Mechanical ventilation and fluid management in acute lung injury. Effects on gas exchange and hemodynamics

Basic therapy of acute lung injury (ALI) covers a pressure-limited lung protective mechanical ventilation with low tidal volumes (68 ml/kg ideal body weight), adequate positive end-expiratory pressure (PEEP) combined with early recruitment maneuvers and a restrictive fluid management (in hypoproteinemic patients preferably with albumin and diuretics). These measures aim at providing sufficient oxygenation while simultaneously minimizing airway pressure, atelectasis and edema formation. The main hemodynamic effects are a decrease in cardiac output and in systemic arterial pressure potentially reducing organ perfusion. However, successful therapy reduces hypoxic pulmonary vasoconstriction and hypercapnia, thus lowering pulmonary artery pressure, unloading the right ventricle, and stabilising hemodynamics.