Lower esophageal sphincter relaxation reflex kinetics: effects of peristaltic reflexes and maturation in human premature neonates

Proton pump inhibitor therapy may alter the sensory motor characteristics of pharyngoesophageal motility in infants with suspected GERD

BACKGROUND

Acid reflux index (ARI) is a biomarker for gastroesophageal reflux disease (GERD). The effects of short-term proton pump inhibitor (PPI) therapy on pharyngoesophageal motility and clearance mechanisms in infants remain unknown. We hypothesized that pharyngoesophageal reflexes and response to PPI are distinct between infants with 3%-7% and >7% ARI.

METHODS

Secondary analysis was performed from a subset of infants who participated in a randomized controlled trial (NCT: 02486263). Infants (N = 36, 29.9 ± 4.3 weeks gestation) underwent 4 weeks of PPI therapy, 1 week of washout, and longitudinal testing to assess: (a) clinical outcomes; (b) pH-impedance and symptom metrics including ARI, distal baseline impedance, clearance time, refluxate height, symptoms, I-GERQ-R scores, symptom association probability; (c) pharyngoesophageal motility reflexes and sensory motor characteristics. Comparisons were performed between infants with 3%-7% versus >7% ARI.

KEY RESULTS

From the 36 hospitalized infants treated: Pharyngoesophageal reflex latencies were prolonged (p > 0.05) and duration in ARI 3%-7% group only (p = 0.01); GER frequency, proximal ascent and clearance increased (ARI 3%-7%); weight gain velocity, oral feeding success, and fine motor score decreased while length of hospital stays increased in the ARI >7% group despite the decrease in symptoms and I-GERQ-R scores.

CONCLUSIONS & INFERENCES

Distinct changes in pharyngoesophageal sensory motor aspects of motility and reflex mechanisms exist after using PPI therapy in infants. Contributory factors may include the effects of maturation and aerodigestive comorbidities (GERD and BPD). Controlled studies incorporating placebo are needed to delineate the effects of PPI on causal and adaptive GERD mechanisms in infants with aerodigestive and feeding-related comorbidities.

Diagnosis and Management of Pediatric Gastroesophageal Reflux in the Emergency Department

ABSTRACT

Gastroesophageal reflux (GER) is a common physiologic occurrence in infants, children, and adolescents and can develop into a pathological process (GERD) with associated complications. Gastroesophageal reflux is reported in approximately 30% of healthy infants, with a peak age of 3 to 4 months and is a common concern from families presenting to the emergency department. Evaluation and diagnosis of GER/GERD is primarily clinical and requires a detailed history, a complete physical examination, and exclusion of more severe extraesophageal pathologies. A high index of suspicion for GERD should be considered in patients with recurrent respiratory symptoms, difficulty with weight gain, and children with medically complex conditions who would be at higher risk for these complications. This review will briefly discuss diagnostic studies for the evaluation of GER/GERD; however, these are not helpful in the acute care setting and should be reserved for evaluation by a subspecialist. Management of GER/GERD includes nonmedication management with reflux precautions and dietary/lifestyle modifications; medication management with proton-pump inhibitors, H2 blockers, antacids, or prokinetics, as well as surgical management for refractory or high-risk cases.

Gastroesophageal reflux disease in children: What’s new right now?

Gastroesophageal reflux (GER) in children is very common and refers to the involuntary passage of gastric contents into the esophagus. This is often physiological and managed conservatively. In contrast, GER disease (GERD) is a less common pathologic process causing troublesome symptoms, which may need medical management. Apart from abnormal transient relaxations of the lower esophageal sphincter, other factors that play a role in the pathogenesis of GERD include defects in esophageal mucosal defense, impaired esophageal and gastric motility and clearance, as well as anatomical defects of the lower esophageal reflux barrier such as hiatal hernia. The clinical manifestations of GERD in young children are varied and nonspecific prompting the necessity for careful diagnostic evaluation. Management should be targeted to the underlying aetiopathogenesis and to limit complications of GERD. The following review focuses on up-to-date information regarding of the pathogenesis, diagnostic evaluation and management of GERD in children.

Pharyngeal biorhythms during oral milk challenge in high-risk infants: Do they predict chronic tube feeding?

BACKGROUND

Eating difficulties are common in high-risk neonatal intensive care unit (NICU) infants; mechanisms remain unclear. Crib-side pharyngo-esophageal motility testing is utilized to assess contiguous swallowing physiology, and cross-system interplay with cardio-respiratory rhythms. Aims were to: (1) identify whether distinct pharyngeal rhythms exist during oral milk challenge (OMC), and (2) develop a chronic tube feeding risk prediction model in high-risk infants.

METHODS

Symptomatic NICU infants (N = 56, 29.7 ± 3.7 weeks birth gestation) underwent pharyngo-esophageal manometry with OMC at 40.9 ± 2.5 weeks postmenstrual age (PMA). Exploratory cluster data analysis (partitioning around k-medoids) was performed to identify patient groups using pharyngeal contractile rhythm data (solitary swallows and swallows within bursts). Subsequently, (a) pharyngeal-esophageal, cardio-respiratory, and eating method characteristics were compared among patient groups using linear mixed models, and (b) chronic tube feeding prediction model was created using linear regression.

RESULTS

Three distinct patient groups were identified with validity score of 0.6, and termed sparse (high frequency of solitary swallows), intermediate, or robust (high swallow rate within bursts). Robust group infants had: lesser pharyngeal and esophageal variability, greater deglutition apnea, pharyngeal activity, and esophageal activity (all p < 0.05), but less frequent heart rate decreases (p < 0.05) with improved clinical outcomes (milk transfer rate, p < 0.001, and independent oral feeding at discharge, p < 0.03). Chronic tube feeding risk = -11.37 + (0.22 × PMA) + (-0.73 × bronchopulmonary dysplasia) + (1.46 × intermediate group) + (2.57 × sparse group).

CONCLUSIONS

Robust pharyngeal rhythm may be an ideal neurosensorimotor biomarker of independent oral feeding. Differential maturation of cranial nerve-mediated excitatory and inhibitory components involving foregut, airway, and cardiac rhythms distinguishes the physiologic and pathophysiologic basis of swallowing and cardio-respiratory adaptation.

Evidence-Based Approaches to Successful Oral Feeding in Infants with Feeding Difficulties

Infants in the neonatal intensive care unit (NICU) frequently have feeding difficulties with the root cause remaining elusive to identify. Evaluation of the provider/parent/infant feeding process may provide objective clues to sources of feeding difficulty. Specialized testing may be necessary to determine if the infant's swallowing skills are dysfunctional, immature, or maldeveloped, and to determine the risk of feeding failure or chronic tube feeding. Current evidence-based diagnostic and management approaches resulting in successful oral feeding in the NICU infant are discussed.

Impact of esophageal mucosal permeability markers on provocation-induced esophageal reflexes in high-risk infants

Esophageal distal baseline impedance (DBI) is an indicator of mucosal integrity; lower values suggest increased permeability. Aims were to characterize the (1) effect of DBI category (<900 Ω, 900-2000 Ω, and >2000 Ω) on sensory-motor characteristics of mid-esophageal provocation-induced motility reflexes, and (2) clinical outcomes among high-risk human infants evaluated for gastroesophageal reflux disease. Symptomatic infants (N = 49, 41 ± 3 weeks postmenstrual age) underwent pH-impedance testing to characterize acid reflux index (ARI) and DBI, and pharyngo-esophageal manometry to examine upper esophageal sphincter (UES), peristaltic, and lower esophageal sphincter (LES) functions. Sensory-motor response characteristics included response threshold (ml), occurrence (%), latency (s), duration (s), and magnitude (mmHg) upon mid-esophageal stimulations (0.1-2.0 ml of air, water, and apple juice). Motility and clinical outcomes were compared among DBI groups. In infants with DBI <900 Ω and 900-2000 Ω (vs. >2000 Ω): (a) Long-term feeding milestones did not differ (p > 0.05); (b) complete peristaltic propagation decreased in 900-2000 Ω (p < 0.05), polymorphic waveforms increased in <900 Ω and 900-2000 Ω (p < 0.05); (c) media effects were noted with liquids (vs. air) wherein UES and esophageal contractility were prolonged in <900 Ω and 900-2000 Ω (p < 0.05), and esophageal sensitivity heightened for <900 Ω with water and for 900-2000 Ω with air (both p < 0.05). ARI was not correlated with DBI in infants with chronic lung disease (r = 0.05, p = 0.82). We conclude that pharyngo-esophageal motility sensory-motor characteristics in infants are modified by DBI category. These preliminary findings pave-the-way for further physiological testing in convalescing high-risk infants to ascertain potential mechanisms of airway-digestive reflex interactions and symptom generation, which may lead to targeted therapies.

Review of paediatric gastrointestinal physiology relevant to the absorption of orally administered medicines

Despite much progress in regulations to improve paediatric drug development, there remains a significant need to develop better medications for children. For the design of oral dosage forms, a detailed understanding of the specific gastrointestinal (GI) conditions in children of different age categories and how they differ from GI conditions in adults is essential. Several review articles have been published addressing the ontogeny of GI characteristics, including luminal conditions in the GI tract of children. However, the data reported in most of these reviews are of limited quality because (1) information was cited from very old publications and sometimes low quality sources, (2) data gaps in the original data were filled with textbook knowledge, (3) data obtained on healthy and sick children were mixed, (4) average data obtained on groups of patients were mixed with data obtained on individual patients, and (5) results obtained using investigative techniques that may have altered the outcome of the respective studies were considered. Consequently, many of these reviews draw conclusions that may be incorrect. The aim of the present review was to provide a comprehensive and updated overview of the available original data on the ontogeny of GI luminal conditions relevant to oral drug absorption in the paediatric population. To this end, the PubMed and Web of Science metadatabases were searched for appropriate studies that examined age-related conditions in the oral cavity, esophagus, stomach, small intestine, and colon. Maturation was observed for several GI parameters, and corresponding data sets were identified for each paediatric age group. However, it also became clear that the ontogeny of several GI traits in the paediatric population is not yet known. The review article provides a robust and valuable data set for the development of paediatric in vitro and in silico biopharmaceutical tools to support the development of age-appropriate dosage forms. In addition, it provides important information on existing data gaps and should provide impetus for further systematic and well-designed in vivo studies on GI physiology in children of specific age groups in order to close existing knowledge gaps and to sustainably improve oral drug therapy in children.

Pathophysiology of Pediatric Gastroesophageal Reflux Disease: Similarities and Differences With Adults

Gastroesophageal reflux (GOR) is defined as "the passage of gastric contents into the esophagus with or without regurgitation and vomiting" and gastroesophageal reflux disease (GORD) is defined "when GOR leads to troublesome symptoms affecting the daily functioning and/or complications." This definition was first developed in 2006 by the Montreal consensus group (1) and later on adopted by pediatric gastroenterology societies such as ESPGHAN and NASPGHAN in 2009 (2). The definition of gastroesophageal reflux reveals little about its pathophysiology and is focused on symptomatology. In this way, it acts as an umbrella term for the multifactorial causes of the disease and the various phenotypes encountered; from functional heartburn to hypersensitive esophagus and nonerosive reflux disease, to erosive esophagitis and Barrett's esophagus. This article is devoted to the pathophysiology of pediatric GORD in comparison to adult GORD and is divided in 2 parts. In the first part, we will systematically describe the different mechanisms for the generation and clearance of reflux events, while on the second part we will discuss the mechanisms involved in symptoms generation. Finally, we will discuss the similarities and differences between pediatric and adult GORD.

Esophageal impedance baseline in infants with bronchopulmonary dysplasia: A pilot study

BACKGROUND

Bronchopulmonary dysplasia (BPD) may induce gastroesophageal reflux (GER). Esophageal impedance baseline values (BI) reflect mucosal inflammation. Our aim was to evaluate BI levels in preterm infants with BPD compared with those without BPD and to identify BI predictors.

METHODS

This is a retrospective pilot study including infants born <32 weeks' gestational age (GA) who underwent esophageal multichannel intraluminal impedance (MII)-pH. Univariate/multivariate analysis were performed to compare data between BPD and non-BPD infants and to identify BI predictors. A subgroup analysis was performed in infants born <29 weeks' GA, at highest risk for BPD.

RESULTS

Ninety-seven patients (median GA 28^5/7 weeks, mean postnatal age 49 days, 29 with BPD), were studied. BPD infants had significantly lower birth weight compared with non-BPD infants (750 vs. 1275 g), were more immature (27^4/7 vs. 29^0/7 weeks GA), were older at MII-pH (79 vs. 38 days) and received less fluids during MII-pH (147 vs. 161 ml/kg/day). The same findings were found in the group of 53 infants born <29 weeks. BPD versus non-BPD infants had significantly lower BI (2050 vs. 2574 ohm, p = 0.007) (<1000 ohm in five BPD infants vs. one non-BPD) whereas the other MII-pH parameters were not significantly different. Multiple regression analysis found that increasing chronological age was positively associated with BI (B = 9.3, p = 0.013) whereas BPD was associated with lower BI (B = -793.4, p < 0.001).

CONCLUSIONS

BPD versus non-BPD infants had significantly lower BI despite similar MII-pH data. BPD and chronological age predicted BI, whereas only BPD predicted BI in the most immature infants.

Pharyngoesophageal motility reflex mechanisms in the human neonate: importance of integrative cross-systems physiology

Swallowing is a critical function for survival and development in human neonates and requires cross-system coordination between neurological, airway, and digestive motility systems. Development of pharyngoesophageal motility is influenced by intra- and extrauterine development, pregnancy complications, and neonatal comorbidities. The primary role of these motility reflex mechanisms is to maintain aerodigestive homeostasis under basal and adaptive biological conditions including oral feeding, gastroesophageal reflux, and sleep. Failure may result in feeding difficulties, airway compromise, dysphagia, aspiration syndromes, and chronic eating difficulties requiring prolonged tube feeding. We review the integration of cross-systems physiology to describe the basis for physiological and pathophysiological neonatal aerodigestive functions.

Characterization of Esophageal and Sphincter Reflexes across Maturation in Dysphagic Infants with Oral Feeding Success vs Infants requiring Gastrostomy

To test the hypothesis that esophageal and sphincteric sensory-motor reflexes are distinct across maturation in infants with dysphagia receiving gastrostomy-tube (G-tube). This is a retrospective review of 29 dysphagic infants (N = 15 study requiring gastrostomy, N = 14 age matched control achieving oral feeds) that underwent longitudinal pharyngeal-esophageal manometry at 42.3 (37-50.2) weeks postmenstrual age (PMA) and 48.9 (43.3-57.9) weeks PMA. Graded stimuli (0.1-5 mL) of varying media (air, water, and apple juice) tested esophageal peristaltic reflex, upper esophageal sphincter contractile reflex (UESCR), and lower esophageal sphincter relaxation reflex (LESRR). Comparisons were performed between study and controls and across maturation (time-1 vs time-2). Data represented as mean ± SE or OR (95% CI). Across maturation (time-1 vs time-2): Study infants did not exhibit significant differences across in peristaltic, UES, or LES reflexes (all p > 0.05). In contrast, controls exhibited increased UES resting pressure (13 ± 3 vs 17 ± 3 mmHg, p = 0.001), LES resting pressure (22 ± 3 vs 25 ± 3 mmHg, p < 0.009), LES nadir pressure (0.5 ± 1 vs 4.3 ± 1 mmHg, p = 0.001), and esophago-deglutition responses [2.5 (1.23-4.88), p = 0.04], and decreased secondary peristalsis [0.44 (0.31-0.61), p = 0.001], UESCR [0.4 (0.25-0.65), p = 0.001], LESRR [0.4 (0.24-0.75), p = 0.01], and symptoms [0.6 (0.45-0.83), p = 0.005]. Among infants with dysphagia, esophageal provocation induced peristaltic reflex, UESCR, and LESRR advance with longitudinal maturation when infants are oral-fed successfully, but not in those who received gastrostomy. Underlying mechanisms may be related to esophageal sensitivity, afferent or efferent transmission, and coordination of upstream excitation and downstream inhibition, which can be potential therapeutic targets for improving feeding capabilities after gastrostomy placement in infants with dysphagia.

Differentiating esophageal sensitivity phenotypes using pH-impedance in intensive care unit infants referred for gastroesophageal reflux symptoms

BACKGROUND

To identify esophageal sensitivity phenotypes relative to acid (S_Acid), bolus (S_Bolus), acid and bolus (S_Acid+Bolus), and none (S_None) exposures in infants suspected with gastroesophageal reflux disease (GERD).

METHODS

Symptomatic infants (N = 279) were evaluated for GERD at 42 (40-45) weeks postmenstrual age using 24-h pH-impedance. Symptom-associated probability (SAP) for acid and bolus components defined esophageal sensitivity: (1) S_Acid as SAP ≥ 95% for acid (pH < 4), (2) S_Bolus as SAP ≥ 95% for bolus, (3) S_Acid+Bolus as SAP ≥ 95% for acid and bolus, or (4) S_None as SAP < 95% for acid and bolus.

RESULTS

Esophageal sensitivity prevalence (S_Acid, S_Bolus, S_Acid+Bolus, S_None) was 28 (10%), 94 (34%), 65 (23%), and 92 (33%), respectively. Emesis occurred more in S_Bolus and S_Acid+Bolus vs S_None (p < 0.05). Magnitude (#/day) of cough and emesis events increased with S_Bolus and S_Acid+Bolus vs S_None (p < 0.05). S_Acid+Bolus had increased acid exposure vs S_None (p < 0.05). Distributions of feeding and breathing methods were distinct in infants with S_Bolus vs S_None (both, p < 0.05). Multivariate analysis revealed that arching and irritability events/day were lesser at higher PMAs (p < 0.001) and greater for infants on NCPAP (p < 0.01) with S_Bolus and S_Acid+Bolus (p < 0.05). Coughs/day was greater at higher PMAs (p < 0.001) for infants with gavage and transitional feeding methods (p < 0.02) with S_Bolus and S_Acid+Bolus (p < 0.05) but lesser with Trach (p < 0.001). Number of emesis events/day were greater with S_Bolus and S_Acid+Bolus (p < 0.001). Sneezes/day decreased for infants on Trach (p = 0.02).

CONCLUSIONS

Feeding and breathing methods can influence the frequency and type of aerodigestive symptoms. We differentiated esophageal sensitivity phenotypes in NICU infants referred for GERD symptoms using pH-impedance. Acid sensitivity alone was rare, which may explain poor response to acid suppressives; aerodigestive symptoms were predominantly linked with bolus spread. Magnitude of esophageal acid exposure and esophageal sensitivity to bolus spread may explain the pathophysiological basis for symptoms.

IMPACT

Objective GERD diagnosis and reasons for symptoms in NICU infants remains unclear. Differentiation of esophageal sensitivities by acid and bolus components of GER reveal distinct symptom profiles, specifically the bolus component of GER significantly contributes to symptom occurrence. Acid only sensitivity to GER is rare, and acid-suppressive therapy alone may not improve symptoms in a majority of NICU infants. Magnitude of esophageal acid exposure and esophageal sensitivity to any bolus spread may explain the pathophysiological basis for symptoms. Feeding and breathing methods can influence the frequency and type of aerodigestive symptoms. GERD treatments should be individualized to the patient's GERD phenotype and likely also target the bolus component of GER.

Response to therapy among neonates with gastro-esophageal reflux is associated with esophageal clearance

BACKGROUND

Few studies evaluated the efficacy of pharmacological therapy for gastro-esophageal reflux disease (GERD) in newborns, whose safety has been questioned. Esophageal basal impedance (BI) is a marker of mucosal integrity, and treatment with proton pump inhibitors significantly increases BI in infants; however, no correlation with clinical improvement was reported.

AIMS

To evaluate the relationship between BI and other esophageal pH-impedance parameters and clinical response to therapy in newborns with GERD.

STUDY DESIGN

Multicenter retrospective study.

SUBJECTS

Infants who received omeprazole or ranitidine for GERD.

OUTCOME MEASURES

Complete response to therapy was defined as symptom decrease by ≥50% compared to baseline, partial response as symptom decrease <50%, no response as no symptom decrease based on chart analysis. Response to therapy was assessed 2 and 4 weeks after the onset of therapy. Univariate and multivariate statistics were performed to assess associations between response to therapy and clinical/pH-impedance parameters.

RESULTS

We studied 60 infants (51 born preterm): 47 received omeprazole, 13 ranitidine. Response to therapy was associated with decreasing esophageal clearance time: odds ratio 0.308, 95%CI 0.126-0.753, p = 0.010 at 2 weeks, odds ratio 0.461, 95%CI 0.223-0.955, p = 0.037 at 4 weeks.

CONCLUSIONS

Clinical response to therapy among infants with GERD was associated with esophageal clearance but not with esophageal BI level.

Impact of Feeding Strategies With Acid Suppression on Esophageal Reflexes in Human Neonates With Gastroesophageal Reflux Disease: A Single-Blinded Randomized Clinical Trial

INTRODUCTION

Aims were to test hypothesis that esophageal provocation-induced reflexes are superior with acid suppression plus feeding modifications vs acid suppression alone among infants treated for gastroesophageal reflux disease (GERD).

METHODS

Infants (N = 49, 41.3 ± 2.6 of postmenstrual age) with acid reflux index >3% underwent longitudinal motility testing (weeks 0 and 5) with graded midesophageal provocation to test randomly allocated therapies (4 weeks' proton pump inhibitor [PPI] ± feeding modifications) on sensory-motor aerodigestive reflexes. Feeding modification included restricted fluid volume <140 mL/kg per day, fed over 30 minutes in right lateral position and supine postprandial position. Primary motility outcome was frequency-occurrence of peristaltic reflex. Secondary outcomes included upper esophageal sphincter contractile reflex, lower esophageal sphincter (LES) relaxation reflex, respiratory change, and symptom characteristics.

RESULTS

Treatment groups did not differ for primary outcome (odds ratio = 0.8, 95% confidence interval 0.4-1.6, P = 0.99) or secondary outcomes (all P > 0.05). For both treatment groups at follow-up, distal esophageal contraction and LES tone decreased, and LES relaxation reflex occurrence is less frequent (all P < 0.05). In a subgroup analysis, comparing infants with PPI washout (N = 40) vs with continued (N = 9) PPI therapy, no differences were noted for aerodigestive reflex response frequency-occurrence (all P > 0.05).

DISCUSSION

In infants with GERD, feeding modification with acid suppression is not superior to acid suppression alone in modifying aerodigestive reflexes (frequency, sensation, or magnitude). Contiguous areas targeted by GER, i.e., LES and distal esophageal functions, worsened at follow-up for both groups despite PPI therapy. Maturation is likely the key factor for GERD resolution in infants, justifying the use of placebo in clinical trials for objectively determined GERD.

Mechanisms of bradycardia in premature infants: Aerodigestive-cardiac regulatory-rhythm interactions

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.

Gastroesophageal Reflux Disease in the Neonatal Intensive Care Unit Neonate: Controversies, Current Understanding, and Future Directions

Gastroesophageal reflux (GER) is considered physiologic and is a normal process; whereas, when aerodigestive consequences are associated, it is often interpreted as GER disease (GERD). However, the distinction between them remains a challenge in infants in the NICU. Reflux-type of symptoms are heterogeneous, and often managed with changes in diet, feeding methods, and acid-suppressive therapy; all these empiric therapies lack objectivity; hence, practice variation is universal. We clarify the current controversies, explain the potential role of GERD in causing symptoms and complications, and highlight current advances. The evidence basis for the diagnostic strategies is discussed.

Maturation of Esophageal Motility and Esophagogastric Junction in Preterm Infants

BACKGROUND

Preterm infants commonly present with oral feeding problems. The role of maturation of esophageal bolus transport mechanisms herein remains unclear.

OBJECTIVES

To characterize esophageal motility and function of esophagogastric junction (EGJ) during deglutitive swallowing in healthy preterm infants and to describe maturational changes.

METHODS

Four consecutive high-resolution manometry studies with impedance studies were performed weekly to investigate esophageal motility and EGJ function. Esophageal pressure topography and pressure-impedance metrics were derived. Mixed models with repeated measures were used for statistical analysis.

RESULTS

We analyzed 137 nutritive swallows from 36 motility studies in 10 preterm infants. The mean gestational age was 30.17 ± 0.94 weeks; the mean postmenstrual age at time point 1 and 4 was 34.42 ± 0.86 and 37.45 ± 1.16 weeks, respectively. Esophageal peristaltic wave patterns in response to nutritive swallows were observed in all patients. At later time points, esophageal body peristalsis became more rapid, evidenced by a faster distal contractile velocity and shorter distal latency (p = 0.002 and p < 0.0001, respectively). In addition, 4-s integrated relaxation pressures increased and distal contractile integral decreased at later time points (p = 0.003 and p = 0.021, respectively). Bolus clearance also improved at later age (p = 0.008).

CONCLUSIONS

Preterm infants demonstrate peristaltic esophageal motility following nutritive swallows. However, alterations in esophageal bolus transport in relation to peristalsis are demonstrated. Peristaltic progression becomes more rapid, while deglutitive relaxation pressures increase with increasing age. These maturational changes may suggest further development of the enteric nervous system after birth in former preterm neonates.

Persistent feeding difficulties among infants with fetal opioid exposure: mechanisms and clinical reasoning

Aims: Infants with fetal exposure to opioids have varying pattern of feeding difficulties mainly manifesting as difficulties with aerodigestive adaptation and disruptive feeding behavior. The reasons are unclear; in a pilot study, we determined basal and adaptive pharyngo-esophageal motility in a group of infants with fetal exposure to opioids and persistent feeding difficulties impeding their discharge. Methods: Six infants with fetal opioid exposure compared to 12 controls who underwent basal and adaptive pharyngo-esophageal manometry to characterize the basis for their symptoms. Spontaneous swallows (N = 180) and pharyngeal stimuli (N = 113)-induced swallowing responses were analyzed. Results: Resting upper esophageal sphincter (UES) pressure was similar in both the groups, but resting lower esophageal sphincter (LES) pressure was significantly high and it relaxed slowly and inadequately in opioid-exposed infants (p < .05). Upon pharyngeal provocation, opioid-exposed infants had higher LES nadir pressure, increased duration of esophageal body contraction at proximal-, mid-, and distal-esophagus, as well as greater area under the curve with distal esophageal waveforms, compared to controls (all p < .05). Conclusions: These pilot observations are suggestive of up-regulation of central vagal effects with heightened cholinergic excitatory responses and inadequate relaxation responses at the foregut, and may form the basis for persistent feeding difficulties in opioid-exposed infants. Abnormality with both sensory and motor aspects of vagal reflexes may be contributory.

Gastroesophageal Reflux Disease in the Neonatal Intensive Care Unit Infant: Who Needs to Be Treated and What Approach Is Beneficial?

Gastroesophageal reflux (GER) and GER disease (GERD) pertaining to infants in the neonatal intensive care unit (NICU) are reviewed, based on research in this specific population. The developmental biology of the gastroesophageal junction, physiology of GER, and pathophysiology of GERD in this setting are summarized, and risk factors for GER and GERD identified. The epidemiology, economic burden, and controversies surrounding GERD in NICU infants are addressed, and an approach to GER and GERD in these patients formulated. Recent advancements in individual assessment of GER and GERD in the NICU infant are examined, and evidence-based guidelines for their adoption provided.

Mechanisms of Aerodigestive Symptoms in Infants with Varying Acid Reflux Index Determined by Esophageal Manometry

OBJECTIVE

To test whether symptom generation in infants is related to the severity of gastroesophageal reflux disease (GERD) symptoms as determined by the Acid Reflux Index (ARI), stimulus media, and stimulus volume during provocative esophageal manometry.

STUDY DESIGN

Symptomatic neonates (n = 74) born at a median of 28.9 weeks gestation (range, 23.4-39.4 weeks) were studied at a median of 41.0 weeks (range, 34.6-48.0 weeks) postmenstrual age using 24-hour pH-impedance methods to determine ARI severity, followed by provocative esophageal manometry with graded mid-esophageal infusions (0.1-5.0 mL) of air, water, and apple juice. Peristaltic reflexes and symptom characteristics were compared among ARI severity categories using linear mixed models and generalized estimating equations.

RESULTS

The effects of 2635 separate esophageal stimuli on reflexes and symptoms were analyzed. Peristaltic reflexes occurred in 1880 infusions (71%), and physical, cardiorespiratory, sensory symptoms were seen in 439 infusions (17%). Symptom prevalence did not differ across the ARI severity categories (ARI <3, 18%; ARI 3-7, 17%; ARI >7, 16%; P = 1.0). Symptom and peristaltic responses increased with incremental stimulus volumes (all media, P < .001).

CONCLUSIONS

Symptoms and peristaltic reflexes are manifestations of the recruitment of several neurosensory and neuromotor pathways evoked by mid-esophageal infusions. ARI severity grade plays no role in symptom generation, indicating that GERD should not be diagnosed and severity should not be assigned based on symptoms alone. An increase in symptom occurrence was noted with increasing stimulus volumes, which provided increased activation of receptors, afferents, and efferents in evoking peristaltic clearance reflexes.

Gastro-oesophageal reflux: a mixed methods study of infants admitted to hospital in the first 12 months following birth in NSW (2000-2011)

BACKGROUND

Gastro-oesophageal reflux (GOR) is common in infants. When the condition causes pathological symptoms and/or complications it is considered gastro-oesophageal reflux disease (GORD). It appears to be increasingly diagnosed and causes great distress in the first year of infancy. In New South Wales (NSW), residential parenting services support families with early parenting difficulties. These services report a large number of babies admitted with a label of GOR/GORD. The aim of this study was to explore the maternal and infant characteristics, obstetric interventions, and reasons for clinical reporting of GOR/GORD in NSW in the first 12 months following birth (2000-2011).

METHODS

A three phase, mixed method sequential design was used. Phase 1 included a linked data population based study (n = 869,188 admitted babies). Phase 2 included a random audit of 326 medical records from admissions to residential parenting centres in NSW (2013). Phase 3 included eight focus groups undertaken with 45 nurses and doctors working in residential parenting centres in NSW.

RESULTS

There were a total of 1,156,020 admissions recorded of babies in the first year following birth, with 11,513 containing a diagnostic code for GOR/GORD (1% of infants admitted to hospitals in the first 12 months following birth). Babies with GOR/GORD were also more likely to be admitted with other disorders such as feeding difficulties, sleep problems, and excessive crying. The mothers of babies admitted with a diagnostic code of GOR/GORD were more likely to be primiparous, Australian born, give birth in a private hospital and have: a psychiatric condition; a preterm or early term infant (37-or-38 weeks); a caesarean section; an admission of the baby to SCN/NICU; and a male infant. Thirty six percent of infants admitted to residential parenting centres in NSW had been given a diagnosis of GOR/GORD. Focus group data revealed two themes: "It is over diagnosed" and "A medical label is a quick fix, but what else could be going on?"

CONCLUSIONS

Mothers with a mental health disorder are nearly five times as likely to have a baby admitted with GOR/GORD in the first year after birth. We propose a new way of approaching the GOR/GORD issue that considers the impact of early birth (immaturity), disturbance of the microbiome (caesarean section) and mental health (maternal anxiety in particular).

Effects of Esophageal Acidification on Troublesome Symptoms: An Approach to Characterize True Acid GERD in Dysphagic Neonates

To quantify and compare maximal extent (height) of acid reflux events (AREs) on symptom generation in dysphagic neonates. Dysphagic neonates (N = 53), born at 30 ± 5.3 weeks gestation, underwent 24-hour pH-impedance study for the evaluation of troublesome symptoms purported to be due to gastroesophageal reflux disease (GERD). AREs (pH < 4 for >4 s) detected by impedance (Z) were categorized by maximal extent as refluxate reaching distal (Z6, Z5), middle (Z4, Z3), or proximal (Z2, Z1) impedance channels. AREs reaching the pH sensor only were categorized as distal. Symptom correlation (%, symptom index, symptom sensitivity index, and symptom associated probability) and temporal characteristics (clearance times) of AREs were analyzed using linear mixed and GEE models comparing height categories presented as mean ± SEM, median (IQR), and OR (95% CI). Of the 2003 AREs, 1) distal extent AREs (n = 1642) had increased frequency (p < 0.05), decreased ACT (p < 0.05), and decreased acidity (p < 0.05); 2) in middle and proximal AREs, acid clearance was longer than bolus clearance, (p < 0.01); and 3) the odds of having cardiorespiratory (cough or sneeze) symptoms are increased with proximal and middle AREs (p < 0.05). Most proximal ascent of AREs into middle or proximal esophagus likely activates protective aerodigestive reflexes (peristalsis) or vigilant states to facilitate bolus and chemical clearance. Heightened esophageal sensitivity, acid neutralization delays, or clearance mechanism delays may accentuate multi-systemic troublesome symptoms.

Advances with Neonatal Aerodigestive Science in the Pursuit of Safe Swallowing in Infants: Invited Review

Feeding, swallowing, and airway protection are three distinct entities. Feeding involves a process of sequential, neurosensory, and neuromotor interactions of reflexes and behaviors facilitating ingestion. Swallowing involves anterograde bolus movement during oral-, pharyngeal-, and esophageal phases of peristalsis into stomach. During these events, coordination with airway protection is vital for homeostasis in clearing any material away from airway vicinity. Neurological-airway-digestive inter-relationships are critical to the continuum of successful feeding patterns during infancy, either in health or disease. Neonatal feeding difficulties encompass a heterogeneous group of neurological, pulmonary, and aerodigestive disorders that present with multiple signs posing as clinical conundrums. Significant research breakthroughs permitted understanding of vagal neural pathways and functional aerodigestive connectivity involved in regulating swallowing and aerodigestive functions either directly or indirectly by influencing the supra-nuclear regulatory centers and peripheral effector organs. These neurosensory and neuromotor pathways are influenced by pathologies during perinatal events, prematurity, inflammatory states, and coexisting medical and surgical conditions. Approaches to clarify pathophysiologic mapping of aerodigestive interactions, as well as translating these discoveries into the development of personalized and simplified feeding strategies to advance child health are discussed in this review article.

Effect of nasal noninvasive respiratory support methods on pharyngeal provocation-induced aerodigestive reflexes in infants

The pharynx is a locus of provocation among infants with aerodigestive morbidities manifesting as dysphagia, life-threatening events, aspiration-pneumonia, atelectasis, and reflux, and such infants often receive nasal respiratory support. We determined the impact of different oxygen delivery methods on pharyngeal stimulation-induced aerodigestive reflexes [room air (RA), nasal cannula (NC), and nasal continuous positive airway pressure (nCPAP)] while hypothesizing that the sensory motor characteristics of putative reflexes are distinct. Thirty eight infants (28.0 ± 0.7 wk gestation) underwent pharyngoesophageal manometry and respiratory inductance plethysmography to determine the effects of graded pharyngeal stimuli (n = 271) on upper and lower esophageal sphincters (UES, LES), swallowing, and deglutition-apnea. Comparisons were made between NC (n = 19), nCPAP (n = 9), and RA (n = 10) groups. Importantly, NC or nCPAP (vs. RA) had: 1) delayed feeding milestones (P < 0.05), 2) increased pharyngeal waveform recruitment and duration, greater UES nadir pressure, decreased esophageal contraction duration, decreased distal esophageal contraction amplitude, and decreased completely propagated esophageal peristalsis (all P < 0.05), and 3) similarly developed UES contractile and LES relaxation reflexes (P > 0.05). We conclude that aerodigestive reflexes were similarly developed in infants using noninvasive respiratory support with adequate upper and lower aerodigestive protection. Increased concern for GERD is unfounded in this population. These infants may benefit from targeted oromotor feeding therapies and safe pharyngeal bolus transit to accelerate feeding milestones.

Effects of pacifier and taste on swallowing, esophageal motility, transit, and respiratory rhythm in human neonates

BACKGROUND

Pacifier use is widely prevalent globally despite hygienic concerns and uncertain mechanistic effects on swallowing or airway safety.

AIMS

The effects of pacifier and taste interventions on pharyngo-esophageal motility, bolus transit, and respiratory rhythms were investigated by determining the upper esophageal sphincter (UES), esophageal body, esophagogastric junction (EGJ) motor patterns and deglutition apnea, respiratory rhythm disturbances, and esophageal bolus clearance.

METHODS

Fifteen infants (six males; median gestation 31 weeks and birth weight 1.4 kg) underwent high-resolution impedance manometry at 43 (41-44) weeks postmenstrual age. Manometric, respiratory, and impedance characteristics of spontaneous swallows, pacifier-associated dry swallowing and taste (pacifier dipped in 3% sucrose)-associated swallowing were analyzed. Linear mixed and generalized estimating equation models were used. Data are presented as mean ± SEM, %, or median (IQR).

KEY RESULTS

Pharyngo-esophageal motility, respiratory, and impedance characteristics of 209 swallows were analyzed (85 spontaneous swallows, 63 pacifier- swallows, 61 taste- swallows). Basal UES and EGJ pressures decreased upon pacifier (p < 0.05) and taste interventions (p < 0.05); however, esophageal motility, respiratory rhythm, and impedance transit characteristics were similar with both interventions.

CONCLUSIONS & INFERENCES

Oral stimulus with pacifier or taste interventions decreases UES and EGJ basal pressure, but has no effects on pharyngo-esophageal motility, airway interactions, or esophageal bolus transit. A decrease in central parasympathetic-cholinergic excitatory drive is likely responsible for the basal effects.

Dysphagia in the high-risk infant: potential factors and mechanisms

Neonatal dysphagia, or abnormalities of swallowing, represent a major global problem, and consequences of dysfunctional feeding patterns carry over into infancy and toddler age groups. Growth, development, and independent feeding skills are all delayed among high-risk infants. Such a group comprises premature birth, low-birth-weight, congenital anomalies, perinatal asphyxia, postsurgical, and sepsis categories. The conflict between pathophysiologic and pragmatic feeding strategies remains a major conundrum and is largely due to a lack of validated diagnostic approaches amid heterogeneity of the patient phenotype. Thus, well-tested feeding management strategies that can be generalizable are lacking. Furthermore, the aerodigestive symptoms and signs, potential risk factors, and contributory etiologies remain nonspecific. This article presents mechanistic evidence related to the pathophysiologic basis of neonatal dysphagia as well as potential opportunities to improve feeding abilities and long-term development.

Gestational and postnatal modulation of esophageal sphincter reflexes in human premature neonates

BACKGROUND

Effects of gestational age (GA) and postnatal maturation on upper and lower esophageal sphincter (UES and LES) reflex development remain unclear. We hypothesized very-preterm (VPT) born neonates (< 32 wk GA) have delayed maturation of UES contractile reflex (UESCR) and LES relaxation reflex (LESRR) vs. preterm (PT) born (32-37 wk GA) neonates.

METHODS

Using provocative manometry, effects of 1,263 graded mid-esophageal stimuli (air, liquid) on sensory-motor characteristics of UESCR and LESRR were investigated in 24 VPT-born and 12 PT-born neonates (37.8 ± 0.6 vs. 38.9 ± 0.4 wk postmenstrual age respectively, P = 0.14).

RESULTS

In response to liquid stimuli (vs. air), VPT-born neonates displayed prolonged UESCR and LESRR response latencies (P < 0.001) and prolonged UESCR and LESRR durations (P < 0.01); unlike PT-born neonates, who exhibit prolonged LESRR response latency (P < 0.01), but similar UESCR and LESRR durations (P = 0.2). Differences were noted in LESRR duration in VPT vs. PT neonates for air stimuli (P = 0.04). With liquid stimuli, increasing GA was associated with decreasing response onset latencies to UESCR and LESRR (P < 0.05), and increasing LESRR duration (P = 0.02).

CONCLUSION

Using GA as categorical or continuous variable, vagus-mediated mechano-sensitive and liquid-sensitive reflex characteristics of UESCR and LESRR are distinct; LESRR differs with varying intrauterine maturation suggesting inhibitory modulation progresses with advancing maturation.

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.

Mechanisms of cough provocation and cough resolution in neonates with bronchopulmonary dysplasia

BACKGROUND

Cough and deglutition are protective mechanisms that defend against aspiration. We identified mechanisms associated with cough provocation as well as those associated with cough resolution in infants with bronchopulmonary dysplasia (BPD).

METHODS

Manometry signatures of cough were recognized in 16 premature infants with BPD undergoing concurrent esophageal manometry, respiratory inductance plethysmography, and nasal air flow measurements. Pretussive and post-tussive pharyngo-esophageal motility changes were analyzed. Mechanisms associated with cough and mechanisms that restored respiratory and esophageal normalcy were analyzed.

RESULTS

We analyzed 312 cough events during 88 cough clusters; 97% were associated with recognizable manometric patterns. Initial mechanisms related with coughing included nonpropagating swallow (59%), upper esophageal sphincter (UES) reflex contraction (18%), and lower esophageal sphincter (LES) relaxation (14%). UES and LES dysfunction was present in 69% of nonpropagating swallow-associated cough clusters. Mechanisms restoring post-tussive normalcy included primary peristalsis (84%), secondary peristalsis (8%), and none recognized (8%). UES contraction reflex was associated with cough clusters more frequently in infants on nasal continuous positive airway pressure (NCPAP) (OR = 9.13, 95% CI = 1.88-44.24).

CONCLUSION

Cough clusters in infants with BPD had identifiable etiologies associated with esophageal events; common initial mechanisms were of upper aerodigestive origin, while common clearing mechanisms were peristaltic reflexes.

Development of Suck and Swallow Mechanisms in Infants

Preterm infants' hospital discharge is often delayed due to their inability to feed by mouth safely and competently. No evidence-based supported guidelines are currently available for health-care professionals caring for these infants. Available interventions advocating benefits are not readily acknowledged for lack of rigorous documentation inasmuch as any improvements may ensue from infants' normal maturation. Through research, a growing understanding of the development of nutritive sucking skills has emerged, shedding light on how and why infants may encounter oral feeding difficulties due to the immaturity of specific physiologic functions. Unfortunately, this knowledge has yet to be translated to the clinical practice to improve the diagnoses of oral feeding problems through the development of relevant assessment tools and to enhance infants' oral feeding skills through the development of efficacious preventive and therapeutic interventions. This review focuses on the maturation of the various physiologic functions implicated in the transport of a bolus from the oral cavity to the stomach. Although infants' readiness for oral feeding is deemed attained when suck, swallow, and respiration are coordinated, we do not have a clear definition of what coordination implies. We have learned that each of these functions encompasses a number of elements that mature at different times and rates. Consequently, it would appear that the proper functioning of sucking, the swallow processing, and respiration need to occur at two levels: first, the elements within each function must reach an appropriate functional maturation that can work in synchrony with each other to generate an appropriate suck, swallow process, and respiration; and second, the elements of all these distinct functions, in turn, must be able to do the same at an integrative level to ensure the safe and efficient transport of a bolus from the mouth to the stomach.

Upper and lower esophageal sphincter kinetics are modified during maturation: effect of pharyngeal stimulus in premature infants

BACKGROUND

We hypothesized that changes in proximal and distal esophageal sphincter kinetics evoked upon pharyngeal provocation undergo longitudinal maturation.

METHODS

Pharyngeal stimulation-induced reflexes were characterized using novel pharyngo-esophageal motility methods in 19 healthy premature neonates, studied at 34.7 ± 0.8 wk (time-1) and 39.3 ± 1.1 wk postmenstrual age (time-2). Graded volumes of air (290 infusions) and sterile water (172 infusions) were infused to define sensory-motor characteristics of upstream (pharyngeal reflexive swallow, PRS) and downstream (pharyngo-lower esophageal sphincter relaxation reflex, PLESRR) esophageal reflexes. Data displayed as mean ± SE.

RESULTS

Threshold volumes were similar with air and water for PRS and PLESRR at time-1 and time-2. Multiple PRS responses were noted with water stimulus and were different between the media (time-1 vs. air, P < 0.0001; time-2 vs. air, P = 0.0003). Dose-response relationships for water were significant (P < 0.01 for PRS and PLESRR time-1 and time-2), but not with air.

CONCLUSION

Significantly, the recruitment frequency of PRS and PLESRR increases with maturation, liquid is a superior medium for evoking such swallowing reflexes, and stimulus-response relationships for these reflexes are evident. These changes in aerodigestive protective reflexive activity may indicate differences in modulation of excitatory and inhibitory pathways during longitudinal postnatal maturation.

Upper gastrointestinal motility: prenatal development and problems in infancy

Deglutition, or swallowing, refers to the process of propulsion of a food bolus from the mouth into the stomach and involves the highly coordinated interplay of swallowing and breathing. At 34 weeks gestational age most neonates are capable of successful oral feeding if born at this time; however, the maturation of respiration is still in progress at this stage. Infants can experience congenital and developmental pharyngeal and/or gastrointestinal motility disorders, which might manifest clinically as gastro-oesophageal reflux (GER) symptoms, feeding difficulties and/or refusal, choking episodes and airway changes secondary to micro or overt aspiration. These problems might lead to impaired nutritional intake and failure to thrive. These gastrointestinal motility disorders are mostly classified according to the phase of swallowing in which they occur, that is, the oral preparatory, oral, pharyngeal and oesophageal phases. GER is a common phenomenon in infancy and is referred to as GERD when it causes troublesome complications. GER is predominantly caused by transient relaxation of the lower oesophageal sphincter. In oesophageal atresia, oesophageal motility disorders develop in almost all patients after surgery; however, a congenital origin of disordered motility has also been proposed. This Review highlights the prenatal development of upper gastrointestinal motility and describes the most common motility disorders that occur in early infancy.

Neuromotor mechanisms of pharyngoesophageal motility in dysphagic infants with congenital heart disease

BACKGROUND

Aero-digestive morbidities are common in congenital heart disease infants, and the mechanisms are unclear. We hypothesized that adaptive pharyngoesophageal motility reflexes are different in surgical congenital heart disease infants (S-CHD) vs. nonsurgical congenital heart disease infants (CHD) and healthy controls.

METHODS

Abrupt pharyngeal provocation was performed with graded water infusions using purpose-built micromanometry. The data from 12 S-CHD were compared with data from 10 CHD and 12 controls. One hundred and ninety-seven water stimulations were examined for the frequency, latency, duration, and magnitude of pharyngo-upper esophageal sphincter contractile response (PUCR), pharyngeal reflexive swallow (PRS), esophageal body peristalsis, and lower esophageal sphincter (LES) relaxation characteristics. Mixed statistical models were applied.

RESULTS

Frequency distribution (%) of PUCR: PRS: none in S-CHD vs. CHD vs. controls, respectively, were 36:46:17 vs. 9:80:11 vs. 15:61:24 (P < 0.05). Response latency to the final esophageal body waveform (P = 0.01) and the response duration of esophageal body peristalsis (P = 0.04) were prolonged in S-CHD vs. controls but were similar to CHD (P = 0.22). Pharyngeal infusion-induced LES relaxation characteristics were similar in all three groups.

CONCLUSION

Abnormality in the recruitment of PUCR or PRS reflexes and esophageal body peristalsis in S-CHD implicate dysregulation in vagal cholinergic excitatory neuromotor responses.

Esophageal reflexes modulate frontoparietal response in neonates: Novel application of concurrent NIRS and provocative esophageal manometry

Central and peripheral neural regulation of swallowing and aerodigestive reflexes is unclear in human neonates. Functional near infrared spectroscopy (NIRS) is a noninvasive method to measure changes in oxyhemoglobin (HbO) and deoxyhemoglobin (HbD). Pharyngoesophageal manometry permits evaluation of aerodigestive reflexes. Modalities were combined to investigate feasibility and to test neonatal frontoparietal cortical changes during pharyngoesophageal (visceral) stimulation and/or swallowing. Ten neonates (45.6 ± 3.0 wk postmenstrual age, 4.1 ± 0.5 kg) underwent novel pharyngoesophageal manometry concurrent with NIRS. To examine esophagus-brain interactions, we analyzed cortical hemodynamic response (HDR) latency and durations during aerodigestive provocation and esophageal reflexes. Data are presented as means ± SE or percent. HDR rates were 8.84 times more likely with basal spontaneous deglutition compared with sham stimuli (P = 0.004). Of 182 visceral stimuli, 95% were analyzable for esophageal responses, 38% for HDR, and 36% for both. Of analyzable HDR (n = 70): 1) HbO concentration (μmol/l) baseline 1.5 ± 0.7 vs. 3.7 ± 0.7 poststimulus was significant (P = 0.02), 2) HbD concentration (μmol/l) between baseline 0.1 ± 0.4 vs. poststimulus -0.5 ± 0.4 was not significant (P = 0.73), and 3) hemispheric lateralization was 21% left only, 29% right only, and 50% bilateral. During concurrent esophageal and NIRS responses (n = 66): 1) peristaltic reflexes were present in 74% and HDR in 61% and 2) HDR was 4.75 times more likely with deglutition reflex vs. secondary peristaltic reflex (P = 0.016). Concurrent NIRS with visceral stimulation is feasible in neonates, and frontoparietal cortical activation is recognized. Deglutition contrasting with secondary peristalsis is related to cortical activation, thus implicating higher hierarchical aerodigestive protective functional neural networks.

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

We tested the hypothesis that the sensory-motor characteristics of aerodigestive reflexes are dependent on stimulus type and volumes, sleep or awake states, and maturation. Thirteen neonates were studied at 33.6 ± 0.5 wk (time 1) and 37.3 ± 0.5 wk (time 2) postmenstrual age using multimodal provocative esophageal manometry concurrent with video polysomnography. Effects of graded volumes (399 infusions at time 1, 430 infusions at time 2) of midesophageal stimulation with air, water, and apple juice on the sensory thresholds and recruitment frequency of upper esophageal sphincter (UES), esophageal body, and lower esophageal sphincter (LES) reflexes were investigated during sleep and awake states. Sensory thresholds for aerodigestive reflexes between maturational stages were similar. Increased frequency recruitment of UES contractile reflex, LES relaxation reflex, and peristaltic reflexes were noted at time 2 (all, P < 0.05). Graded stimulus-response relationships were evident at time 1 and time 2 during awake and sleep states (P < 0.05). Secondary peristalsis vs. esophago-deglutition response proportions during sleep at time 1 vs. time 2 (P = 0.001) and awake vs. sleep at time 2 (P = 0.02) were distinct. We concluded that sensory-motor effects of esophageal mechanosensitivity, osmosensitivity, and chemosensitivity are advanced in sleep with maturation. Sleep further modulates the frequency recruitment and the type of aerodigestive reflexes.

Esophageal mechanosensitive mechanisms are impaired in neonates with hypoxic-ischemic encephalopathy

OBJECTIVES

To test the hypothesis that esophageal mechanodistention in infants with hypoxic-ischemic encephalopathy (HIE) results in altered upper esophageal sphincter (UES), esophageal body, and lower esophageal sphincter (LES) responses, compared with controls. As a secondary aim, we tested the hypothesis that infants with HIE receiving therapeutic hypothermia had different aerodigestive reflex characteristics than infants with HIE who received traditional neonatal care.

STUDY DESIGN

Provocative esophageal manometry was performed in 34 neonates (27 with HIE and 7 controls). Mechanodistention was performed using graded volumes of air. Peristaltic reflexes, UES contractile reflexes, and LES relaxation reflexes were analyzed for frequency, magnitude, and aberrancies.

RESULTS

Infants with HIE demonstrated more rapid recruitment of responses and greater UES magnitude (P < .05). They had more frequent secondary peristalsis and lower LES nadir pressures with prolonged LES nadir durations (P < .05). Most notable were the prolonged peristaltic response durations and increases in the number of polymorphic waveforms (P < .05). Compared with infants with HIE receiving traditional care, infants with HIE treated with hypothermia had higher UES pressures and shorter peristaltic response duration (P < .05).

CONCLUSIONS

Mechanodistention in infants with HIE results in upregulation of central vagal effects (ie, heightened cholinergic excitatory responses as demonstrated by exaggerated UES contractile reflex activity and heightened inhibitory responses evident by exaggerated LES relaxation reflex activity). Prolonged and poorly coordinated peristaltic responses may underlie dysfunction of aerodigestive regulation. Modulation of sensorimotor aspects of aerodigestive reflexes is altered in infants with HIE, and hypothermia may further modify such effects.

Physiology of esophageal sensorimotor malfunctions in neonatal neurological illness

We aimed to define the sensorimotor characteristics of aero-digestive reflexes evoked upon midesophageal provocations in neuropathology infants. Provocative esophageal motility testing was performed in 20 neuropathology infants and 10 controls at 42.3 ± 0.6 and 38.9 ± 0.9 wk postmenstrual age. Data from 1,073 infusions were examined for the sensory thresholds, response frequencies, response magnitude of upper esophageal sphincter (UES) contractile reflexes, lower esophageal sphincter (LES) relaxation reflexes, and peristaltic reflexes using mixed statistical models. Threshold volumes for air and liquid in neuropathology and control infants were similar for all reflexes. Graded air- and liquid volume-dependent UES contractile reflex, LES relaxation reflex, and peristaltic reflex frequency recruitment were present in neuropathology and control subjects for the media (P < 0.0001) and the reflexes (P < 0.0001). In neuropathology infants (vs. controls), UES contractile magnitude is higher (P < 0.0001); LES relaxation reflex occurred earlier (P = 0.008); LES nadir duration lasted longer (P = 0.006); secondary peristalsis is the chief method of esophageal clearance (P < 0.0001); pharyngeal swallows and deglutition apneas are less frequent (P = 0.001); proximal, midesophageal waveform magnitudes and duration are exaggerated (P < 0.008). UES contractile reflex was longer with liquid than air in both groups (P = 0.03). We concluded that 1) perception to midesophageal provocation remains preserved in neuropathology neonates; 2) sustained and exaggerated myogenic response from afferent activation is evident by increased excitatory efferent outputs to the UES and esophageal body and increased inhibitory efferent outputs to the LES; 3) dysfunctional regulation of pharyngeal swallowing and infrequent deglutition responses indicate the possibility of impaired descending modulation and central malfunctions of brainstem and vagal nuclei.

Pathophysiology of aerodigestive pulmonary disorders in the neonate

No test can provide a definitive diagnosis of aerodigestive disease. When interpreting tests, one should weigh the benefits and weaknesses of different technologies and methods, scientific appropriateness of the testing conditions, clinicopathologic correlation, and pharmacologic approaches. Gastroesophageal reflux disease (GERD) symptoms and airway symptoms can coexist, and they cannot be distinguished without specific testing and direct observations. Important aerodigestive disorders include dysphagia, GERD, and aggravation of airway injury due to malfunctions of swallowing or airway protection mechanisms. Objective evaluation of aerodigestive reflexes and symptom correlation may provide support for evidence-based personalized management of feeding and airway protection strategies.

Clinical Perspectives on Esophageal Disorders in Infants

Esophageal pathologies are complex and lend themselves to multivariable analysis before a definitive diagnosis can be considered. It is imperative that the clinician establish a methodology for selecting the appropriate technological assessment within scientific testing parameters to establish optimal clinicopathological presentation and determine best practice for patient care.

Impact of personalized feeding program in 100 NICU infants: pathophysiology-based approach for better outcomes

OBJECTIVES

In neonatal intensive care unit infants referred for home-tube feeding methods, we evaluated the effect of an innovative diagnostic and management approach on feeding outcomes at discharge and 1 year, by comparing data from historical controls; we hypothesized that clinical and aerodigestive motility characteristics at evaluation were predictive of feeding outcomes at discharge; we assessed the economic impact of feeding outcomes.

PATIENTS AND METHODS

Patients (N = 100) who were referred for development of long-term feeding management strategy at 46.4 ± 13.1 weeks' postmenstrual age were compared with 50 historical controls that received routine care. The focused approach included swallow-integrated pharyngoesophageal manometry, individualized feeding strategy, and prospective follow-up. Feeding success was defined as ability to achieve oral feedings at discharge and 1 year. Motility characteristics were evaluated in relation to feeding success or failure at discharge.

RESULTS

Higher feeding success was achieved in the innovative feeding program (vs historical controls) at discharge (51% vs 10%, P < 0.0001) and at 1 year (84.3% vs 42.9%, P < 0.0001), at a reduced economic burden (P < 0.05). Contributing factors to the innovative program's feeding success (vs feeding failure) were earlier evaluation and discharge (both P < 0.05), greater peristaltic reflex-frequency to provocation (P < 0.05), normal pharyngeal manometry (P < 0.05), oral feeding challenge success (P < 0.05), and suck-swallow-breath-esophageal swallow sequence (P < 0.05). Probability of feeding success demonstrated a prediction rate of 79.6%.

CONCLUSIONS

Short-term and long-term feeding outcomes in complex neonates can be significantly improved with innovative feeding strategies at a reduced cost. Clinical and aerodigestive motility characteristics were predictive of outcomes.

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

Electrocortical arousal (ECA) as an effect of visceral provocation or of its temporal relationships with aerodigestive reflexes in premature neonates is not known. We tested the hypothesis that esophageal provocation results in both esophageal reflex responses and ECAs during sleep and that ECAs are dependent on the frequency characteristics of esophageal neuromotor responses. We defined the spatiotemporal relationship of ECAs in relation to 1) spontaneous pharyngoesophageal swallow sequences and gastroesophageal reflux (GER) events and 2) sensory-motor characteristics of esophageal reflexes. Sixteen healthy premature neonates born at 27.9 ± 3.4 wk were tested at 36.8 ± 1.9 wk postmenstrual age. Ninety-five midesophageal and 31 sham stimuli were given in sleep during concurrent manometry and videopolysomnography. With stimulus onset as reference point, we scored the response latency, frequency occurrence and duration of arousals, peristaltic reflex, and upper esophageal sphincter contractile reflex (UESCR). Changes in polysomnography-respiratory patterns and esophageal sensory-motor parameters were scored by blinded observers. Significantly (for each characteristic listed, P < 0.05), swallow sequences were associated with arousals and sleep state changes, and arousals were associated with incomplete peristalsis, response delays to lower esophageal sphincter relaxation, and prolonged esophageal clearance. GER events (73.5%) provoked arousals, and arousals were associated with response delays to peristaltic reflexes or clearance, sleep state modification, and prolonged respiratory arousal. Midesophageal stimuli (54%) provoked arousals and were associated with increased frequency, prolonged latency, prolonged response duration of peristaltic reflexes and UESCR, and increased frequency of sleep state changes and respiratory arousals. In human neonates, ECAs are provoked upon esophageal stimulation; the sensory-motor characteristics of esophageal reflexes are distinct when accompanied by arousals. Aerodigestive homeostasis is defended by multiple tiers of aerodigestive safety mechanisms, and when esophageal reflexes are delayed, cortical hypervigilance (ECAs) occurs.

Impact of feeding strategies on the frequency and clearance of acid and nonacid gastroesophageal reflux events in dysphagic neonates

BACKGROUND

Feeding difficulties and gastroesophageal reflux (GER) are common problems in neonates. The authors hypothesize that GER could be influenced by feeding mechanics by evaluating the effects of feeding volumes, feeding durations, feeding flow rates, and caloric density on the chemical composition and clearance of GER in dysphagic neonates.

METHODS

Symptomatic dysphagic neonates (n = 35) underwent evaluation for suspected GER using pH-impedance methods.

RESULTS

The proportions of acid and nonacid GER were different during the first, second, and third postprandial hours (P < .0001). Prolonged feeding duration was significantly associated with decreased total, nonacid GER and BCT (P < .03). Significant positive correlations (P < .05) were detected between feeding flow rate vs frequency of total, nonacid GER and BCT. Significant positive correlation (P = .002) was noted between feeding volume and BCT. BCT decreased with each hourly interval (analysis of variance [ANOVA] P < .05); however, ACT increased with each hourly interval (ANOVA P = .05). Comparison between BCT and ACT at each postprandial hour is remarkable for longer ACT during the second and third hours after the initiation of feed (P ≤ .001). No significant correlation was noted between the milk types (breast milk or formula) or caloric density with regard to the GER characteristics. Oral-fed infants had more GER events than gavage-fed infants.

CONCLUSIONS

Prolonged feeding durations and slower flow rates are associated with decreased frequency of GER. Modification of feeding duration and flow rate can be a useful adjunct to ameliorate GER in dysphagic neonates.

Significance of gastroesophageal refluxate in relation to physical, chemical, and spatiotemporal characteristics in symptomatic intensive care unit neonates

Gastroesophageal reflux disease (GERD) is a frequent consideration in intensive care unit neonates. We tested the hypothesis that symptoms in GERD are dependent on the spatiotemporal and physicochemical characteristics of reflux events by evaluating the symptom sensitivity index (SSI) and symptom index (SI) in relation to the refluxate characteristics. Thirty symptomatic neonates (30.7 ± 0.8 wk gestation) were evaluated using manometry and pH-impedance methods. During 704.3 h of recordings, 2063 gastroesophageal reflux (GER) were observed; 54% of the GER were associated with symptoms. Defined by physical characteristics, there were 51.3% liquid, 29.1% gas, and 19.6% mixed GER. Defined by chemical characteristics, there were 48.5% acid and 51.5% nonacid GER. Defined by most proximal extent, 79.2% were supra-UES (upper esophageal sphincter) and 20.8% were infra-UES. Higher SSI was noted with pH-only events (p < 0.0001 versus pH-impedance events). Higher SI was noted with movement symptoms (versus sensory, p = 0.04). In a subset analysis, the frequencies of GER events, acid clearance time, and SSI were all greater in chronic lung disease versus none (p < 0.001). In conclusion, clinical significance of symptoms as measured by SSI and SI and characterization of spatial-temporal-physical-chemical nature of GER events as defined by pH-impedance methods clarifies the definition of GERD.