AP Ch 37 PDF - Respiratory Disorders in Infants and Children

## SUMMARY REVIEW ### Structure and Function - The airways of infants and children are narrower than those of adults, thus making them more prone to obstruction. - Infants and young children continue to form new alveoli for several years after birth. - Surfactant production is an important marker of...

## SUMMARY REVIEW ### Structure and Function - The airways of infants and children are narrower than those of adults, thus making them more prone to obstruction. - Infants and young children continue to form new alveoli for several years after birth. - Surfactant production is an important marker of developmental maturity of the fetal lung and is secreted into the airways by 30 weeks' gestation. - The immature chest wall is soft and compliant, contributing to inefficient mechanisms of breathing. - Children have greater oxygen consumption than adults per unit of body weight. - Immune mechanisms are not fully developed at birth, making young infants more susceptible to infection. - Newborns have a blunted ventilatory response to hypoxia compared with older children and adults, increasing their risk for apnea and hypoxemia. - Neonatal exposure to air pollution increases the risk for respiratory disease. ### Disorders of the Upper Airways - Physical examination can provide important clues in assessing the location and nature of UAO and stridor. - Upper airway infections can pose serious threats because of inflammatory edema and airway obstruction, including bacterial tracheitis, retropharyngeal abscess, and peritonsillar infections. Recognition and rapid evaluation are crucial. - Viral croup (laryngotracheobronchitis) is the most common cause of acute upper airway inflammatory obstruction in children ages 6 months to 5 years. Subglottic edema may be mild to severe. Parainfluenza is the most common cause. - Acute epiglottitis is a life-threatening emergency that is now rarely seen because of vaccination against _H. influenzae_, which had been the primary causative microorganism. Current cases usually represent vaccine failure or are caused by other bacteria, such as group A streptococci. - Tonsillar infections may be severe enough to cause UAO, and they are treated with appropriate antibiotics and corticosteroids. Complications can include tonsillar abscess. - Bacterial tracheitis causes airway edema and copious purulent secretions with UAO and requires administration of antibiotics and maintenance of the airway. - Retropharyngeal abscess is associated with nasopharyngeal infection or penetrating local injury and requires immediate antibiotic treatment. - Aspiration of a foreign body should be considered whenever there is a sudden onset of stridor, coughing, wheezing, or hoarseness. This usually occurs in children ages 1 to 3 years. Occasionally diagnosis is delayed and symptoms may be attributed to asthma, bronchitis, or pneumonia without recognition of the underlying cause. - Angioedema is a mast cell-mediated allergy to certain foods, causing edema of mucous membranes or subcutaneous layers of the skin; it can result in mucosal swelling and airway obstruction. - Chronic UAO may be manifested by stridor, abnormal cry, wheezing, or dyspnea. Causes of stridor in infants include laryngomalacia, tracheomalacia, subglottic stenosis, laryngeal atresias, tracheal stenosis, vocal cord paralysis, and vascular rings. - Obstructive sleep apnea syndrome usually occurs in older children rather than infants and is underdiagnosed. Typical symptoms are related to airway narrowing and include snoring, gasping, and restless sleep. OSAS is associated with airway narrowing and increased upper airway collapsibility. Adenotonsillar hypertrophy, gastroesophageal reflux, obesity, and craniofacial anomalies are common causes of OSAS. ### Disorders of the Lower Airways 1. SDD (RDS) of the newborn usually occurs in premature infants who are born before surfactant production and alveolocapillary development are complete. Atelectasis and hypoventilation cause shunting, hypoxemia, and hypercapnia. 2. BPD is a chronic lung disease of infancy that is usually the consequence of acute respiratory disease in premature infants who required oxygen and positive pressure ventilatory support. Contributing factors include structural immaturity, inflammation, and disordered lung repair processes. 3. Bronchiolitis occurs in infants and toddlers, usually in the winter and early spring. It is caused by viruses, most commonly RSV. There is extensive edema, inflammation, and damage to the bronchiolar epithelium with airway obstruction and wheezing. Injection of monoclonal antibody against RSV or immunotherapy is recommended as a preventive measure for high-risk infants. 4. Childhood pneumonia is infection and inflammation in the terminal airways and alveoli usually caused by community-acquired viruses (most common), bacteria, or _Mycoplasma_. Lobar pneumonia is usually bacterial. Certain bacteria, such as _S. aureus_ and group A streptococci, can cause particularly fulminant disease, as well as abscesses and empyema. 5. Aspiration pneumonitis can occur because of lung inflammation from entry of any foreign substance, including food, drink, or chemicals. Aspiration of oropharyngeal bacteria can occur because of loss of protective reflexes in neurologically impaired children, or during induction of anesthesia. 6. Bronchiolitis obliterans is fibrotic obstruction of the respiratory bronchioles and alveolar ducts usually secondary to severe respiratory viral infection or graft-versus-host disease after allograft transplantation. It is rare in children. 7. Asthma is a chronic inflammatory disease characterized by bronchial hyperreactivity and reversible airflow obstruction; it usually occurs in response to an allergen and has episodes of acute respiratory symptoms (cough, wheeze, dyspnea) and intermittent or chronic subacute symptoms. It is the most common chronic condition in children and results from genetic susceptibility and environmental factors with varying phenotypes. Environmental triggers cause inflammatory cell infiltration, mucosal edema, mucus plugging of airways, and epithelial damage with obstruction to airflow and long-term remodeling of airways. 8. ARDS is an acute life-threatening condition characterized by severe hypoxemia, poor lung compliance, atelectasis, and diffuse densities on chest radiographs. It can be triggered by direct acute lung injury (ALI), such as pneumonia, aspiration, near drowning, or smoke inhalation; or from a systemic insult, such as sepsis or multiple trauma. High-level ventilatory support is required, and mortality is significant. 9. CF is an autosomal recessive disease caused by the cystic fibrosis transmembrane conductance regulator (CFTR) gene mutation. Defective chloride secretion and excess sodium absorption cause production of thick, tenacious mucus, plugging of airways, chronic pulmonary infection, and bronchiectasis related to airway epithelial chloride and sodium transport. The other major manifestations are digestive and nutritional, related to pancreatic insufficiency. ### Sudden Infant Death Syndrome 1. SIDS is a diagnosis of exclusion after thorough investigation and autopsy following sudden death of an infant younger than 1 year of age. Usually the event occurs during nighttime sleep. 2. The cause is unknown. However, some known risk factors are avoidable, such as maternal smoking, prone sleeping, using soft bedding surfaces, and overheating of the infant. The incidence of SIDS has decreased significantly since public health campaigns have encouraged the supine sleeping position for babies.