Pharyngoesophageal and cardiorespiratory interactions: potential implications for premature infants at risk of clinically significant cardiorespiratory events

Effects of Nasal Respiratory Support on Laryngeal and Esophageal Reflexes in Preterm Lambs

BACKGROUND

Significant cardiorespiratory events can be triggered in preterm infants as part of laryngeal chemoreflexes (LCRs) and esophageal reflexes (ERs). We previously showed that nasal continuous positive airway pressure (nCPAP) blunted the cardiorespiratory inhibition induced with LCRs. Therefore, we aimed to compare the effects of nCPAP and high-flow nasal cannulas (HFNC) on the cardiorespiratory events induced during LCRs and ERs. The hypothesis is that nCPAP but not HFNC decreases the cardiorespiratory inhibition observed during LCRs and ERs.

METHODS

Eleven preterm lambs were instrumented to record respiration, ECG, oxygenation, and states of alertness. LCRs and ERs were induced during non-rapid eye movement sleep in a random order under these conditions: nCPAP 6 cmH2O, HFNC 7 L/min, high-flow nasal cannulas 7 L/min at a tracheal pressure of 6 cmH2O, and no respiratory support.

RESULTS

nCPAP 6 cmH2O decreased the cardiorespiratory inhibition induced with LCRs, but not with ERs in preterm lambs. This blunting effect was less marked with HFNC 7 L/min, even when the tracheal pressure was maintained at 6 cmH2O.

CONCLUSIONS

nCPAP might be a treatment for cardiorespiratory events related to LCRs in newborns, either in the context of laryngopharyngeal refluxes or swallowing immaturity. Our preclinical results merit to be confirmed through clinical studies.

IMPACT

Laryngeal chemoreflexes can be responsible for significant cardiorespiratory inhibition in newborns, especially preterm. Nasal continuous positive airway pressure at 6 cmH2O significantly decreased this cardiorespiratory inhibition. High-flow nasal cannulas at 7 L/min had a lesser effect than nasal continuous positive airway pressure. Esophageal stimulation was responsible for a smaller cardiorespiratory inhibition, which was not significantly modified by nasal continuous positive airway pressure or high-flow nasal cannulas. Nasal continuous positive airway pressure should be tested for its beneficial effect on cardiorespiratory events related to laryngeal chemoreflexes in preterm newborns.

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.

The Irritable Infant in the Neonatal Intensive Care Unit: Risk Factors and Biomarkers of Gastroesophageal Reflux Disease

OBJECTIVES

To determine risk factors for arching/irritability in high-risk infants and examine the significance of comorbidity and gastroesophageal reflux (GER) characteristics.

STUDY DESIGN

Retrospective analysis of 24-hour pH-impedance studies of symptomatic infants in a neonatal intensive care unit (ICU) (n = 516, 30.1 ± 4.5 weeks of gestation, evaluated at 41.7 ± 3.2 weeks postmenstrual age) was conducted. Comparisons were made between infants with >72 vs ≤72 arching/irritability events per day. We characterized risk factors for arching/irritability along with clinical, pH-impedance, and outcome correlates.

RESULTS

Of 39 973 arching/irritability events and 42 155 GER events, the averages per day were 77.6 ± 41.0 and 81.7 ± 48.2, respectively. Acid reflux and impedance bolus characteristics were not significantly different between infants with >72 and ≤72 arching/irritability events (P ≥ .05). The odds ratios (ORs) and 95% confidence intervals (CIs) adjusted for postmenstrual age and weight at evaluation were significant for risk factors of preterm birth (2.3 [1.2-4.4]), moderate or severe neuropathology (2.0 [1.1-3.6]), and presence of oral feeding at testing (1.57 [1.07-2.30]).

CONCLUSIONS

Acid GER disease is unlikely the primary cause of arching/irritability and empiric treatment should not be used when arching/irritability is present. Prematurity and neurologic impairment may be more likely the cause of the arching/irritability. Arching/irritability may not be a concern in orally fed infants.

Wireless broadband acousto-mechanical sensing system for continuous physiological monitoring

The human body generates various forms of subtle, broadband acousto-mechanical signals that contain information on cardiorespiratory and gastrointestinal health with potential application for continuous physiological monitoring. Existing device options, ranging from digital stethoscopes to inertial measurement units, offer useful capabilities but have disadvantages such as restricted measurement locations that prevent continuous, longitudinal tracking and that constrain their use to controlled environments. Here we present a wireless, broadband acousto-mechanical sensing network that circumvents these limitations and provides information on processes including slow movements within the body, digestive activity, respiratory sounds and cardiac cycles, all with clinical grade accuracy and independent of artifacts from ambient sounds. This system can also perform spatiotemporal mapping of the dynamics of gastrointestinal processes and airflow into and out of the lungs. To demonstrate the capabilities of this system we used it to monitor constrained respiratory airflow and intestinal motility in neonates in the neonatal intensive care unit (n = 15), and to assess regional lung function in patients undergoing thoracic surgery (n = 55). This broadband acousto-mechanical sensing system holds the potential to help mitigate cardiorespiratory instability and manage disease progression in patients through continuous monitoring of physiological signals, in both the clinical and nonclinical setting.

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.

Precision caffeine therapy for apnea of prematurity and circadian rhythms: New possibilities open up

Caffeine is the globally consumed psychoactive substance and the drug of choice for the treatment of apnea of prematurity (AOP), but its therapeutic effects are highly variable among preterm infants. Many of the molecular underpinnings of the marked individual response have remained elusive yet. Interestingly, the significant association between Clock gene polymorphisms and the response to caffeine therapy offers an opportunity to advance our understanding of potential mechanistic pathways. In this review, we delineate the functions and mechanisms of human circadian rhythms. An up-to-date advance of the formation and ontogeny of human circadian rhythms during the perinatal period are concisely discussed. Specially, we summarize and discuss the characteristics of circadian rhythms in preterm infants. Second, we discuss the role of caffeine consumption on the circadian rhythms in animal models and human, especially in neonates and preterm infants. Finally, we postulate how circadian-based therapeutic initiatives could open new possibilities to promote precision caffeine therapy for the AOP management in preterm infants.

Symptom Scores and pH-Impedance: Secondary Analysis of a Randomized Controlled Trial in Infants Treated for Gastroesophageal Reflux

BACKGROUND AND AIMS

To evaluate and compare gastro-esophageal reflux (GER) symptom scores with pH-impedance and test the effects of acid-suppressive medications with or without feeding modifications on pH-impedance in high-risk infants.

METHODS

Infant Gastroesophageal Reflux Questionnaire Revised (I-GERQ-R) and 24-hour pH-impedance data were analyzed from 94 infants evaluated in a tertiary care setting for GER disease. Longitudinal data from 40 infants that received randomized GER therapy (proton pump inhibitor [PPI] with or without feeding modifications) for 4 weeks followed by 1-week washout were analyzed. Relationships between I-GERQ-R and pH-impedance metrics (acid reflux index, acid and bolus GER events, distal baseline impedance, and symptoms) were examined and effects of treatments compared.

RESULTS

(A) Correlations between I-GERQ-R and pH-impedance metrics were weak. (B) I-GERQ-R sensitivity, specificity, and positive predictive values were suboptimal when correlated with pH-impedance metrics. I-GERQ-R negative predictive value (NPV) was high for acid symptom-association probability (NPV = 84%) and distal baseline impedence (NPV = 86%) thresholds. (C) PPI with feeding modifications (vs PPI alone) did not alter pH-impedance metrics or symptom scores (P > .05); however, bolus clearance metrics worsened for both treatment groups (P < .05).

CONCLUSIONS

In high-risk infants (1) I-GERQ-R may be a helpful clinical screening tool to exclude acid-GER disease diagnosis and minimize unnecessary acid-suppressive treatment, but further testing is needed for diagnosis. (2) Acid-suppressive therapy with feeding modifications has no effect on symptom scores or pH-impedance metrics. Clearance of refluxate worsened despite PPI therapy, which may signal development of pharyngoesophageal dysmotility and persistence of symptoms. (3) Placebo-controlled trials are needed in high-risk infants with objective pH-impedance criteria to determine efficacy, safety, and underlying mechanisms. Clinicaltrials.gov ID: NCT02486263.

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.

Mechanisms and management considerations of parent-chosen feeding approaches to infants with swallowing difficulties: an observational study

Videofluoroscopy swallow studies (VFSS) and high-resolution manometry (HRM) methods complement to ascertain mechanisms of infant feeding difficulties. We hypothesized that: (a) an integrated approach (study: parent-preferred feeding therapy based on VFSS and HRM) is superior to the standard-of-care (control: provider-prescribed feeding therapy based on VFSS), and (b) motility characteristics are distinct in infants with penetration or aspiration defined as penetration-aspiration scale (PAS) score ≥ 2. Feeding therapies were nipple flow, fluid thickness, or no modification. Clinical outcomes were oral-feeding success (primary), length of hospital stay and growth velocity. Basal and adaptive HRM motility characteristics were analyzed for study infants. Oral feeding success was 85% [76-94%] in study (N = 60) vs. 63% [50-77%] in control (N = 49), p = 0.008. Hospital-stay and growth velocity did not differ between approaches or PAS ≥ 2 (all P > 0.05). In study infants with PAS ≥ 2, motility metrics differed for increased deglutition apnea during interphase (p = 0.02), symptoms with pharyngeal stimulation (p = 0.02) and decreased distal esophageal contractility (p = 0.004) with barium. In conclusion, an integrated approach with parent-preferred therapy based on mechanistic understanding of VFSS and HRM metrics improves oral feeding outcomes despite the evidence of penetration or aspiration. Implementation of new knowledge of physiology of swallowing and airway protection may be contributory to our findings.

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.

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.

Effects of effortful swallowing on cardiac autonomic control in individuals with neurogenic dysphagia: a prospective observational analytical study

Considering that neurogenic oropharyngeal dysphagia is a prevalent condition with or without cardiac disease we should contemplate issues surrounding cardiovascular difficulties during rehabilitation. This study aims to evaluate the effects of effortful swallowing maneuver (ESM) on heart rate variability (HRV) in subjects with neurogenic oropharyngeal dysphagia. We studied 22 individuals [8 Stroke and 14 Parkinson Disease (PD) subjects aged between 41 and 75 years old] with neurogenic oropharyngeal dysphagia regardless of gender. HRV was assessed under two circumstances: spontaneous swallowing versus ESM. Surface electromyography of the suprahyoid muscles was undertaken to measure the swallowing muscle excitation, which then confirmed higher muscle activity during ESM. We attained no changes in HRV between the two swallowing events [HR: spontaneous swallowing 78.68 ± 13.91 bpm vs. ESM 102.57 ± 107.81 bpm, p = 0.201; RMSSD (root-mean square of differences between adjacent normal RR intervals in a time interval): spontaneous swallowing 16.99 ± 15.65 ms vs. ESM 44.74 ± 138.85 ms, p = 0.312; HF (high frequency): spontaneous swallowing 119.35 ± 273 ms² vs. ESM 99.83 ± 194.58 ms², p = 0.301; SD1 (standard deviation of the instantaneous variability of the beat-to-beat heart rate): spontaneous swallowing 12.02 ± 1.07 ms vs. ESM 31.66 ± 98.25 ms, p = 0.301]. The effortful swallowing maneuver did not cause clinically significant changes in autonomic control of HR in this group of subjects with oropharyngeal dysphagia.

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.

Approach to Feeding Difficulties in Neonates and Infants: A Comprehensive Overview

Deglutition disorders (DD) can be transient and considered as physiologic during normal maturation. However, when oral feeding milestones are impaired and bothersome symptoms and aerodigestive consequences are associated, it is interpreted as DD with varying specific entities, such as feeding difficulties, swallowing disorders, aerodigestive illness, and aspiration syndromes. Symptoms related to DD are heterogeneous and managed empirically. This article clarifies current controversies, explains the potential role of safe feeding and physiologic and pathophysiologic perspectives, and highlights current advances in the field. Evidence basis for diagnostic strategies is discussed, and involves evaluation for structure and function tests, and nutrition and feeding assessment.

Feeding and Swallowing Difficulties in Neonates: Developmental Physiology and Pathophysiology

Development of enteral and oral feeding milestones in infants is intricately linked to physiologic maturation of the gastrointestinal tract and its complex interplay with cardiorespiratory and central nervous system control and coordination. Assessment of an infant's developmental skills and maturation can guide us with targeted management approaches and prediction of feeding outcomes. In this article, we review and summarize the developmental aspects of oral feeding and swallowing physiology, and current understanding of the pathophysiological changes associated with feeding difficulties in infants.

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.