Physiology of Extracorporeal Life Support

The primary function of the heart and lungs is the provision of blood circulation, to provide oxygen (O2) and other nutrients to the cells and to remove the products of metabolism including carbon dioxide (CO2). During open-heart surgery, cardiopulmonary bypass (CPB) may be used to isolate the heart and lungs and replace whole functions of the heart and lungs during aortic cross-clamp and provide quiet, bloodless field for the performance of surgery. The utilization of CPB involves the use of an oxygenator with a cardiotomy/venous reservoir, roller or centrifugal pumps, filters, tubing, and cardiotomy suction devices. Unlike CPB, extracorporeal life support (ECLS) is one modified CPB technology used in patients with life-threatening heart and/or lung failure, including venoarterial (VA), venovenous (VV), and venovenoarterial (VVA) extracorporeal membrane oxygenation (ECMO) and VV and arteriovenous (AV) extracorporeal carbon dioxide removal (ECCO2R) [1]. The ECMO system partially takes the functions of the heart and lungs for prolonged cardiopulmonary support, allowing the heart and lungs to rest, stopping damaging heart and lung treatment, and recovering functions of the failing organs (bridge-to-recovery) or as a bridge to long-term ventricular assist (bridge-to-VAD), heart or lung transplantation (bridge-to-transplantation), or destination therapy (bridge-to-destination) for suitable candidates with irreversible disease (Fig. 1.1) [2].