Effects of Birth Asphyxia on the Modulation of Pharyngeal Provocation-Induced Adaptive Reflexes

Perinatal asphyxia and aerodigestive symptoms are troublesome. We tested the hypothesis that pharyngeal provocation alters proximal and distal aerodigestive reflex coordination and kinetics in infants with hypoxic ischemic encephalopathy (HIE), compared with healthy controls. Specifically, we characterized the sensory-motor properties of pharyngeal provocation-induced effects on upper esophageal sphincter (UES) and lower esophageal sphincter (LES) reflexes. Ten orally fed controls (32.0 ± 1.5 wk gestation) and 25 infants with HIE (38.1 ± 0.4 wk gestation) were evaluated at 39.7 ± 0.9 and 41.9 ± 0.6 wk postmenstrual age respectively. Pharyngo-esophageal reflexes evoked upon graded water stimuli were tested using water-perfusion micromanometry methods. Analysis included sensory-motor characteristics of pharyngeal reflexive swallow (PRS), pharyngo-UES-contractile reflex (PUCR), esophageal body-waveform kinetics, and pharyngo-LES-relaxation reflex (PLESRR). For controls vs. infants with HIE, median appearance, pulse, grimace, activity, respiration (APGAR) scores were 6 vs. 1 at 1 min ( P < 0.001) and 8 vs. 3 at 5 min ( P < 0.001). Upon pharyngeal- stimulation, HIE infants (vs. controls) had frequent PUCR ( P = 0.01); increased UES basal tone ( P = 0.03); decreased LES basal tone ( P = 0.002); increased pharyngeal-waveforms per stimulus ( P = 0.03); decreased frequency of LES relaxation ( P = 0.003); and decreased proximal esophageal contractile amplitude ( P = 0.002), with prolonged proximal esophageal contractile duration ( P = 0.008). Increased tonicity and reactivity of the UES and dysregulation of LES may provide the pathophysiological basis for pooling of secretions, improper bolus clearance, and aspiration risk. Deficits in function at the nuclear or supranuclear level involving glossopharyngeal and vagal neural networks and respiratory regulatory pathways involved with aerodigestive protection may be contributory.