Airway Pressure Release Ventilation

Abstract

Patients with acute lung injury present with a spectrum of respiratory failure ranging from mild arterial hypoxemia with intact pulmonary mechanics to severe intrapulmonary shunting of blood and overt ventilatory insufficiency. Of the three components of respiratory therapy — continuous positive airway pressure (CPAP), oxygen supplementation, and positive pressure mechanical ventilation — only CPAP can be expected to reverse any of the pathophysiologic alterations causing the symptoms of hypoxemia and increased respiratory work [1, 2]. Mild acute lung injury can be treated successfully using relatively low levels of CPAP to correct hypoxemia and to improve derangement in ventilatory mechanics, adding oxygen supplementation as necessary. Mechanical ventilatory assistance rarely is indicated in mild cases. More severe cases of acute lung injury require higher levels of CPAP to decrease respiratory work, but once optimum CPAP is applied, the patient still may be able to breathe spontaneously without difficulty. In severe cases of acute lung injury, however, ventilatory failure often is present, even with optimum CPAP therapy, and mechanical ventilatory assistance must be initiated.