Positive End-Expiratory Pressure in Refractory Hypoxemia

Abstract

Positive end-expiratory pressure was used in 15 patients with severe hypoxemia because we could not attain an arterial Po₂ of 50 mm Hg or greater with intermittent positive-pressure ventilation and an inspired O₂ concentration of 50% or less. Before the institution of positive end-expiratory pressure, arterial Po₂ levels ranged from 22 to 76 mm Hg, with inspired O₂ concentrations of 40% to 100%. In all but one patient positive end-expiratory pressure, using inspired O₂ concentrations of 30% to 50%, resulted in arterial Po₂ levels ranging from 60 to 219 mm Hg. Measurements of central venous pressure, arterial blood pressure, pulse rate, and urine output showed no deleterious changes from this procedure. Positive end-expiratory pressure seems to effectively achieve adequate arterial Po₂ levels without the use of potentially toxic inspired O₂ concentrations, in patients with otherwise refractory hypoxemia. It apparently prevents alveolar collapse during expiration, thus improving ventilation-perfusion relationships.