The Use, Abuse, and Mystique of Positive End-Expiratory Pressure

Abstract

Two decades ago, positive end-expiratory pressure (PEEP) was introduced into routine medical practice amid considerable fanfare because it improved arterial oxygenation in patients with the adult respiratory distress syndrome (ARDS) (1-3). As early as 1938, however, a similar end-expiratory pressure technique using a low pressure source had already been reported for acute pulmonary edema (4), and the effect of PEEP in reducing the alveolar-arterial oxygen difference in postoperative patients also had been described (5). Soon thereafter, the effectiveness of PEEP in improving arterial oxygenation across the lung in both adults and children caught the imagination of pulmonologists, respiratory therapists, surgeons, pediatricians, and, indeed, anyone interested in acute respiratory failure (5-8). Thus, PEEP has become a widely used ventilatory technique. At the same time, it is often used indiscriminately, without consideration of possible adverse consequences. Although PEEP application usually improves arterial oxygenation at a given inspired oxygen fraction (FI02), it also can decrease cardiac output and, therefore, result in a net decrease in tissue oxygen delivery (6). Other adverse effects of PEEP include the possibility of inducing an increase in extravascular lung water at higher levels (e.g., 15 cm H20) of PEEP (7), elevated intracranial pressures (8), barotrauma (9), and the rare situation where PEEP actually impairs oxygenation (10). This perspective is based on my personal experiences with PEEP and on the contributions of many others who have advanced our knowledge about the applications of PEEP in critically ill patients requiring mechanical ventilation for refractory hypoxemia.