Right ventricular function in respiratory distress syndrome and subsequentpartial liquid ventilation - Homeometric autoregulation in the right ventricle of the newborn animal

Infant respiratory distress syndrome (IRDS) and subsequent partial liquid v entilation (PLV) cause increased pulmonary vascular resistance, thus raisin g afterload. In nine newborn lambs the effects of IRDS and subsequent PLV o n right (RV) and left ventricular (LV) contractility and systolic pump func tion were assessed using indices derived from RV and LV pressure-volume rel ations, obtained by micromanometric and conductance catheters during transi ent inferior vena cava occlusion. Pulmonary function deteriorated during IR DS with a significant decrease in the ratio of arterial oxygen pressure to fraction of inspired oxygen (Pa-O2/F-lO2) whereas pulmonary artery pressure (Ppa) showed a significant increase and pulmonary vascular resistance show ed a substantial though not significant increase. Cardiac output (Q), strok e volume (SV), and end-diastolic volume (EDV) did not change. RV contractil ity showed a significant increase during IRDS: the slope of the end-systoli c pressure-volume relation (RV-E,) increased whereas its volume intercept a t 5 kPa (RV-V-5) decreased. The preload-corrected time derivative of ventri cular pressure (RV-dP/dt(max)), however, did not change significantly. LV p ump function and contractility were unchanged. During PLV pulmonary functio n showed a recovery but Ppa and pulmonary vascular resistance remained high ; indices for RV contractility showed a sustained significant increase comp ared with baseline conditions whereas indices for LV pump function and cont ractility remained unchanged. These results show that the right ventricle o f the newborn heart, in the face of increased pulmonary vascular resistance , is able to maintain cardiac output through homeometric autoregulation.