Figure 3.

Mean pulmonary arterial pressure and mean arterial blood pressure versus cardiac output during mechanical ventilation (circles) and at the start (triangles) and end (squares) of spontaneous breathing trials on Control day (closed symbols) and Study day (open symbols). Substantial increases in mean pulmonary arterial pressure and mean arterial blood pressure on Control day were cancelled by nitroglycerin infusion on Study day and a similar increase in cardiac output occurred on both days, strongly suggesting that nitroglycerin infusion on Study day abandoned the increased right and left ventricular afterload on Control day.