Chapter 30: Alterations of Pulmonary Function in Children

Upper airway disorders include viral croup, characterized by a distinctive barking cough and inspiratory stridor resulting from subglottic inflammation, as well as bacterial tracheitis, acute epiglottitis, and peritonsillar complications that require rapid clinical recognition and intervention. Foreign body aspiration remains a common pediatric emergency, particularly in toddlers, while obstructive sleep apnea syndrome in children typically stems from adenotonsillar enlargement, obesity, or anatomical abnormalities and can produce significant neurocognitive consequences if untreated. Lower airway pathology predominates in younger infants due to immature lung structure and function. Respiratory distress syndrome in newborns results from inadequate pulmonary surfactant, leading to alveolar collapse, hypoxemia, and systemic acidosis, with treatment focused on antenatal corticosteroid administration and exogenous surfactant replacement therapy. Bronchopulmonary dysplasia emerges as a chronic sequela of prolonged mechanical ventilation and oxygen exposure in premature infants, characterized by abnormal alveolar development and persistent respiratory compromise. Bronchiolitis, predominantly caused by respiratory syncytial virus, represents the most common lower respiratory infection requiring hospitalization in infancy and produces bronchiolar obstruction with widespread air trapping. Pneumonia in children involves diverse pathogens including viral, bacterial, and atypical organisms, while aspiration pneumonitis occurs when food, gastric contents, or foreign material damages pulmonary tissues. Childhood asthma, the most prevalent chronic disease in pediatric populations, results from genetic and environmental interactions producing airway hyperresponsiveness, reversible obstruction, and structural remodeling. Cystic fibrosis, caused by mutations in the cystic fibrosis transmembrane conductance regulator gene, leads to viscous secretions, chronic suppurative infection, bronchiectasis, and progressive respiratory failure despite emerging targeted molecular therapies. The chapter concludes by addressing sudden infant death syndrome, the leading cause of unexplained mortality in infants aged two to four months, with established risk factors including prone sleep positioning, soft sleep surfaces, maternal smoking, prematurity, and autonomic nervous system dysfunction.