Effects of positive end-expiratory pressure on gastric mucosal perfusion in acute respiratory distress syndrome

INTRODUCTION Positive end-expiratory pressure (PEEP) improves oxygenation and can prevent ventilator-induced lung injury in patients with acute respiratory distress syndrome (ARDS). Nevertheless, PEEP can also induce detrimental effects by its influence on the cardiovascular system. The purpose of this study was to assess the effects of PEEP on gastric mucosal perfusion while applying a protective ventilatory strategy in patients with ARDS. METHODS Eight patients were included. A pressure-volume curve was traced and ideal PEEP, defined as lower inflection point + 2 cmH2O, was determined. Gastric tonometry was measured continuously (Tonocap). After baseline measurements, 10, 15 and 20 cmH2O PEEP and ideal PEEP were applied for 30 min each. By the end of each period, hemodynamic, CO2 gap (gastric minus arterial partial pressures), and ventilatory measurements were performed. RESULTS PEEP had no effect on CO2 gap (median [range], baseline: 19 [2-30] mmHg; PEEP 10: 19 [0-40] mmHg; PEEP 15: 18 [0-39] mmHg; PEEP 20: 17 [4-39] mmHg; ideal PEEP: 19 [9-39] mmHg; P = 0.18). Cardiac index also remained unchanged (baseline: 4.6 [2.5-6.3] l min(-1) m(-2); PEEP 10: 4.5 [2.5-6.9] l min(-1) m(-2); PEEP 15: 4.3 [2-6.8] l min(-1) m(-2); PEEP 20: 4.7 [2.4-6.2] l min(-1) m(-2); ideal PEEP: 5.1 [2.1-6.3] l min(-1) m(-2); P = 0.08). One patient did not complete the protocol because of hypotension. CONCLUSION PEEP of 10-20 cmH2O does not affect gastric mucosal perfusion and is hemodynamically well tolerated in most patients with ARDS, including those receiving adrenergic drugs.