Background
Aspiration syndromes include all conditions in which foreign substances are inhaled into the lungs. Most commonly, aspiration syndromes involve oral or gastric contents associated with gastroesophageal reflux (GER), swallowing dysfunction, neurological disorders, and structural abnormalities. The volume of refluxate may be significant, usually causing acute symptoms associated with the penetration of gastric contents into airways, or there may be episodic incidents of small amounts of oral or gastric reflux or saliva that enter the airways causing intermittent or persistent symptoms.
GER is very common in infants and children and has been associated with a spectrum of pediatric problems; however, the percentage of reflux that causes respiratory complications is unknown. In 1912, Sir William Osler described the relationship between asthma and GER by stating that “attacks may be due to direct irritation of the bronchial mucosa or… indirectly, too, by reflex influences from stomach.” Recent literature describes GER and aspiration syndromes as common occurrences with increasing diagnostic rates. Swallowing dysfunction in conjunction with GER is more likely to cause respiratory symptoms than GER symptoms alone. Eosinophilic GI disorders (eg, eosinophilic esophagitis, gastroenteritis) may also manifest similarly to GER but are refractory to traditional reflux therapies.
Joint clinical practice guidelines for evaluation and treatment of GER in infants and children have been developed by The North American Society for Pediatric Gastroenterology, Hepatology, and Nutrition (NASPGHAN) and the European Society for Pediatric Gastroenterology, Hepatology, and Nutrition (ESPGHAN).
Swallowing dysfunction is a known etiology of aspiration in children. Divided into 4 distinct phases, swallowing is a complex action that involves 5 cranial nerves and 26 muscles. The mouth, pharynx, larynx, and esophagus are involved in a coordinated effort to induce swallowing. Any anatomic, neurologic, or physiologic defect in the swallowing mechanism during the preparatory, oral, pharyngeal, or esophageal phases may lead to aspiration.
Cricopharyngeal dysfunction, cricopharyngeal incoordination of infancy, and transient pharyngeal muscle dysfunction are well described in the pediatric literature. Cricopharyngeal dysfunction involves cricopharyngeal muscle spasm or achalasia of the superior esophageal sphincter. Cricopharyngeal incoordination of infancy is noted in infants who have a normal suck reflex but have incoordination during swallowing; this is possibly secondary to delayed maturation of swallowing reflexes or may be associated with cerebral palsy.
Neurological disorders, including congenital and progressive diseases, may manifest as aspiration syndromes in infants and children. Isolated superior laryngeal nerve damage, vocal cord paralysis, cerebral palsy, muscular dystrophy, and Riley-Day syndrome (ie, familial dysautonomia) are a few of the neurological disorders associated with increased risk of aspiration.
Anatomic disorders, such as cleft palate, laryngeal cleft, esophageal atresia, tracheoesophageal fistula, duodenal obstruction, or malrotation, may have associated aspiration risk. Other conditions such as macroglossia, micrognathia, and laryngeal cleft may predispose patients to aspiration. Motility disorders, such as achalasia or connective-tissue disorders, are associated with increased risk of aspiration.