DOSE DEPENDANT EFFECTS OF SURFACTANT ON LUNG MECHANICS

Abstract

Although exogenous surfactant replacement was proven to improve lung mechanics in clinical HMD (Fujiwara et.al. TA), optimal concentration and dose were not known. We studied the effect of different concentrations and quantity of TA in premature rabbits before first breath. Group A was treated with fixed lipid quantity, but variable TA concentration. Group B was treated with fixed concentration, but variable lipid quantity. We measured P-V curve (P-V) and lung-thorax compliance (CL) at 5 mg/ml to 40 mg/ml of concentration and 25 μg to 400 μg of quantity. Group A P-V curve data is given below. (Mean ± S.E.). In Group A, when lipid quantity was kept constant the variable concentration 10 mg/ml to 40 mg/ml of TA did not change the P-V curve and the CL. However when concentration of TA dropped to 5 mg/ml, the P-V curve and the CL changed adversely (p<0.02). Group B P-V curve and CL improved to maximum at 800 μg irrespective of concentrations. Further, the lipid quantity of 800 μg to 4000 μg had no further beneficial or adverse effect. We conclude 10 to 40 mg/ml of TA concentration,and lipid quanity of 800 μg to 4000 μg will have optimal effect on P-V curve and CL when instilled before the first breath.(*P5=5 cmH20 distending pr.).