A comparison of swallowing during apnea and periodic breathing in premature infants.

Periodic breathing and apnea are two forms of ventilatory instability which are commonly observed in premature infants. This study was undertaken to characterize the pattern of swallowing during apnea and compare this pattern to that present during breathing. We assessed the frequency and distribution of swallows during the respiratory pauses of apnea and periodic breathing in 22 premature infants birth weight 1.2 +/- 0.2 kg, postconceptional age 34 +/- 2 wk. Twelve infants had apnea and 10 exhibited periodic breathing. During sleep the pharyngeal phase of swallowing was detected by a catheter in the pharynx and esophageal peristalsis by an esophageal pressure catheter. Nasal airflow was monitored by a pneumotachometer. During apnea, the frequency of swallows was significantly greater than during the respiratory pauses of periodic breathing (15.9 +/- 8.2 versus 0.72 +/- 0.73 swallows/min, respectively, p < 0.0001) and also much higher than the rate of spontaneous swallows during sleep in either group (0.66 +/- 0.66 and 0.58 +/- 1.08 swallows/min, respectively). We conclude that an increased rate of swallowing is characteristic of apnea in premature infants, and distinguishes apnea from the respiratory pauses of periodic breathing.