CARDIAC AND RESPIRATORY REACTIVITY TO GASTROESOPHAGEAL REFLUX - EXPERIMENTAL-DATA IN INFANTS

Gastroesophageal reflux associated with apnea and/or bradycardia induc es both dilatation of the esophagus and abrupt intrusion of acid conte nt in it. To evaluate the relative importance of these two types of st imulation on cardiac and respiratory responses, a series of experiment al protocols were designed, in which we evaluated the influence of eso phageal dilatation alone, acid infusion alone and both stimulations si multaneously. The passage of a volume in the lower third of the esopha gus (n = 14) during reflux was simulated by balloon dilatation; the pa ssage of acid gastric juice during reflux was simulated by an esophage al acid infusion test, within the physiological range (n = 8; duration = 5 min; pH = 2.2). Cardiac, respiratory and arousal responses were c ompared during a control period and during the distal balloon dilatati on and esophageal saline and acid infusion periods. Distal esophageal balloon dilatation and acid infusion induced significant prolongation of the RR interval and of the duration of the respiratory cycle. The p resence of the esophageal catheter did not lead to continuous vagal st imulation. Simultaneous stimulation by balloon dilatation and acid inf usion provoked cardiac responses that were above the level reached by each stimulation separately. Behavioral and electroencephalographic ob servations demonstrate significantly more frequent and longer arousal responses during the acid infusion than during control and saline infu sion periods. We conclude that distal esophageal balloon dilatation an d acid infusion elicit significant cardiac and respiratory responses i n newborns during active sleep. Since arousal from sleep has been show n to facilitate esophageal clearance, we speculate that arousal respon ses, observed only during acid infusion, may be one of the defence mec hanisms related to acid gastroesophageal reflux.