Hering-Breuer reflex and sleep state in the preterm infant

Hering-Breuer reflex, lung volume and position in prematurely born infants

OBJECTIVES

To investigate the effect of position on the strength of the Hering-Breuer reflex in prematurely born infants and determine whether any differences seen were related to differences in lung or tidal volume between positions.

WORKING HYPOTHESIS

Position related differences in the strength of the Hering-Breuer reflex relate to differences in lung or tidal volume.

STUDY DESIGN

Prospective observational study. PATIENT/SUBJECT SELECTION: Eighteen infants, median gestational age 30 (range 25-32) weeks were studied.

METHODOLOGY

Infants were examined in the supine and prone position, each position was maintained for 2 hr. At the end of each 2-hr period, the strength of the Hering-Breuer reflex was assessed by determining the prolongation of expiration following an end inspiratory occlusion. In addition, tidal volume and functional residual capacity (FRC) were assessed in each position.

RESULTS

The strength of the Hering-Breuer reflex was greater (P = 0.01) and the mean FRC was higher (P < 0.0001) in the prone compared to the supine position. The position related differences in the strength of the reflex correlated significantly with position related differences in FRC (P = 0.05).

CONCLUSIONS

The Hering-Breuer reflex is stronger in the prone compared to the supine position. Our results suggest this is explained by position related differences in lung volume.

The effects of positioning on the Hering-Breuer reflex in the preterm infant

The aim of this study was to determine the effect of positioning on the Hering-Breuer inflation reflex (HBIR) in the preterm infant. Seven, non-intubated, premature infants, ranging in birthweight from 732 to 1450 g with post-conceptual ages of 32-36 weeks were studied. In each infant, pulmonary function testing, including the HBIR was obtained using the SensorMedics 2600 during quiet sleep in the supine and prone position. The strength of the HBIR 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 the prone position versus the supine position with a consistently stronger reflex in the prone position. The mean percent prolongation of expiration was 237 +/- 108% in the prone position versus 95 +/- 32% in the supine position. Analysis of the data, using paired t-testing revealed a mean difference of 142 +/- 119% between prone and supine positions (P=0.028). Significant differences in the strength of the HBIR occur in relation to positioning in the preterm infant. Newborn positioning may affect pulmonary reflexes and may play a role in control of breathing.

Lung-function tests in neonates and infants with chronic lung disease: tidal breathing and respiratory control

This paper is the fourth in a series of reviews that will summarize available data and critically discuss the potential role of lung-function testing in infants with acute neonatal respiratory disorders and chronic lung disease of infancy. The current paper addresses information derived from tidal breathing measurements within the framework outlined in the introductory paper of this series, with particular reference to how these measurements inform on control of breathing. Infants with acute and chronic respiratory illness demonstrate differences in tidal breathing and its control that are of clinical consequence and can be measured objectively. The increased incidence of significant apnea in preterm infants and infants with chronic lung disease, together with the reportedly increased risk of sudden unexplained death within the latter group, suggests that control of breathing is affected by both maturation and disease. Clinical observations are supported by formal comparison of tidal breathing parameters and control of breathing indices in the research setting.