Neonatal hyperoxia up regulates cough reflex in young rabbits

Abstract

A link between cough in childhood and neonatal exposure to hyperoxia following preterm birth has been suggested. The hypothesis is tested that neonatal exposure to hyperoxia is associated with long term up regulation of cough. Airway hyperresponsiveness is also investigated because it is a frequent finding in children born preterm and may be linked to cough. Thirty nine young rabbits survived a 48 h neonatal exposure to 93% oxygen (H, n=26) or continued room air (A, n=13). Cough response to mechanical tracheal stimulation and airway responses to a mock exercise and to methacholine were studied under anaesthesia. Larger incidence of coughs and increased sensitivity to tracheal stimulation occurred in H vs A (p<0.01), while bronchial responses to exercise or methacholine were similar in both groups. Neonatal hyperoxia is associated with up regulation of cough in young rabbits. The lack of a parallel increase in airway responsiveness suggests up regulation may be of central origin.

Keywords: Cough; Direct airway responsiveness; Hyperoxia; Indirect airway responsiveness; Newborn.