Pulmonary function after biventricular bypass for autologous lung oxygenation

Biventricular bypass (BVB) with autologous lung perfusion is an attractive concept to ameliorate systemic inflammatory response by eliminating the oxygenator from the extracorporeal circulation. The effect of biventricular bypass as compared to heart-lung bypass (HLB) on pulmonary function parameters was therefore studied in an experimental model.

Heart-lung bypass using a membrane oxygenator or biventricular bypass using the autologous lung for gas exchange was performed for 120 min in an alternating series of 12 mongrel dogs with the heart arrested for 90 min by crystalloid cardioplegia and 30 min reperfusion, followed by a 120 min observation period. Systemic (CO, SVR) and pulmonary hemodynamics (PVR), extravascular lung water (EVLW, double indicator), gas exchange (FiO(2), PaO(2), PaCO(2)), lung compliance (PC), and ventilation (RMV) at FiO(2)=0.5 required to maintain PaCO(2) at 40 mmHg, were measured. Blood cell counts (Leuco, Thrombo) were performed.

All animals were weaned from extracorporeal circulation without inotropes, no differences were observed in cardiac output and blood pressures. The following data were obtained in % change from pre-bypass values 60 min after extracorporeal circulation (*:P<0.05, HLB vs. BVB): PVR, +108 vs. +45*; EVLW, +21 vs. -2*; PC, -12 vs. +4*; PaO(2), -8 vs. +21; RMV, +21 vs. +2*; Leuco, -65 vs. -12*; Thrombo, -62 vs. -35*.

During and after heart-lung bypass the lung is subject to severe ischemia-reperfusion injury as indicated by edema, cell trapping, and impaired gas exchange. The data demonstrate superior preservation of pulmonary mechanics and function after biventricular bypass as compared to heart-lung bypass and support the clinical strategy of using biventricular bypass in patients with impaired lung function.