Reducing lung liquid volume in fetal lambs decreases ventricular constraint

Background This study evaluated whether an increased left ventricular (LV) pump function accompanying reduction of lung liquid volume in fetal lambs was related to increased LV preload, augmented LV contractility, or both. Methods Eleven anesthetized preterm fetal lambs (gestation 128 ± 2 days) were instrumented with (1) an LV micromanometer-conductance catheter to obtain LV end-diastolic volume (EDV) and end-diastolic pressure (EDP), the maximal rate of rise of LV pressure (d P /d t max ), LV output, LV stroke work, and LV end-systolic elastance ( E es ), a relatively load-independent measure of contractility; (2) an endotracheal tube to measure mean tracheal pressure and to reduce lung liquid volume. LV transmural pressure was calculated as LV EDP minus tracheal pressure. Results Reducing lung liquid volume by 16 ± 4 ml kg −1 (1) augmented LV output (by 16%, P = 0.001) and stroke work (29%, P