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For the pediatrician, it is important to understand lung growth and development in order to properly diagnose and treat children for whom both may have gone wrong. It is crucial to the development of new diagnostic and treatment choices. This chapter will highlight the components of the developing lung, the factors that regulate their interaction, and the effects on pulmonary function in children.

Growth of the lung postnatally during infancy and childhood has typically been described in terms of the subdivision of alveoli, which accompanies the lengthening and widening of conducting airways, along with the vascular supplies for the growing bronchi and lung parenchyma.1 Investigations using animal models of mammalian lung development and disease increasingly reveal a dynamic process of lung cell turnover, repair, and regeneration with particular windows of vulnerability which will be important to pediatricians. Disrupted lung growth in early childhood has lifelong effects on lung function.2

Students and trainees of recent vintage will doubtless have been introduced to the “Barker hypothesis,” which describes a relationship between early life events and the susceptibility to acquired disease states in adulthood. Cohort studies from England describing study subjects born 70 to 80 years ago linked the diagnosis of pneumonia before age 2 years with substantial decrements in lung function (forced expiratory volume in 1 second, abbreviated FEV1) adjusted for age and height.3 More recent reports from a similarly designed larger cohort study from England failed to demonstrate a significant association between childhood “chest diseases” such as asthma, pneumonia, and whooping cough, and an accelerated rate of decline in lung function, so the role of childhood lung infection and lung growth on later adult pulmonary function is not yet clear.4

On the other hand, premature birth, arguably a disruption of lung development at an early vulnerable period, is associated with impaired lung function in later childhood and the adult years, with significant effects on forced expiratory flows and wheezing. Structural changes in lung parenchyma observed in chest-computed tomography scans of adults who were born prematurely are common, but their functional significance is unclear.5 Disrupted alveolar development or altered capacities of repair that occur in early childhood may lower the threshold at which chronic age-related pulmonary diseases are manifested, as depicted in eFigure 502.1. Improved understanding of the interactions of normal lung growth and environmental exposures will be indispensable to pediatricians now and in the future who seek to protect and preserve the function of the lung with its vulnerable interface with the “outside world.”

eFigure 502.1.

Insults to developing alveoli or airways early in childhood can decrease the age at which an individual reaches a disease “threshold,” when lung function has declined sufficient for symptoms to develop.

(Adapted with permission from Landrigan PJ, Sonawane B, Butler RN, et al. Early environmental origins of neurodegenerative disease in later life. ...

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