DEFINITION :

Apnea is the most common problem of ventilatory control in the premature infant frequently prolonging hospitalization and needing cardiopulmonary monitoring. The standard definition of apnea is cessation of inspiratory gas flow for 20 seconds, or for a shorter period of time if accompanied by bradycardia (heart rate less than 100 beats per minute), cyanosis, or pallor.

This must be distinguished from periodic breathing which is three or more respiratory pauses of greater than 3 seconds duration with less than 20 seconds respiration between the pauses. Such a pattern generally unaccompanied by hypoxemia is thought to be benign.

TYPES :

Apnea has been classified into three types depending on whether inspiratory muscle activity is present. If inspiratory muscle activity fails following an exhalation, it is termed Central Apnea. If inspiratory muscle activity is present without airflow, this is termed Obstructive Apnea. If both central and obstructive apnea occurs during the same episode, this is termed Mixed Apnea. It is important to characterize a patient's apnea episodes into one or more types for treatment consideration.

INCIDENCE :

Although there is considerable variation in incidence and severity of apnea in premature infants, both are inversely related to gestational age. Approximately 50% of infants less than 1500 grams birth weight require either pharmacologic intervention or ventilatory support for recurrent prolonged apneic episodes. The peak incidence occurs between 5 and 7 days postnatal age. Apnea of Prematurity is a specific diagnosis and usually resolves between 34 to 36 weeks postconceptual age.

The incidence of apnea and periodic breathing in the term infant has not been adequately determined. Approximately 50-60% of preterm infants have evidence of apnea: 35% present with central apnea, 5-10% with obstructive apnea, 15-20% with mixed apnea. Another 30% will have periodic breathing. (1)