It has been reported that the pulmonary artery pressure decreased in acute induced was hyperoxia. The purpose of this study is to observe the changes of pulmonary hemodynamics and respiratory functions in acute induced hyperoxia and to clarify whether the pulmonary hypertension should be released by oxygen inhalation in patients with pulmonary impairment, or not. Materials and Methods In 9 normal subjects, 30 patients with chronic pulmonary disease (emphysema 15, fibrosis 4 bronchial asthma 4 and others 7) and 11 patients with chronic cardiac disease (mitral valvular disease 8 and aortic valvular disease 3), right heart catheterization was performed, and pulmonary hemodynamics and respiratory functions were studied before and during inhalation of 40% and then 100% oxygen. Results I Changes of respiratory functions 1) Ventilation Although there was no significant change in respiration rate and minute ventilation during others. the inhalation of high oxygen either in three groups, emphysema patients showed a tendency eases showed a slight decrease within a range of of slight decrease in respiration rate and the other groups showed that of slight increase. It was interested that minute ventilation increased slightly in normal and cardiac groups during oxygen inhalation. 2) Arterial oxygen saturation In all cases arterial oxygen saturation increased during high oxygen inhalation. 3) Arterial carbon dioxide tension There was no significant change in normal and cardiac groups. However, the pulmonary group showed a slight increase of arterial carbon dioxide tension during 100% oxygen inhalation. The average increase was 3.6 mmHg in emphysema and 1.8 mmHg in the other pulmonary patients. II Changes of circulatory hemodynamics A. Pulmonary circulation 1) Cardiac index There was no significant change in normal group. While also no significant change in the pulmonary group of 40% oxygen inhalation was found, there was slight increase of the cardiac index in that of 100% oxygen inhalation, which was within a range of -1.21 to 1.25 (average + 0.23)1 /min/M2 in emphysema and -0.13 to 0.95 (average+0.27)1/min/M2 in others. On the other hand, patients with cardiac diseases showed a slight decrease within a range of -2.88 to 0.27 (average --0.85)1/min/M2 during 40% oxygen inhalation and - 1.78 to 0.38 (average -0.49)1 /min/M2 during 100% oxygen inhalation. 2) Pulmonary artery wedge pressure (WP) In normal group, pulmonary artery wedge pressure changed with 2 mmHg or less in all cases. In the pulmonary group of 40% oxygen inhalation, patients with emphysema showed a decrease of WP within a range of - 3 to 1 (average - 1.3) mmHg and others - 7 to 6 (average -0.1)mmHg. Of 100% oxygen inhalation, the former showed a decrease within a range of -5 to 0 (average -2.2) mmHg and the latter only - 5 to 5 (average -0.7)mmHg. In the cardiac diseases group WP rose 1 mmHg on an average during 40% oxygen inhalation and remained unchanged during 100% oxygen inhalation. 3) Pulmonary artery pressure (PAP) In normal group, decrease of the pulmonary artery mean pressure (PAm) was within a range of -3 to 1 (average - 1.1)mmHg during 40% oxygen inhalation and -4 to 1 (average -2.2) mmHg during 100% oxygen inhalation.
