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This Article Full Text Full Text (PDF) All Versions of this Article: 104/4/1167    most recent 00587.2007v1 Submit a response Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Bolle, I. Articles by Schulz, H. PubMed PubMed Citation Articles by Bolle, I. Articles by Schulz, H.

Postnatal lung function in the developing rat

¹Helmholtz Zentrum München German Research Center for Environmental Health, Institute for Inhalation Biology, Neuherberg/Munich, Germany; and ²Molecular and Integrative Physiological Sciences, Harvard School of Public Health, Boston, Massachusetts

Submitted 1 June 2007 ; accepted in final form 2 January 2008

Little is known about lung function during early stages of postnatal maturation, although the complex structural changes associated with developing rat lung are well studied. We therefore analyzed corresponding functional (lung volume, respiratory mechanics, intrapulmonary gas mixing, and gas exchange) and structural (alveolar surface area, mean linear intercept length, and alveolar septal thickness) changes of the developing rat lung at 7–90 days. Total lung capacity (TLC) increased from 1.54 ± 0.07 to 16.7 ± 2.46 (SD) ml in proportion to body weight, but an increase in body weight exceeded an increase in lung volume by almost twofold. Series dead space volume increased from 0.21 ± 0.03 to 1.38 ± 0.08 ml but decreased relative to TLC from 14% to 8%, indicating that parenchymal growth exceeded growth of conducting airways. Diffusing capacity of CO (DCO) increased from 8.1 ± 0.8 to 214.1 ± 23.5 µmol·min^–1·hPa^–1, corresponding to a substantial increase in surface area from 744 ± 20 to 6,536 ± 488 cm². DCO per unit of lung volume is considerably lower in the immature lung, inasmuch as DCO/TLC in 7-day-old rats was only 42% of that in adult (90 day-old) rats. In humans, however, infants and adults show comparable specific DCO. Our functional and structural analysis shows that gas exchange is limited in the immature rat lung. The pivotal step for improvement of gas exchange occurs with the transition from bulk alveolarization to the phase of expansion of air spaces with septal reconstruction and microvascular maturation.

respiratory mechanics; dead space volume; intrapulmonary gas mixing; diffusing capacity