Alveolarization Continues during Childhood and Adolescence: New Evidence from Helium-3 Magnetic Resonance

作者：Manjith Narayanan, J. R. Owers-Bradley, Caroline Beardsmore, Marius Mada, Iain Ball, Ruslan Garipov, Kuldeep Panesar, Claudia E. Kuehni, Ben D. Spycher, Siân E. Williams, Michael Silverman · 发表于：American Journal of Respiratory and Critical Care Medicine · 年份：2011 · DOI：10.1164/rccm.201107-1348oc · 被引用次数：294 · 研究领域：Neonatal Respiratory Health Research、Chronic Obstructive Pulmonary Disease (COPD) Research、Inhalation and Respiratory Drug Delivery

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 neoalveola...