Chapter 3 Apnea
PATHOPHYSIOLOGY
Apnea is the cessation of respiration for more than 20 seconds with or without cyanosis, hypotonia, or bradycardia. Apnea may be a symptom of another disorder that resolves when the latter is treated. Such disorders may include infection, gastroesophageal reflux, hypoglycemia, metabolic disorders, drug toxicity, or hydrocephalus, or thermal instability in newborns. Central apnea is a respiratory pause, the cause of which is related to the failure of the excitatory mechanisms to function properly in the respiratory center in the brain. Immaturity of the central nervous system frequently accounts for apnea of the newborn, which occurs most frequently during active sleep. Obstructive apnea occurs when an obstruction of the airway exists, usually at the level of the pharynx, and occurs most frequently during sleep. Here, there is continuation of respiratory effort without air flow in the airway because of the obstruction. This condition may be due to enlarged tonsils and adenoids, congenital disorders such as Pierre Robin syndrome, or muscular hypotonia. Apnea consisting of both central and obstructive components is mixed apnea. Apnea can also occur in premature infants during certain normal activities, such as feeding.
INCIDENCE
1. More than 50% of infants weighing less than 1.5 kg require treatment for recurrent prolonged apneic episodes.
2. About one third of infants born at less than 32 weeks’ gestation have apneic episodes.
3. Idiopathic apnea rarely occurs in term infants.
4. The prevalence of obstructive sleep apnea is estimated at 1% to 3% of preschool- and school-aged children. Obstructive apnea is most often caused by hypertrophy of the adenoids and tonsils.
