Lung protective ventilation in Cardiac Surgery

Multicenter, randomized, controlled trials and meta-analyses have demonstrated that, during abdominal surgery, protective ventilation, based on low tidal volumes, positive end-expiratory pressure, and recruitment maneuvers improves postoperative outcomes (1). Protective ventilation strategies are aimed at preventing alveolar over-distension, cyclic opening and closure of peripheral airways, trans-pulmonary pressure related lung stress, recruitment and derecruitment of lung units, and local and systemic release of inflammatory mediators. Barotrauma, volutrama, and atelectrauma are all involved in ventilator induced lung injury, and it is generally accepted that protective ventilation, delivered in patients with injured lungs (acute respiratory distress syndrome), increases patients’ survival (2, 3). It is also of note that non-injured lungs (e.g. those undergoing elective surgery) may suffer from ventilator induced lung injury independently of an underlying pulmonary or extra-pulmonary disease. General anesthesia reduces muscular tone and alters diaphragmatic position promoting reduction in lung volume, alteration in ventilation/perfusion ratio, and the onset of lung atelectasis, all of which are strong predictors of pulmonary complications. Hence, mechanical ventilation is an injurious procedure. Its effects depend on intensity, duration and underlying predisposing factors. In light of this, patients undergoing cardiac surgery are particularly sensitive to lung damage for several reasons: mechanical ventilation may be long lasting, co-morbidities are frequently present, and pro-inflammatory cofactors (cardiopulmonary bypass, transfusions, ischemia/reperfuE di to ri al Lung protective ventilation in Cardiac Surgery