Effects of extracorporeal membrane oxygenation (ECMO) on pulmonary hemodynamics, gas exchange and prognose

Hemodynamic and gas exchange studies on acute respiratory failure patients treated by extracorporeal membrane oxygenation led to the following conclusions: pulmonary circulation can be influenced to a large extent Lamy, et al. Effects of extracorporeal membrane oxygenation on pulmonary hemodynamics by changes in bypass cannulation mode and bypass flow rate. An increase in pulmonary flow is followed by an increase in mean pulmonary artery pressure, a drop in total pulmonary vascular resistance, and an increase in shunt fraction. Forced opening of previously shut down vascular area (possibly due to hypoxic vasoconstriction) is a potential explantation for these physiological changes. Increase in bypass flow rate leads to increase in total systemic flow (pulmonary and oxygenator), but does not change total CO2 production and possibly total O2 consumption. Mixed cannulation mode (venoarterial and venovenous) guarantees adequate oxygenation of all the organs. Oxygenation of the heart can be jeopardized by venoarterial bypass, although the use of an aortic root cannula may decrease this major risk. Extracorporeal membrane oxygenation reversed the disease process in some of the patients treated. The best criteria of reversibility seem to be an improvement in arterial PO2 decrease in shunt fraction across the lung, and decrease in total pulmonary vascular resistance. The most striking change of these parameters has been observed after 2 to 3 days on bypass.