OBJECTIVE Eating difficulties coupled with cardiorespiratory spells delay acquisition of feeding milestones in convalescing neonates, and the mechanisms are unclear . Aims were to examine and compare the pharyngoesophageal-cardiorespiratory (PECR) response characteristics: (a) in control neonates and those with recurrent bradycardia spells; and (b) during pharyngeal stimulation when bradycardia occurs versus when no bradycardia occurs .
METHODS Preterm infants (N = 40, 27 ± 3 weeks gestation), underwent concurrent pharyngoesophageal manometry, electrocardiography, respiratory inductance plethysmography, and nasal airflow thermistor to evaluate pharyngoesophageal motility, heart rate (HR), and respiration during graded abrupt pharyngeal sterile water stimuli . Infants with recurrent bradycardia (N = 28) and controls (N = 12) were evaluated at 38 (38-40) and 39 (38-40) weeks postmenstrual age, respectively . Comparisons were performed (a) between study and control groups; and (b) among HR responses of <80 BPM , 80-100 BPM, and> 100 BPM .
RESULTS Overall, characteristics of PECR responses in infants with a history of recurrent bradycardia (vs. controls) did not differ (p>.05). However, when pharyngeal stimulus induced severe bradycardia (< 80 BPM): prolonged respiratory rhythm change, increased pharyngeal activity, increased esophageal dysmotility (as evidenced by prolonged esophageal inhibition and motor activity), and prolonged lower esophageal sphincter relaxation were noted (all p <.05).
CONCLUSIONS In control infants and those with recurrent bradycardia, pharyngeal stimulation results in similar PECR response characteristics . However, when severe bradycardia occurs, PECR response characteristics are distinct . The mechanisms of severe bradycardia spells are related to abnormal prolongation of vagal inhibitory effects on cardiorespiratory rhythms in conjunction with prolonged esophageal inhibition and delays with terminal swallow.