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Am J Respir Crit Care Med. 2012 Jan 15;185(2):186-91. doi: 10.1164/rccm.201107-1348OC. Epub 2011 Oct 27.

Alveolarization continues during childhood and adolescence: new evidence from helium-3 magnetic resonance.

Author information

1
Department of Infection, Immunity and Inflammation, University of Leicester, United Kingdom. mn87@leicester.ac.uk

Abstract

RATIONALE:

The current hypothesis that human pulmonary alveolarization is complete by 3 years is contradicted by new evidence of alveolarization throughout adolescence in mammals.

OBJECTIVES:

We reexamined the current hypothesis using helium-3 ((3)He) magnetic resonance (MR) to assess alveolar size noninvasively between 7 and 21 years, during which lung volume nearly quadruples. If new alveolarization does not occur, alveolar size should increase to the same extent.

METHODS:

Lung volumes were measured by spirometry and plethysmography in 109 healthy subjects aged 7-21 years. Using (3)HeMR we determined two independent measures of peripheral airspace dimensions: apparent diffusion coefficient (ADC) of (3)He at FRC (n = 109), and average diffusion distance of helium (X(rms)) by q-space analysis (n = 46). We compared the change in these parameters with lung growth against a model of lung expansion with no new alveolarization.

MEASUREMENTS AND MAIN RESULTS:

ADC increased by 0.19% for every 1% increment in FRC (95% confidence interval [CI], 0.13-0.25), whereas the expected change in the absence of neoalveolarization is 0.41% (95% CI, 0.31-0.52). Similarly, increase of (X(rms)) with FRC was significantly less than the predicted increase in the absence of neoalveolarization. The number of alveoli is estimated to increase 1.94-fold (95% CI, 1.64-2.30) across the age range studied.

CONCLUSIONS:

Our observations are best explained by postulating that the lungs grow partly by neoalveolarization throughout childhood and adolescence. This has important implications: developing lungs have the potential to recover from early life insults and respond to emerging alveolar therapies. Conversely, drugs, diseases, or environmental exposures could adversely affect alveolarization throughout childhood.

PMID:
22071328
PMCID:
PMC3410735
DOI:
10.1164/rccm.201107-1348OC
[Indexed for MEDLINE]
Free PMC Article

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