The Occlusion test of pulmonary artery of operation side was carried out whenever the functional impairment of the opposite lung was assumed to be dangerous. On the other hand, the cardiopulmonary function of the cases which developed complications was investigated to study the functional limit. Thus the following results were obtained. Values when a steady state was reached after pulmonary artery occlusion on the operative side were found in general to be stable in A and B groups, while in most cases of C, D and F groups cardiopulmonary function was markedly lowered. The modes of variation in pulmonary arterial meen pressure by the Occlusion test falls approximately into 4 types, the difference between type I and II being minimal and type III indicating distinct impairment as compared with type I and II. Minute care is required in selecting the method of operation in type III cases. Type IV consists of those with compensatory failure; total lung-resection of the side is contraindicated and other surgical procedures should be tried with extreme caution. A considerable correlation was noted in the % vital capacity of the opposite lung befor Occlusion and the type of pressure variation, and type III had the poorest result. Complications during and after operation were most often encountered in cases with % V. C. and % M. B. C. each below 60, % V. C. of the opposite side below 30%, pulmonary arterial mean pressure above 20 mmHg and SaO(2) below 60% by 10% low oxygen load.
Their incidence was the highest in thoracoplsty, which could be prevented by a series of fractional operations. Pneumonectomy had the lowest incidence of complication. No complication occurred in caces the method of urgery was selected by analysis of pressures variation types after the pulmonary artery Occlusion.