科研之友
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摘要
Rationale: The current hypothesis that human pulmonary alveolarization is complete by 3 years is contradicted by new evidence of alveolarization throughout adolescence in mammals. %26lt;br%26gt;Objectives: We reexamined the current hypothesis using helium-3 (He-3) 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. %26lt;br%26gt;Methods: Lung volumes were measured by spirometry and plethysmography in 109 healthy subjects aged 7-21 years. Using (HeMR)-He-3 we determined two independent measures of peripheral airspace dimensions: apparent diffusion coefficient (ADC) of He-3 at FRC(n = 109), and average diffusion distance of helium ((X-rms) over bar) 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. %26lt;br%26gt;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) over bar) 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. %26lt;br%26gt;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.
- 出版日期2012-1-15
