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This Article Full Text Full Text (PDF) All Versions of this Article: 287/5/L992    most recent 00158.2004v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Web of Science (8) Citing Articles via Google Scholar Google Scholar Articles by Pillow, J. J. Articles by Sly, P. D. Search for Related Content PubMed PubMed Citation Articles by Pillow, J. J. Articles by Sly, P. D.

Variability in preterm lamb lung mechanics after intra-amniotic endotoxin is associated with changes in surfactant pool size and morphometry

¹Centre for Child Health Research, ⁵School of Women's and Infants' Health, The University of Western Australia, and ²King Edward and Princess Margaret Hospitals, Perth 6008, Australia; ³Cincinnati Children's Hospital Medical Center and University of Cincinnati School of Medicine, Cincinnati, Ohio 45229-3039; and ⁴Department of Medical Informatics and Engineering, University of Szeged, H-6720 Szeged, Hungary

Submitted 4 May 2004 ; accepted in final form 5 July 2004

Antenatal exposure to intra-amniotic (IA) endotoxin initiates a complex series of events, including an inflammatory cascade, increased surfactant production, and alterations to lung structure. Using the low frequency forced oscillation technique as a sensitive tool for measurement of respiratory impedance, we aimed to determine which factors contributed most to measured changes in lung mechanics. Respiratory impedance data obtained from sedated preterm lambs exposed to either IA injection with saline or 20 mg of endotoxin 1, 2, 4, and 15 days before delivery at 125 days gestation were studied, and association with indexes of standard lung morphometry, inflammatory response, and alveolar surfactant-saturated phosphatidylcholine (Sat PC) pool size was demonstrated. Reduction in tissue impedance with increasing interval between exposure and delivery was evident as early as 4 days after IA endotoxin injection, coinciding with resolution of inflammatory reaction, increased alveolar surfactant pools, and contribution of alveolar ducts to the parenchymal fraction, and a later decrease in the tissue component of the parenchymal fraction. Decreases in tissue damping (resistance) were more marked than decreases in tissue elastance. Log alveolar Sat PC accounted for most variability in tissue damping (88.9%) and tissue elastance (73.4%), whereas tissue fraction contributed 2 and 6.4%, respectively. The alveolar Sat PC pool size was the sole factor contributing to change in tissue hysteresivity. No changes were observed in airway resistance. Despite the complex cascade of events initiated by antenatal endotoxin exposure, variability in lung tissue mechanics is associated primarily with changes in alveolar Sat PC pool and lung morphology.

fetal organ maturity; lung compliance; oscillometry; respiratory mechanics

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