Motor activity and apnea in preterm infants. Is there a causal relationship?

It is generally believed that all apneic episodes in preterm infants occur during sleep. Because occurrence of apnea during wakefulness has been documented in these infants, we investigated its frequency and characteristics in 10 premature infants using simultaneous polygraphic and video recordings. Behavioral arousal with motor activity preceded the onset of apnea in 202 episodes. Approximately 60% of episodes began within 15 s of arousal. Whereas most of the episodes were short and asymptomatic, hypoxia and/or bradycardia developed during 18 apneic spells, and these episodes accounted for a third of all apneic episodes that resulted in bradycardia or hypoxia in these infants studied. Essentially, all movement-related apneas (17 of 18) began within 15 s of arousal; motor activity continued throughout apnea in 13, whereas apnea resolved after cessation of motor activity in the remaining five. The main finding of the present study is that movement-related apnea is far more frequent than previously recognized. This finding is important in the clinical management of preterm infants with apnea.