Autori: Manjith Narayanan, John Owers-Bradley, Caroline S Beardsmore, Marius Mada, Iain Ball, Ruslan Garipov, Kuldeep S Panesar, Claudia E Kuehni, Ben D Spycher, Sian E Williams, Michael Silverman

Editorial: Am J Respir Crit Care Med. , 2011.

Rezumat:

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 re-examined the current hypothesis using helium-3 ((3)He) magnetic resonance (MR) to assess alveolar size non-invasively between 7-21 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 functional residual capacity (FRC) (N=109) and average diffusion distance of helium (Xrms) 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.
RESULTS:
ADC increased by 0.19% for every 1% increment in FRC (95%CI: 0.13-0.25), whereas the expected change in the absence of neo-alveolarization is 0.41% (95%CI: 0.31-0.52). Similarly, increase of Xrms with FRC was significantly less than the predicted increase in the absence of neo-alveolarization. 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 neo-alveolarization 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.

Cuvinte cheie: Growth and Development, lung development, alveolarization, hyperpolarized 3He, Magnetic resonance imaging