ADDITIVE NATURE OF DISTENSION AND SURFACTANT PERTURBATION ON ALVEOLOCAPILLARY PERMEABILITY

The aim of this study was to determine whether the Effects of alveolar distention and surfactant dysfunction on alveolocapillary barrier fun ction are different and additive. Pulmonary clearance of aerosolized t echnetium-99m-labelled human serum albumin ((99)mTc-HSA) was used to c haracterize barrier function after perturbing the surfactant system wi th the detergent dioctyl sodium sulphosuccinate either singly or in co mbination with large tidal volume ventilation (LTVV). Clearance was me asured for 3 h (Experimental ventilation) in four groups (n=6 each) of rabbits: 1) Controls; 2) Detergent; 3) LTVV; and 4) Detergent+LTVV. R estoration of clearance (Recovery) was studied for 3 h under conventio nal ventilation. The half-life of clearance (t1/2) decreased during LT VV (305 min) compared to 1,055 min in Controls. Detergent induced a bi exponential clearance with slow (t1/2S) and fast (t1/2F) half-lives of 670 and 15.4 min, respectively. The fast fraction (fF) was 0.20. Clea rance in the Detergent+LTVV group was also biexponential. The t1/2F an d fF were similar to the Detergent group. The t1/2S was similar to the LTVV group. The fF in this group increased to 0.36 during Recovery (p <0.01 versus Detergent group and p<0.05 versus Experimental ventilatio n).The diverse kinetics of clearance during large tidal volume ventila tion and surfactant dysfunction suggest the presence of different mech anisms affecting the barrier. The mechanisms have additive characteris tics, which superimpose to produce lung injury.