Effects of PEEP levels following repeated recruitment maneuvers on ventilator-induced lung injury

Background: Different levels of positive end-expiratory pressure (PEEP) with and without a recruitment maneuver (RM) may have a significant impact on ventilator-induced lung injury but this issue has not been well addressed. Methods: Anesthetized rats received hydrochloric acid (HCl, pH 1.5) aspiration, followed by mechanical ventilation with a tidal volume of 6 ml/kg. The animals were randomized into four groups of 10 each: (1) high PEEP at 6 cm H2O with an RM by applying peak airway pressure at 30 cm H2O for 10 s every 15 min; (2) low PEEP at 2 cm H2O with RM; (3) high PEEP alone; and (4) low PEEP alone. Results: The mean arterial pressure and the amounts of fluid infused were similar in the four groups. Application of the higher PEEP improved oxygenation compared with the lower PEEP groups (P < 0.05). The lung compliance was better reserved, and the systemic cytokine responses and lung wet to dry ratio were lower in the high PEEP than in the low PEEP group for a given RM (P < 0.05). Conclusions: The use of a combination of periodic RM and the higher PEEP had an additive effect in improving oxygenation and pulmonary mechanics and attenuation of inflammation.