Do the NIH ARDS Clinical Trials Network PEEP/F_IO2 Tables Provide the Best Evidence-Based Guide to Balancing PEEP and F_IO2 Settings in Adults?

Abstract

Positive end-expiratory pressure (PEEP) and inspired oxygen fraction (F_IO2) are the primary means of improving P_aO2 during mechanical ventilation. Patients with acute respiratory distress syndrome (ARDS) typically present with a large intrapulmonary shunt, which makes even high F_IO2 ineffective in improving P_aO2. PEEP decreases intrapulmonary shunt by recruiting collapsed alveoli, but PEEP is associated with important adverse effects, whereas prolonged exposure to high F_IO2 may cause oxidative lung injury. The improved survival found in the National Institutes of Health's ARDS Network low-tidal-volume study may suggest that their PEEP/F_IO2 titration tables represent the best method for adjusting these variables. Based upon an extensive literature review of PEEP and respiratory system mechanics in ARDS, we conclude that: (1) for most patients the therapeutic range of PEEP is relatively narrow, so the ARDS Network PEEP/F_IO2 strategy is reasonable and supported by high-level evidence, (2) how best to adjust PEEP to prevent or ameliorate ventilator-associated lung injury is unknown and still under investigation, and (3) in a small subset of patients with severe lung injury and/or abnormal chest-wall compliance, highly individualized titration of PEEP, based upon the respiratory-system pressure-volume curve, PEEP/tidal-volume titration grids, or a recruitment maneuver and a PEEP decrement trial is a reasonable alternative.