Document Detail

Swallowing of lung liquid and amniotic fluid by the ovine fetus under normoxic and hypoxic conditions.
MedLine Citation:
PMID:  8092226     Owner:  NLM     Status:  MEDLINE    
OBJECTIVE: The lungs of the mammalian fetus secrete large volumes of fluid daily. The purpose of this study was to estimate the fraction of the lung liquid that is swallowed as it exits the fetal trachea versus that which enters the amniotic fluid under normoxic and hypoxic conditions. STUDY DESIGN: In chronically catheterized fetal sheep at 119 to 133 days' gestation the volume of fluid swallowed by the fetus was monitored five times per day for three consecutive 24-hour periods: control, hypoxia, and recovery. The Na+, K+, and Cl- concentrations of the swallowed fluid, lung liquid, and amniotic fluid were measured simultaneously. The fraction of the swallowed fluid that originated from the lungs or amniotic fluid was calculated from 24-hour average compositions and the assumption that the fetus swallowed only amniotic fluid and lung liquid. RESULTS: During the control, hypoxia, and recovery periods the fetuses swallowed 264 +/- 43 (SE), 92 +/- 23, and 271 +/- 24 ml/kg of fetal weight per day, respectively. As determined from Cl- concentrations, this swallowed fluid was composed of 17.7% +/- 2.7%, 24.8% +/- 5.8%, and 11.9% +/- 3.4% lung liquid, respectively, with the remainder being amniotic fluid. Throughout the three 24-hour observation periods there was an inverse relationship between the net 24-hour swallowed volume and the fraction of the swallowed fluid that originated from the lungs. Calculations based on Na+ concentrations yielded essentially the same results with slightly more scatter, whereas calculations based on K+ concentrations were unreliable. CONCLUSIONS: (1) Chloride concentrations provide the best of the three index values for a compositional analysis of fluids swallowed by the fetus. (2) Under normoxic conditions around 18% of swallowed fluid is derived from the fetal lungs. (3) On the basis of published fluid secretion rates for the fetal lung, an average of 50% of the liquid that exits the fetal trachea is swallowed and the rest mixes with the amniotic fluid.
R A Brace; M E Wlodek; M L Cock; R Harding
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  American journal of obstetrics and gynecology     Volume:  171     ISSN:  0002-9378     ISO Abbreviation:  Am. J. Obstet. Gynecol.     Publication Date:  1994 Sep 
Date Detail:
Created Date:  1994-10-18     Completed Date:  1994-10-18     Revised Date:  2007-11-14    
Medline Journal Info:
Nlm Unique ID:  0370476     Medline TA:  Am J Obstet Gynecol     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  764-70     Citation Subset:  AIM; IM    
Department of Physiology, Monash University, Clayton, Victoria, Australia.
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MeSH Terms
Amniotic Fluid / metabolism*
Chlorides / metabolism
Extravascular Lung Water / metabolism*,  secretion
Fetal Hypoxia / metabolism*,  physiopathology
Lung / embryology*,  secretion
Potassium / metabolism
Sodium / metabolism
Grant Support
Reg. No./Substance:
0/Chlorides; 7440-09-7/Potassium; 7440-23-5/Sodium

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