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
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
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