよぼす影響について(Closing volume に関する実験的ならびに臨床的研究)

Abstract

Experiments were performed to elucidate the effect of gravity on the P-V curves, single breath nitrogen washout curves and closing volume in the lung with circulatory disturbances. Single breath nitrogen washout curves were studied in 20 anesthetized dogs using a newly devised method in which active expiration was conducted by elevating diaphragm through the changes of intraperitoneal pressure. Expiratory nitrogen concentrations were compared between alive and dead on each single animal for the purpose of detecting the effect of gas exchange on nitrogen curve. The interrelationship between nitrogen curves, closing volume (CV) and transpulmonary pressure (Ptp) volume curves in circulatory abnormalities were also studied in various stages of alloxan induced pulmonary edema. The results were as follows. 1) The assessed reproducibilities of CV, Ptp and inflection point volume (IPv) (volume from inflection point to RV point) were good and each value did not change much within the time course of experiments. 2) While the nitrogen concentration measured over the phase III and IV of the dead animals were lower than that of the alive, the measured closing volume were identical in both states. 3) Inflection point (IP) was likely dependent on the level of balloon position in esophagus, since the higher the level of balloon position was, the higher the lung volume at which IP occurred. The IP likely indicates the onset of closure at the level of lung where the balloon was situated. 4) CV started to increase 0-10 min. after alloxan administration. In the stage where CV was increasing, starting point of phase IV always occurred at higher lung volume compared with IP. On the contrary, as CV was decreased in the time course of edema formation, IP was found to occur at higher lung volume than CV as in control stage. No discrepancy between IP and CV was found in intact lung. 5) A close relation between change of CV and pulmonary compliance was demonstrated during the entire course of