Studies on Changes in the Pulmonary Circulation before and after Operation of the Aged Patients

　1）　In the aged, there were disturbances　of the pulmonary circulation even before　operation.　These disturbances were mostly　seen in perfusion and diffusion, and it was　known that the impairment of diffusion was　due to increase of the distribution component.

　2）　During the open thorax, the pulmonary　circulation was extremely changed, and venti—lation, perfusion and diffusion were disturbed　in all points.　However, there was no dif—ference of the disturbances between the aged　and the younger.

　3）　The recovery of ventilation after oper—ation was well in the aged as in the younger.　However, the impairments of perfusion and　diffusion remained persistently in the post—operative course of the aged.　Particularly，　diffusion was impaired in a type of increase　of the distribution component.

　4）　The grade of lowering of the oxygen　saturation of the peripheral arterial blood　caused by the low oxygen inhalation was a　good indication in order to assume the post—operative changes of the pulmonary circu—lation of the aged before operation.