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

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.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.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.Recent studies have shown that lung protective strategies using low tidal volumes and high levels of positive end-expiratory pressure (PEEP) reduce mortality and are becoming standard practice in patients with acute respiratory distress syndrome (ARDS) [1,2].Although PEEP improves arterial oxygenation, it can adversely affect systemic hemodynamics, reducing venous return and cardiac output. These effects are proportional to the PEEP level. Regional perfusion can also be affected by PEEP, independently of cardiac output changes. The splanchnic perfusion is particularly sensitive, and any reduction can compromise its barrier function, promote bacterial translocation, and contribute to the development of multiple organ failure [3]. In experimental models, PEEP has markedly decreased mesenteric and portal blood flow, despite only moderate reductions in cardiac output [4-8]. Similar results have been repo