Effects of childhood respiratory diseases on the anatomical and functional development of the respiratory system

Development of airway function relative to lung growth in adolescent boys and girls from a general population, with and without mild respiratory symptoms. MEF_80%TLC, MEF_60%TLC and MEF_40%TLC are the forced expiratory flows at 80%, 60% and 40% of the total lung capacity (TLC) remaining in the lungs, respectively, which are used as measures of the patency of the large, intermediate and small airways. Airway function in children with and without respiratory symptoms grow in parallel without any signs of catch-up growth. (Reproduced with permission from ref. 11.)

Schematic individual development and decline of lung function in different circumstances. (a) Normal pattern (healthy subject); (b) progressive disease, presenting in adulthood; (c) impaired airway function in childhood and adulthood as a result of stable (“controlled”) lung disease or congenitally small airways; and (d) progressive disease, commencing in childhood, with an accelerated decline in adulthood. FEV₁, forced expiratory volume in 1second.

Discrepancy between the lung function test (normal flow–volume curve) and the high-resolution computed tomography scan of the thorax of an adolescent boy with cystic fibrosis showing bronchiectasis in both lower lobes (arrows). (Courtesy of H.A.W.M. Tiddens.)

Patterns of injury and repair following viral insults to the lung. (Reproduced with permission from ref. 124.)