Study of hemodynamic changes with oxygen inhalation in VSD associated with pulmonary hypertension.

Pre- and postoperative pulmonary hemodynamic changes were studied in 28 cases with ventricular septal defect, in whom pulmonary-systemic blood pressure ratio was more than 70%. Pp/Ps decreased and Qp/Qs increased in majority of cases and Rp/Rs decreased in all cases after 100% oxygen inhalation. In survivors, Rp/Rs decreased to under 0.5 and Qp/Qs increased to more than 2.0 after oxygen inhalation or radical operation. In nonsurvivors, Rp/Rs decreased but stayed over 0.5, and Qp/Qs increased but stayed under 2.0. It is emphasized that when Rp/Rs falls down to under 0.5 after oxygen inhalation, it will be an enough indication for operation even pulmonary hypertension is so advanced in the ventricular septal defect.