Effect of maturation of the magnitude of mechanosensitive and chemosensitive reflexes in the premature human esophagus

Abstract

Objectives-To investigate the effect of esophageal mechanosensitive and chemosensitive stimulation on the magnitude and recruitment of peristaltic reflexes and upper esophageal sphincter (UES)-contractile reflex in premature infants.Study design-Esophageal manometry and provocation testing were performed in the same 18 neonates at 33 and 36 weeks postmenstrual age (PMA). Mechanoreceptor and chemoreceptor stimulation were performed using graded volumes of air, water, and apple juice (pH 3.7), respectively. The frequency and magnitude of the resulting esophago-deglutition response (EDR) or secondary peristalsis (SP), and esophago-UES-contractile reflex (EUCR) were quantified.Results-Threshold volumes to evoke EDR, SP, or EUCR were similar. The recruitment and magnitude of SP and EUCR increased with volume increments of air and water in either study (P < .05). However, apple juice infusions resulted in increased recruitment of EDR in the 33 weeks group (P < .05), and SP in the 36 weeks group (P < .05). The magnitude of EUCR was also volume responsive (all media, P < .05), and significant differences between media were noted (P < .05). At maximal stimulation (1 mL, all media), sensory-motor characteristics of peristaltic and EUCR reflexes were different (P < .05) between media and groups.Conclusions-Mechano-and chemosensitive stimuli evoke volume-dependent specific peristaltic and UES reflexes at 33 and 36 weeks PMA. The recruitment and magnitude of these reflexes are dependent on the physicochemical properties of the stimuli in healthy premature infants.Gastroesophageal reflux (GER) is frequent in neonates and infants, and its role in the cause of or association with neonatal morbidity including dysphagia, chronic lung disease, or apparent life-threatening events is not understood. 1,2,3 The mechanisms of GER disease are as well defined in neonates as in adults. 4 relaxation is the most common cause, but hypotonic LES and poor esophageal peristalsis are also described. 6,7 The refluxate (gas, liquid, or mixed contents) provokes esophageal distention or acidification, and it may trigger luminal clearance to provide aerodigestive safety. Clearance mechanisms including primary peristalsis (PP), secondary peristalsis (SP) and esophago-upper esophageal sphincter (UES)-contractile reflexes (EUCR) that may prevent the entry of refluxate into the pharynx or larynx are well recognized in healthy adults and those with GER disease. [8][9][10][11] Immaturity, rapid development, and changing feeding behavior distinctly separate evolving pathophysiology in neonates from that of older subjects.Aerodigestive symptoms may result from delayed clearance, airway aspiration, or chemoreceptor stimulation. 12-15 We described methods to evaluate the esophageal body and UES motor responses resulting from esophageal provocation. [16][17][18] In our previous studies, we validated the technique of esophageal afferent provocation using different media (air or liquids) and characterized the occurrence of esophago-deglutition response (E...

Esophageal sensation in premature human neonates: temporal relationships and implications of aerodigestive reflexes and electrocortical arousals

“…The use of esophageal manometry methods in neonates was described by us before (15,16,18). Briefly, the catheter assembly (Dentsleeve International, Mui Scientific, Mississauga, Ontario, Canada) was connected to the pneumohydraulic micromanometric water perfusion system via the resistors, pressure transducers (TNF-R disposable pressure transducers), and amplifiers (Solar modules, Solar 2, MMS medical instruments, Dover, NH).…”

“…Continuous data acquisition and analysis were performed during manometric study based on waveform characteristics, as defined before (15,16,18). During manometric pull-through, the high-pressure zones of the lower and upper esophageal sphincters (LES and UES, respectively) were identified by the presence of a consistent increase in pressure greater than 5.0 mmHg above the baseline for at least 15 s, in addition to the changes in pressure with respiration (15,16,18).…”

“…We have previously studied the effects of midesophageal sensory stimuli on esophageal peristaltic reflex and upper esophageal sphincter contractile reflex (UESCR) to divert visceral stimulus away from the aerodigestive tract in premature infants (15,18). Although spontaneous electrocortical arousals (ECAs) and somatic stimuli-induced arousals have been documented in sleep (36), recognition of cortical arousal as an effect of visceral stimulus during sleep is not well understood in premature neonates.…”

Maturation of upstream and downstream esophageal reflexes in human premature neonates: the role of sleep and awake states

“…Continuous data acquisition and analysis were performed during manometric study based on waveform characteristics, as previously defined (15,16,21). The high-pressure zones of the LES and UES were identified during manometric pull through by the consistent increase in pressure Ͼ5.0 mmHg above the baseline for at least 15 s, in addition to the changes in pressure with respiration (15,16,21). Fifteen minutes after adaptation to catheter placement, upstream and downstream responses to graded volumes of abrupt midesophageal infusions (graded stimuli, 0.1-5.0 ml, air, sterile water, and apple juice) were evaluated.…”

“…Manometry data analytical characteristics have been described before (11,15,16,21,30) and are briefly defined as follows. 1) Resting UES pressure was measured as an average of five UES pressure measurements at end expiration observed before stimulus or spontaneous swallow.…”