An inspiratory fall in systolic arterial pressure of more than 10 mm Hg (pulsus paradoxus) was noted in 30 of 61 patients with shock. Inspiratory right atrial pressures and total blood volumes were significantly lower in patients with pulsus paradoxus. Rapid infusion of dextran in 22 patients usually was effective in reversing the exaggerated inspiratory fall in systolic pressure. Total peripheral vascular resistance tended to be higher in the patients with pulsus paradoxus and administration of vasoconsrictor drugs often accentuated the respirator pressure variation.
