Effect of high frequency oscillatory ventilation on fluid filtration rate in isolated perfused rabbit lungs

We have studied the effect of changing ventilatory frequency (VF) of high frequency oscillatory ventilation (HFOV) on fluid filtration rate (FFR) in twelve isolated rabbit lungs perfused at constant blood flow. Mean pulmonary artery pressure (Ppa), mean left atrial pressure (Pla), airway pressure (Paw), pulmonary vascular resistance (PVR), pH, O2 and CO2 partial arterial pressures (PaO2 and PaCO2) and plasma colloid osmotic pressure (COP), were measured. We ventilated the lungs with a modified Bird Mark 7 ventilator which could achieve HFOV (range 5-30 Hertz). In each experiment VF was randomly varied on ten different occasions, maintaining each variation for ten minutes. The first group of six rabbits was ventilated under normal haemodynamic conditions. The other six rabbits were ventilated after the production of hydrostatic lung oedema. Blood gas exchange in both groups of rabbits was satisfactory. There was no statistically significant correlation between VF and FFR. We conclude that variations in VF using HFOV does not alter lung fluid balance in normal and in hydrostatic oedema rabbit lungs.