Respiratory mechanics and lung development in the rat from early age to adulthood.
Gomes, R. F. M., F. Shardonofsky, D. H. Eidelman, and J. H. T. Bates.
1Meakins-Christie Laboratories, McGill University, Montréal, Québec, Canada, H2X 2P2; 2Texas Children's Hospital, Houston, Texas 77030; and 3Vermont Lung Center, Department of Medicine, University of Vermont, Burlington, Vermont 05446
APStracts 8:0056A, 2001.
The purpose of the present study was to establish how the dependence of respiratory mechanics on lung inflation changes during development. We studied seven groups of rats from 10 days to 3 mo of age at five levels of positive end-expiratory pressure (PEEP) from 0 to 7 hPa (1 hPa = 0.1 kPa ˜ 1 cmH2O). At each PEEP level, we measured respiratory system resistance and elastance at both 0.9 and 4.8 Hz to partition the mechanical properties into its airway and tissue components. Elastance increased more rapidly with PEEP in the younger animals, which we interpret as reflecting a more pronounced strain stiffening of the younger parenchyma. However, the decrease in airway resistance with PEEP was more pronounced in the older animals. Morphometric analysis showed that mean tissue density decreased and total alveolar surface area increased with age. Our data suggest that the mechanical interdependence between airways and parenchyma is weaker in very young animals compared with mature animals. This may play a role in the hyperresponsiveness of immaturity.
Received 2 September 2000; accepted in final form 27 November 2000
APS Manuscript Number A896-0.
Article publication pending J Appl Physiol
ISSN 1080-4757 Copyright 2001 The American Physiological Society.
Published in APStracts on 29 January 2001