The heart and lungs from an independent group of rats were isolated at the 2 week time point and suspended from a calibrated force displacement transducer (ModelFT03; Grass Instruments) and lung weight was monitored continuously as described (21 (link)). The lungs were perfused and ventilated (40 breaths/min) with end-inspiratory and end-expiratory pressures of ~ 8 and 4 cm H2O. The Kf was determined using the approach described by Bongard et al. (22 (link)). The venous pressure (PV) was set at atmospheric pressure then raised to 5 cm H2O for 10 min and 13.5 cm H2O for an additional 10 min. At the end, the lungs were removed from the perfusion system, the arterial and venous cannulas connected, and pressure drop in the cannulas (ΔPcan) was determined. The pulmonary vascular pressure, RV, was then calculated using
where Pa is the pulmonary arterial pressure measured at the end of the 10-min stabilization period with Pv set at 0 mmHg, and F is the pump flow rate (0.03 ml/min/g body wt).
where Pa is the pulmonary arterial pressure measured at the end of the 10-min stabilization period with Pv set at 0 mmHg, and F is the pump flow rate (0.03 ml/min/g body wt).
