Airway structure, function and development in health and disease

Abstract

Until they are fully mature, the airways are highly susceptible to damage. Factors that may contribute to vulnerability of immature airways and the occurrence of bronchopulmonary dysplasia (BPD) in preterm neonates include decreased contractility of smooth muscles of the airway, which leads to generation of lower forces, and immaturity of airway cartilage, leading to increased compressibility of developing airways. Mechanical ventilation has little effect on adult airways, but affects the dimensions and mechanical properties of preterm and newborn airways. Techniques for clinical evaluation of airway function include: (i). measurements of airway function during tidal breathing (airway resistance and reactivity are significantly elevated in infants with BPD); (ii). forced expiratory flow measurements [small-airway obstruction in infants with BPD is indicated by markedly reduced maximal volume measurements (Vmax)]; (iii). radiography procedures (plain radiographs, fluoroscopy, computed tomography and virtual bronchoscopy); and (iv). endoscopy procedures (rigid or flexible bronchoscopy, with or without measurement of oesophageal pressure). Imaging has demonstrated an excessively decreased airway cross-sectional area during exhalation in infants with BPD and acquired tracheomegaly in very preterm infants who had received mechanical ventilatory support. To further advance our understanding of how the airways develop, and to design less damaging protocols for mechanical ventilation in preterm neonates, basic laboratory studies of airway ultrastructure need to be performed and the results correlated with clinical pulmonary function studies.

Short-Term Mechanical Ventilation Increases Airway Reactivity in Rat Pups

“…The study represents a potentially important model to investigate the mechanisms involved in airway hyperreactivity induced by neonatal lung injury, and the data support the concept that exposure to mechanical ventilation during a critical period of lung development contributes to pulmonary morbidity in the premature infant (11). Preterm infants with BPD exhibit increased airway contractile responsiveness both acutely and as a long-term sequela of their disease (2,12). Although compromised airway function is most pronounced in children with a history of BPD (1), increased bronchial responsiveness is also common in prematurely born school-age children in the absence of BPD.…”

Chest Physical Therapy in Acute Viral Bronchiolitis: An Updated Review

“…Goblet cells hyperplasia develops, with excessive mucus production, resulting in narrowing or occlusion of the smaller airways, with ventilation dysfunction. 11,12 Repeated episodes of bronchoconstriction may also lead to structural changes in the walls of the small airways, known as remodeling. 13 …”

Longitudinal quantification of growth and changes in primary tracheobronchomalacia sites in children

“…2,17,18 The current understanding of TBM is that the loss of CSA of the lumen contributes to most symptoms and signs. 4,19,20 However, there are no data on the longitudinal changes in CSA of TBM disorders.…”