Pulmonary protection and respiratory support

Acute lung injury is the second common complication of cardiopulmonary bypass (CPB) after the heart, which varies from mild pulmonary dysfunction to fatal acute lung injury. CPB is the preferred method to repair several intracardiac and major vascular pathologies with adequate body perfusion and oxygenation. Owing to its nature, the heart and both lungs should be bypassed partially during CPB and totally under aortic cross-clamping to provide bloodless and motionless surgical field. During open-heart surgery under CPB, various factors such as extracorporeal circulation, hypothermia, surgical procedure, anesthesia, medications, and blood product transfusions can cause a diffuse lung damage. But, two risk factors, that is, ischemia and foreign surfaces, are the main determinants of the development of perioperative respiratory failure. During CPB, the lungs only receive blood from the diminished bronchial arterial flow, leading to pulmonary ischemia. Particularly, nonpulsatile CPB flow causes several changes in the lungs, leading to impaired lung parameters, such as decreased tissue energy source, changes in newly developed structures, and increased severity of inflammation. Several preventive approaches have employed to decrease lung injury, to improve gas exchange, and to prevent exacerbation of inflammation, such as shortened surgery, using leukocyte depletion filters, ultrafiltration, miniaturized circuits, and using biocompatible surfaces.