Positive End Expiratory Pressure, or PEEP, is getting a lot of attention lately. First described in 1938 as an addition to mechanical ventilation that improved oxygenation1 in acute pulmonary edema, asphyxia and sepsis, the hemodynamic effects of PEEP prevented its widespread use until the 1960s. By 1970, PEEP had gained traction in treating premature neonates with respiratory distress2 and adults with acute respiratory distress syndrome (ARDS).3 Today, a growing body of literature suggests that PEEP benefits a wide variety of patients with respiratory distress and might well be useful any time you need to assist ventilations.
Simply defined, PEEP is the pressure above atmospheric pressure measured in the alveoli at end expiration. It is one of the first ventilator parameters set and would typically be “dialed in” to between 3 and 5 cmH2O, sometimes referred to as, “physiologic PEEP.”4 This positive, end expiratory, pressure serves to prevent collapse of the alveoli at end expiration as well as to prevent repeated opening and closing of the alveoli, which is thought to cause ventilator-induced lung injuries. PEEP may also serve to recruit already collapsed alveoli, reopening them so they can participate in gas exchange.5 The primary use of PEEP has typically been to improve oxygenation. PEEP can also be applied when using a bag-valve mask by attaching a PEEP valve to the bag and selecting the level of PEEP desired (see illustration). Some bag-valve-masks are manufactured with integral PEEP valves.