Developmental Changes in Tracheal Structure
003 1-3998/91/3002-0170$03.00/0 PEDIATRIC RESEARCH Vol. 30, No. 2, 199 1 Copyright O 1991 International Pediatric Research Foundation, Inc. Printed in U.S. A. Developmental Changes in Tracheal Structure KIRAN S. DEORAS, MARLA R. WOLFSON, ROBERT L. SEARLS, S. ROBERT HILFER, AND THOMAS H. SHAFFER Departments of Physiology and Pediatrics, Temple University School of Medicine, Department of Biology, Temple University, Philadelphia, Pennsylvania 19140 ABSTRACT. Mechanical properties of the proximal air- in tracheal structure parallel developmental differences in tra- ways are known to change with development; the highly cheal functional characteristics, we examined tracheal structure compliant airways of the immature animal become stiffer over a range of development from 70% of gestation to the and less collapsible with increasing age. Although the neonatal period. Anatomic, morphometric, and histochemical relationship between tracheobronchial architecture and techniques were used to study and quantify tracheal structural function has been described for adult physiology, little is characteristics from preterm and full-term newborn lambs. Cor- known regarding this relationship during early develop- relation of these findings with existing information on tracheal ment. This study was, therefore, designed to test the hy- mechanics may aid in understanding how the premature infant pothesis that alterations in tracheal morphometry parallel differs from the full-term neonate with regard to airway structure developmentaldifferences in tracheal functional properties. function. Tracheal segments obtained from 29 lambs ranging in age from 70% of gestation to full-term newborn lambs up to 6 MATERIALS AND METHODS d old were examined using anatomic, morphometric, and histochemical techniques. The results showed 1) progres- Tracheal segments (2-3 cm in length) were obtained from 2 1 sive increases in the dimensions of the trachea and the preterm lambs, 105 to 145 d gestational age (term, 147 +.
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