Apnea of prematurity

Apnea of prematurity is defined as cessation of breathing by a premature infant that lasts for more than 20 seconds and/or is accompanied by hypoxia or bradycardia. Apnea is traditionally classified as either obstructive, central, or mixed. Obstructive apnea may occur when the infant's neck is hyperflexed or conversely, hyperextended. It may also occur due to low pharyngeal muscle tone or to inflammation of the soft tissues, which can block the flow of air though the pharynx and vocal cords. Central apnea occurs when there is a lack of respiratory effort. This may result from central nervous system immaturity, or from the effects of medications or illness. Many episodes of apnea of prematurity may start as either obstructive or central, but then involve elements of both, becoming mixed in nature. Ventilatory drive is primarily dependent on response to increased levels of carbon dioxide (CO2) and acid in the blood. A secondary stimulus is hypoxia. Responses to these stimuli are impaired in premature infants due to immaturity of specialized regions of the brain that sense these changes. In addition, premature infants have an exaggerated response to laryngeal stimulation (a normal reflex that closes the airway as a protective measure). Apnea of prematurity can be readily identified from other forms of infant apnea such as obstructive apnea, hypoventilation syndromes, breathing regulation issues during feeding, and reflux associated apnea with an infant pneumogram or infant apnea/sleep study. It has been reported that the incidence of neonatal apnea happens in almost all infants with gestational age of less than 29 weeks or the birth weight of less than 1000g. Methylxanthines (theophylline and caffeine) have been used for almost three decades to treat apnea of prematurity. Despite this prevalent use, there are concerns of long term negative effects from the use of caffeine. Caffeine and theophylline have similar short-term effects on apnea, but theophylline is associated with higher rates of toxicity.