1330 TESTING AN ARTIFICIAL SURFACTANT (AS) IN PREMATURE LAMBS

Abstract

We treated six 120-day gestational age lambs with 100 mg/kg of AS, a 9:1 mixture of 14C-labeled saturated phosphatidylcholine (SPC) and phosphatidylglycerol, minimal surface tension (ST) 3.6 ±1.3 dynes/cm. In the 1st hr of life, pH and pCO2 in AS lambs were similar to those of untreated lambs (UL), while pO2=60±9 for AS lambs vs pO2=25±2 for UL (p<.01). All lambs were treated with 3H-labeled sheep natural surfactant (NS), ST=O. At treatment all lambs had: pH=6.92±0.03; pCO2=109±6 mmHg. The lambs responded similarly to NS; pH, >7.25 and pCO2, <55 mmHg. However, pO2 remained >100 mmHg for 2.5±5 hr in lambs previously treated with AS vs 0.9±.3 hr in the other lambs (p<.01). The changes in the 3H and 14C specific activities (CPM/μmole SPC) recovered by alveolar wash at sacrifice suggest that more than 50% of the AS was no longer associated with the airways. Airway samples taken from AS lambs before treatment with NS had ST=32±2.9, while reisolated material from these samples by centrifugation had ST=0. Using an ST increase to >10, AS is 10 times more sensitive to inhibition by fetal lung fluid than NS (p<.01). AS restored the pressure volume curves (PV) of surfactant depleted adult rat lungs, but AS did not improve the PV of premature lamb lung while NS caused large PV changes (p<.01). In summary: 1) AS affects the pO2 response of lambs. 2) AS seems to be rapidly cleared from the airways. 3) AS is more sensitive than NS to inhibitors of ST. 4) Premature lungs respond differently to AS than adult lungs.