PEEP titration: new horizons.

Most respiratory practitioners agree that PEEP helps to recruit and maintain alveoli that would otherwise collapse or suffer tidal inflation and deflation. PEEP thus reduces atelectrauma, shear forces, and systemic inflammatory mediator release. These benefits are balanced against consequences. PEEP can lead to overdistention of lung units, especially those that remain normal in the midst of heterogeneous lung injury. High PEEP does not always translate to an “open lung”; several studies have shown that atelectasis actually increases when PEEP is set above the optimal level, due to ventilator-induced lung injury or collapse in dependent areas in the setting of overdistention of others.1-3 Animal studies have described the cellular level pathophysiology for PEEP above and below levels that achieve optimal oxygenation and elastance. Low4-6 and high PEEP5,6 ventilation in mice increased histological lung injury, including edema, hemorrhage, and inflammation. PEEP can have adverse hemodynamic effects related to reduced right-ventricle filling and increased afterload on the right ventricle.7