Effect of ventilatory frequency on fluid filtration rate in isolated perfused rabbit lungs / Efecto de las variaciones en la frecuencia respiratoria sobre la tasa de filtración de líquido en una preparación de pulmón aislado de conejo

ABSTRACT

We studied the effect of varying ventilatory frequency (VF) using intermittent positive pressure ventilation (IPPV) on fluid filtration rate (FFR) in 16 isolated rabbit lung preparations perfused at constant blood flow and airway pressure (AWP). Mean pulmonary artery pressure (MPAP), AWP, pulmonary vascular resistance (PVR), pH, PaO2, PaCO2 and colloid osmotic pressure (COP) were measured. Ventilation was performed by a piston pump ventilator. VF was ahanged every 10 min. by the following schedule 25-40-55-70-40-25 breaths per min. A group of 6 rabbits was ventilated under normal hemodynamic conditions and another group of 10 rabbit was ventilated after the prodution of hydrostatic pulmonary edema. Blood gas exhange was satisfactory in both groups of rabbits. There was not statistically significant correlation between VF and FFR in the two experimental situations (p>0.05). In conclusion, VF variation using IPPV (keeping AWP constant) did not alter liquid transfer between the microvasculature and lung interstitial space under normal hemodynamic conditions nor in hydrostatic lung edema in insolated perfused rabbits lung