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.
(c) 2008 Wiley-Liss, Inc.