Despite the improvement in perioperative management, the postoperative respiratory dysfunction following CPB leads to increased mortality and morbidity in cardiac surgery. Anesthesia can result in a 20% reduction in functional residual capacity. Changes in chest wall mechanics as a result of median sternotomy can contribute to prolonged alteration of forced vital capacity and respiratory function for months postoperatively.
The inflammatory response to CPB targets and amplifies in the pulmonary epithelium and endothelium resulting in increased pulmonary vascular resistance, ventilation-perfusion mismatch with intrapulmonary shunting, EVLW, and reduced surfactant activity - resulting in altered lung compliance and function.
Strategies to abrogate the respiratory compromise include modifications of CPB circuit and ventilation strategies, restrictive transfusion, and medication administration.