Hering-Breuer reflex and sleep state in the preterm infant.

The aim of this study was to determine the effect of sleep state on the Hering-Breuer inflation reflex in the preterm infant. Seventeen nonintubated, premature infants, ranging in birth weight from 980-2,440 g with postconceptual ages of 30-36 weeks, were studied. In each infant, pulmonary function testing, including the Hering-Breuer inflation reflex, was obtained using the SensorMedics 2600 during active and quiet sleep states in supine position. The strength of the Hering-Breuer inflation reflex was quantified by the measurement of the percent prolongation of expiration after an occluded breath. Sleep states were categorized by the criteria of Prechtl. There was a significant difference in Hering-Breuer activity in active (REM) vs. quiet (non-REM) sleep, with a consistently stronger reflex in the active sleep state. The mean percent prolongation of expiration was 419% in active sleep vs. 87% in quiet sleep. Analysis of the data, using a paired t-test, revealed a mean difference of 331 +/- 185% between active and quiet sleep (P = 0.000). In conclusion, significant differences in the strength of the Hering-Breuer inflation reflex occur in relation to sleep state, and may explain the variability of the reflex described in previous studies. Measurement of the Hering-Breuer inflation reflex may be affected by pulmonary stretch receptors as well as chest wall afferents in the preterm infant.