1804 FETAL BREATHING MOVEMENTS TRANSIENTLY INCREASE LUNG FLUID VOLUMES IN SHEEP

Abstract

Fetal breathing movements (FBM) stimulate fetal lung growth. Since lung distension has been associated with fetal lung growth, we postulated that FBM transiently increase the total volume of fluid (TVF) in the potential airways and air spaces. In 6 chronically catheterized fetal sheep (121–137 days) we cannulated the trachea with 2 small, catheters (6F balloon-tipped, 6F end-hole); the trachea remained patent. FBM (by tracheal catheter) were recorded continuously after-surgery. On alternate days after ≥9 minutes of either FBM or no FBM we inflated the balloon-tipped catheter to occlude the trachea. Then we aspirated fluid from the lungs until ≤0.4 ml/min was obtained. In 3 fetuses we measured by inulin dilution the TVF in the lungs to determine the completeness of the aspiration. The TVF after FBM were 49.0 and 51.5 ml/kg; TVF after no FBM was 43.6 ml/kg. The volume that remained after aspiration was 19.6±0.9 ml/kg (mean±SD). The daily incidence of FBM was similar on both study days for each fetus. In every fetus, the volume aspirated after FBM (69.9±18.1 ml) was greater than that after no FBM (40.8±21.4 ml)(p<0.01). When expressed as volume/body weight, the volume after FBM (26.0±3.7 ml/kg) was greater than after no FBM (20.5±2.4 ml/kg)(p>0.01). We conclude that in the fetus with a patent trachea, FBM increase the volume of fluid that can be aspirated from the lungs. This suggests that the TVF in the airways and air spaces may also increase and may stimulate lung growth. (USPHS HL-27366 and IRG UTHSCSA)

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