Development of pharyngo-esophageal physiology during swallowing in the preterm infant

Effect of different tube feeding methods on gastroesophageal reflux features in preterm infants: a pH-impedance monitoring study

A stepwise approach is currently considered the best choice to manage gastroesophageal reflux (GER) in preterm infants. This study aimed to evaluate the effect of different tube feeding techniques on GER frequency and features in symptomatic tube-fed preterm neonates. Tube-fed infants < 34 weeks' gestation were eligible for this prospective, bicentric, cross-over study if, due to GER symptoms, they underwent a diagnostic 24-h combined pH and multiple intraluminal impedance (pH-MII) monitoring. During the monitoring period, each infant received the same feeding cycle, repeated twice: continuous tube feeding, bolus feeding followed by tube feeding permanence and by tube feeding removal. The impact of these three feeding modalities on pH-MII GER features was assessed. Thirty-one infants were enrolled. Despite a low number of reflux episodes, a significant decrease in total GERs (P < 0.001), in GERs detected by pH monitoring (P < 0.001), and in both acid and non-acid GERs detected by MII (P < 0.001 and P = 0.009, respectively) was observed in association with continuous feeding compared to bolus feeds, followed or not by tube feeding removal. Compared to continuous feeding, both bolus feeding modalities were associated with a significantly higher number of proximal GERs (P < 0.001). No difference in any pH-MII parameter was observed in relation to tube feeding persistence after bolus feeding administration.

CONCLUSIONS

Continuous feeding and boluses may have a different impact on pH-MII GER features in symptomatic tube-fed preterm infants, whereas the permanence of the feeding tube across LES did not seem to worsen GER indexes.

WHAT IS KNOWN

• Due to the functional and anatomical immaturity of the gastrointestinal tract, gastroesophageal reflux (GER) is common in preterm infants. • A stepwise therapeutical approach which firstly undertakes conservative strategies is the most advisable choice to avoid potentially harmful pharmacological overtreatments in the preterm population.

WHAT IS NEW

• Continuous feeding and boluses may have a different impact on GER features assessed by pH-MII monitoring in tube-fed preterm infants. • The permanence of the feeding tube during or after the feeding period did not seem to worsen GER occurrence. • By reducing GER features, especially acid GER, continuous feeding may potentially contribute to limit the need for antiacid medications in this population.

Premature Babies Can Be Cared for in the Maternity Ward without an Increased Risk and Discharged with a Feeding Tube If Necessary

In general, premature babies are discharged home when they reach full self-feeding. We established a discharge management protocol which allows for discharging late preterm babies with a feeding tube if necessary. This retrospective study included 108 preterm infants (34+ weeks) born in 2019 and 2020. The preterm infants discharged with a feeding tube (n = 32) were born at 35.23 weeks' gestation (±0.884), with a birth weight of 2423 g (±375.1), and were discharged at 7.22 days (±3.63) and had a weight of 3466 g (±591.3) at the first outpatient visit around the expected birth date. The preterm infants discharged without a feeding tube were born at 35.97 weeks' gestation (±0.702) with a birth weight of 2589 g (±424.84), discharged home at 6.82 days (±7.11) and a weight of 3784 g (±621.8) at the first outpatient visit. The gestational week and birth weight were statistically significantly different between the groups, with a p-value of <0.001 for each, and the length of hospital stay (p = 0.762) and weight at follow-up (p = 0.064) did not significantly differ. No infant required tube-feeding at the time of the first outpatient visit, i.e., the time of expected birth. Therefore, with well-thought-out management, it is possible and safe to discharge preterm infants home with a feeding tube.

Differences in the swallowing process of newborns and healthy preterm infants: first results with a non-invasive bioimpedance and electromyography measurement system

PURPOSE

Preterm infants (PI) have difficulty coordinating sucking, swallowing and breathing, and there is a risk of aspiration. The causes of this are not yet sufficiently understood. The aim of this study was to test a novel measurement device to measure breathing and pharyngeal processes involved in swallowing externally in everyday life to identify possible differences in neonates (NB) and PI.

METHODS

Forty healthy NB were studied at 4-8 weeks of age (mean: 6.7 weeks) and 20 healthy PI (mean gestational age 30.5 weeks) at postmenstrual age (PMA) 34/35 weeks (mean PMA 35.1 weeks) during a single feeding. Surface electrodes were used to measure bioimpedance and electromyography reflecting swallow-related changes in the pharynx and muscle activation of the tongue and submental muscles. A respiratory belt was combined with recording of the depth of chest movements and the occurrence of pauses in breathing.

RESULTS

Velocity and extent of pharyngeal closure did not differ significantly across the feeding period (velocity: p=0.09, closure: p=0.17), but during the first two suck-swallow bursts PI had greater velocity (p<0.001*) and extent of pharyngeal closure (p=0.004*) than NB. The duration of swallowing phases was significantly longer in PIs (p<0.001*), their muscle activation decreased faster (p<0.001*), and they had more pauses in breathing than NBs.

CONCLUSIONS

The novel measurement device allowed, for the first time in everyday life, the measurement of factors influencing swallowing and breath-swallow coordination in NBs and PIs. PIs showed differences from NBs most likely due to differences in muscle strength and condition.

A Review of Histamine-2 Receptor Antagonist and Proton Pump Inhibitor Therapy for Gastroesophageal Reflux Disease in Neonates and Infants

Proton pump inhibitors (PPI) and histamine-2 receptor antagonists (H2RA) are commonly used medications in neonates and infants for the treatment of gastroesophageal reflux disease (GERD), especially in neonatal intensive care units (NICUs). A literature review was conducted to evaluate the efficacy and safety of histamine-2 receptor antagonists (H2RAs) and proton pump inhibitors (PPIs) in preterm neonates, term neonates, and infants. A total of 27 studies were included in this review. Antacid medications in studies have consistently shown positive pharmacodynamic effects, including increasing gastric pH, reducing the reflux index, and reducing the number of acidic reflux events. The benefit found in placebo-controlled trials are limited exclusively to these surrogate outcomes. The actual clinically salient outcomes which H2RAs and PPIs are used for, such as reduction in GERD symptoms, especially irritability and improved feed tolerance and weight gain, have consistently shown no clinical benefit. H2RAs and PPIs appear to be extremely well tolerated by the neonatal and infant populations, which would mimic our experience with these medications in our unit. The available data from large, retrospective cohort and case-control studies paint a much more concerning picture regarding the potential for an increased risk in the development of allergies, anaphylactic reactions, necrotizing enterocolitis (NEC), other nosocomial infections, and lower respiratory tract infections. Given the risks associated with and lack of clinical effectiveness of both H2RAs and PPIs, use of these medications should be limited to specific clinical situations. Further studies are required to determine whether antacid pharmacologic therapy might benefit certain neonates and infants, such as those with complex medical issues.

Preterm infant cues during breastfeeding and its measurement: A scoping review

Background

Preterm infants display certain behaviors to communicate their needs, known as preterm infant cues. However, the existing research on preterm infant cues primarily draws from studies conducted on bottle-fed infants rather than breastfed infants.

Objective

This study aimed to investigate the concept of preterm infant cues during breastfeeding and its appropriate instruments.

Design

A scoping review.

Data Sources

The articles published up to January 2022 were searched from multiple sources from EBSCOhost Web, namely CINAHL Plus with Full Text, MEDLINE, ERIC, and E-Journals.

Review Methods

The articles retrieved for this review were screened using PICO (Population, Intervention, Comparison, and Outcomes) format. Preferred Reporting Items for Systematic Reviews (PRISMA) checklist was used in selecting the articles, and Joanna Briggs Institute Critical Appraisal was utilized by two independent authors to assess the articles' quality. A descriptive method was used to analyze the data.

Results

The initial review stage found 183 potential articles, but only four satisfied the criteria. The notion of preterm infant cues during breastfeeding is centered on the actions of preterm infants while positioned on their mother's chest. These feeding cues are identifiable before, during, and after breastfeeding and include cues for hunger, self-regulation, stress, satiation, approach, avoidance, and sucking quality. To effectively recognize these cues, tools such as the Preterm Infants Cues Coding System (PFCCS), Infant Driven Scale (IDS), Newborn Individualized Developmental Care and Assessment Program (NIDCAP), and Preterm Breastfeeding Behavior Scale (PIBBS) can be utilized.

Conclusion

The study findings highlight the importance of recognizing preterm infant cues during breastfeeding to facilitate proper feeding and developmental care. Observational studies have proven to be an effective means of observing these cues during breastfeeding. By leveraging the cues identified in this review alongside tools such as PFCCS, IDS, NIDCAP, and PIBBS, nurses can accurately interpret preterm infants' breastfeeding cues in neonatal care settings of all levels. This, in turn, can aid in developing care plans that promote better feeding ability outcomes.

Characterizing Esophageal Motility in Neonatal Intensive Care Unit Patients Using High Resolution Manometry

OBJECTIVE

To characterize esophageal motility and esophago-gastric junction (EGJ) function during feeding in neonatal intensive care unit (NICU) patients.

PATIENTS AND METHODS

High resolution manometry with impedance (HRIM) was used to investigate esophageal motility and EGJ function in patients admitted to the NICU. Twenty-eight preterm born infants with bronchopulmonary dysplasia (BPD), 12 born with isolated congenital diaphragmatic hernia (iCDH), and 10 with esophageal atresia (EA) were included. Thirteen healthy infants were included as controls. Esophageal motility and EGJ function were analyzed using objective esophageal bolus transport parameters.

RESULTS

Normal esophageal peristaltic wave patterns were observed in all investigated infants without EA. Nine of 10 patients with EA presented with abnormal esophageal motor wave patterns. A total of 224 nutritive swallows were analyzed (controls, n = 48; BPD, n = 96; iCDH, n = 60; EA, n = 20). Infants with BPD and iCDH had similar distal contractile strength (DCI) compared to healthy controls, while in patients with EA, DCI was significantly lower (Kruskal-Wallis test, p = 0.001). In most infants, EGJ relaxation after swallowing was unaffected. EGJ barrier function, in terms of EGJ-contractile integral, also appeared well-developed and did not differ significantly among patient groups.

CONCLUSIONS

We conclude that esophageal motility studies using pressure-impedance analysis are feasible in young infants. Bolus transport mechanisms following nutritive swallows appeared well-established in all investigated infants with the exception of those with EA. EGJ relaxation was also functional after deglutition and EGJ function as an anti-reflux barrier appeared well-developed in all investigated NICU groups.

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.

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.

Pharyngeal and upper esophageal sphincter motor dynamics during swallow in children

BACKGROUND

Motor abnormalities of pharyngeal contraction or upper esophageal sphincter (UES) relaxation can lead to swallowing problems.

METHODS

We reviewed high-resolution esophageal manometry of children ≤18 years and classified into two groups based on the results of videofluoroscopic study of swallow (VFSS), as normal or abnormal. The UES metrics (integrated relaxation pressure [IRP], resting pressure [URP], and nadir pressure [UNP]), as well as peak pharyngeal pressure (velopharyngeal and meso-hypopharyngeal), were analyzed.

RESULTS

UES metrics: There were 142 and 19 subjects in the normal and abnormal groups, respectively. In the normal group, the median UES-IRP at 0.2, 0.4, 0.6, 0.8 seconds, URP, and UNP were 1.0, 4.0, 11.0, 18.0, 53.5, and -1.0 mm Hg while in the abnormal group were 10.0, 13.0, 21.0, 25.5, 47.0, and 8.0 mm Hg. The UES-IRP at 0.2, 0.4, 0.6 seconds, and UNP was significantly higher in the abnormal group. Pharyngeal metrics: We included 58 subjects in normal and 10 subjects in the abnormal group. The median of peak velopharyngeal and meso-hypopharyngeal pressures were lower in the abnormal group; 188.50 vs 210.50, P = .185 and 110.00 vs 144.75 mm Hg, P = .065.

CONCLUSIONS AND INFERENCES

The UES-IRP was lower than adults, URP was higher than preterm but less than adults, and UNP was lower than neonates but similar to adults. The pharyngeal pressures were higher than those reported for neonates and adults. Our data indicate that motor dynamics of swallowing may change from neonates to adulthood and reflect a maturational process. The subjects with abnormal VFSS had significantly higher UES-IRP and UNP compared to normal VFSS.

Abnormal Nutritive Sucking as an Indicator of Neonatal Brain Injury

A term neonate is born with the ability to suck; this neuronal network is already formed and functional by 28 weeks gestational age and continues to evolve into adulthood. Because of the necessity of acquiring nutrition, the complexity of the neuronal network needed to suck, and neuroplasticity in infancy, the skill of sucking has the unique ability to give insight into areas of the brain that may be damaged either during or before birth. Interpretation of the behaviors during sucking shows promise in guiding therapies and how to potentially repair the damage early in life, when neuroplasticity is high. Sucking requires coordinated suck-swallow-breathe actions and is classified into two basic types, nutritive and non-nutritive. Each type of suck has particular characteristics that can be measured and used to learn about the infant's neuronal circuitry. Basic sucking and swallowing are present in embryos and further develop to incorporate breathing ex utero. Due to the rhythmic nature of the suck-swallow-breathe process, these motor functions are controlled by central pattern generators. The coordination of swallowing, breathing, and sucking is an enormously complex sensorimotor process. Because of this complexity, brain injury before birth can have an effect on these sucking patterns. Clinical assessments allow evaluators to score the oral-motor pattern, however, they remain ultimately subjective. Thus, clinicians are in need of objective measures to identify the specific area of deficit in the sucking pattern of each infant to tailor therapies to their specific needs. Therapeutic approaches involve pacifiers, cheek/chin support, tactile, oral kinesthetic, auditory, vestibular, and/or visual sensorimotor inputs. These therapies are performed to train the infant to suck appropriately using these subjective assessments along with the experience of the therapist (usually a speech therapist), but newer, more objective measures are coming along. Recent studies have correlated pathological sucking patterns with neuroimaging data to get a map of the affected brain regions to better inform therapies. The purpose of this review is to provide a broad scope synopsis of the research field of infant nutritive and non-nutritive feeding, their underlying neurophysiology, and relationship of abnormal activity with brain injury in preterm and term infants.

Sucking versus swallowing coordination, integration, and performance in preterm and term infants

Mammalian infants must be able to integrate the acquisition, transport, and swallowing of food to effectively feed. Understanding how these processes are coordinated is critical, as they have differences in neural control and sensitivity to perturbation. Despite this, most studies of infant feeding focus on isolated processes, resulting in a limited understanding of the role of sensorimotor integration in the different processes involved in infant feeding. This is especially problematic in the context of preterm infants, as they are considered to have pathophysiological brain development and often experience feeding difficulties. Here, we use an animal model to study how the different properties of food acquisition, transport, and swallowing differ between term and preterm infants longitudinally through infancy to understand which processes are sensitive to variation in the bolus being swallowed. We found that term infants are better able to acquire milk than preterm infants, and that properties of acquisition are strongly correlated with the size of the bolus being swallowed. In contrast, behaviors occurring during the pharyngeal swallow, such as hyoid and soft palate movements, show little to no correlation with bolus size. These results highlight the pathophysiological nature of the preterm brain and also demonstrate that behaviors occurring during oral transport are much more likely to respond to sensory intervention than those occurring during the "pharyngeal phase."NEW & NOTEWORTHY Physiological maturation of infant feeding is clinically and developmentally significant, but seldom examined as an integrated function. Using longitudinal high-speed videofluoroscopic data, we found that properties of sucking, such as the length of the suck, are more sensitive to swallow physiology than those associated with the pharyngeal swallow itself, such as hyoid excursion. Prematurity impacted the function and maturation of the feeding system, resulting in a physiology that fundamentally differs from term infants by weaning.

Preterm Birth Impacts the Timing and Excursion of Oropharyngeal Structures during Infant Feeding

Swallowing in mammals requires the precise coordination of multiple oropharyngeal structures, including the palatopharyngeal arch. During a typical swallow, the activity of the palatopharyngeus muscle produces pharyngeal shortening to assist in producing pressure required to swallow and may initiate epiglottal flipping to protect the airway. Most research on the role of the palatopharyngeal arch in swallowing has used pharyngeal manometry, which measures the relative pressures in the oropharynx, but does not quantify the movements of the structures involved in swallowing. In this study, we assessed palatopharyngeal arch and soft palate function by comparing their movements in a healthy population to a pathophysiological population longitudinally through infancy (term versus preterm pigs). In doing so, we test the impact of birth status, postnatal maturation, and their interaction on swallowing. We tracked the three-dimensional (3D) movements of radiopaque beads implanted into relevant anatomical structures and recorded feeding via biplanar high-speed videofluoroscopy. We then calculated the total 3D excursion of the arch and soft palate, the orientation of arch movement, and the timing of maximal arch constriction during each swallow. Soft palate excursion was greater in term infants at both 7 and 17 days postnatal, whereas arch excursion was largely unaffected by birth status. Maximal arch constriction occurred much earlier in preterm pigs relative to term pigs, a result that was consistent across age. There was no effect of postnatal age on arch or soft palate excursion. Preterm and term infants differed in their orientation of arch movement, which most likely reflects both differences in anatomy and differences in feeding posture. Our results suggest that the timing and coordination of oropharyngeal movements may be more important to feeding performance than the movements of isolated structures, and that differences in the neural control of swallowing and its maturation in preterm and term infants may explain preterm swallowing deficits.

Characterization of esophageal motility and esophagogastric junction in preterm infants with bronchopulmonary dysplasia

BACKGROUND

To characterize esophageal motility and function of the esophagogastric junction (EGJ) in preterm infants with bronchopulmonary dysplasia (BPD).

METHODS

High-resolution manometry with impedance was used to investigate esophageal motility and EGJ function in 28 tube-fed preterm infants with BPD. Patients with BPD were studied at term age during oral feeding. Thirteen healthy term-aged infants were included as controls. Esophageal analysis derived objective measures to evaluate esophageal contractile vigor, bolus distension pressure, EGJ relaxation, and EGJ barrier function (in rest and during respiration). In addition, we investigated the effect of BPD severity on these measures.

KEY RESULTS

A total of 140 nutritive swallows were analyzed (BPD, n = 92; controls, n = 48). Normal esophageal peristaltic wave patterns were observed in all infants. BPD patients had higher distal contractile esophageal strength compared with controls (Kruskal-Wallis (KW) P = .048), and their deglutitive EGJ relaxation was comparable to controls. Severe BPD patients showed higher bolus distension pressures, higher EGJ resting pressures, and increased EGJ contractile integrals compared with mild BPD patients (Mann-Whitney U P = .009, KW P = .012 and KW P = .028, respectively).

CONCLUSIONS AND INFERENCES

Preterm infants with BPD consistently present with normal peristaltic esophageal patterns following nutritive liquid swallows. The EGJ barrier tone and relaxation pressure appeared normal. In general, infants with BPD do not have altered esophageal motor function. There is however evidence for increased flow resistance at the EGJ in severe BPD patients possibly related to an increased contractility of the diaphragm.

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.

Swallow Safety is Determined by Bolus Volume During Infant Feeding in an Animal Model

Feeding difficulties are especially prevalent in preterm infants, although the mechanisms driving these difficulties are poorly understood due to a lack of data on healthy infants. One potential mechanism of dysphagia in adults is correlated with bolus volume. Yet, whether and how bolus volume impacts swallow safety in infant feeding is unknown. A further complication for safe infant swallowing is recurrent laryngeal nerve (RLN) injury due to patent ductus arteriosus surgery, which exacerbates the issues that preterm infants face and can increase the risk of dysphagia. Here, we used a validated animal model feeding freely to test the effect of preterm birth, postnatal maturation and RLN lesion and their interactions on swallow safety. We also tested whether bolus size differed with lesion or birth status, and the relationship between bolus size and swallow safety. We found very little effect of lesion on swallow safety, and preterm infants did not experience more penetration or aspiration than term infants. However, term infants swallowed larger boluses than preterm infants, even after correcting for body size. Bolus size was the primary predictor of penetration or aspiration, with larger boluses being more likely to result in greater degrees of dysphagia irrespective of age or lesion status. These results highlight that penetration and aspiration are likely normal occurrences in infant feeding. Further, when comorbidities, such as RLN lesion or preterm birth are present, limiting bolus size may be an effective means to reduce incidences of penetration and aspiration.

The effect of preterm birth, recurrent laryngeal nerve lesion, and postnatal maturation on hyoid and thyroid movements, and their coordination in infant feeding

Movements of the hyoid and thyroid are critical for feeding. These structures are often assumed to move in synchrony, despite evidence that neurologically compromised populations exhibit altered kinematics. Preterm infants are widely considered to be a neurologically compromised population and often experience feeding difficulties, yet measuring performance, and how performance matures in pediatric populations is challenging. Feeding problems are often compounded by complications arising from surgical procedures performed to ensure the survival of preterm infants, such as damage to the recurrent laryngeal nerve (RLN) during patent ductus arteriosus correction surgery. Here, we used a validated infant pig model for infant feeding to test how preterm birth, postnatal maturation, and RLN lesion interact to impact hyoid and thyroid excursion and their coordination. We filmed infant pigs when feeding using videofluorscopy at seven days old (1-2 months human equivalent) and 17 days old (6-9 months human equivalent) and tracked movements of the hyoid and thyroid on both days. We found that preterm birth impacted the coordination between hyoid and thyroid movements, but not their actual excursion. In contrast, excursion of the two structures increased with postnatal age in term and preterm pigs. RLN lesion decreased thyroid excursion, and primarily impacted hyoid movements by increasing variation in hyoid excursion. This work demonstrates that RLN lesion and preterm birth have distinct, but pervasive effects on feeding performance in infants, and suggest that interventions targeted towards reducing dysphagia should be prescribed based off the etiology driving dysphagia, rather than the prognosis of dysphagia.

Premature birth impacts bolus size and shape through nursing in infant pigs

BACKGROUND

The formation of a bolus of food is critical for proper feeding function, and there is substantial variation in the size and shape of a bolus prior to a swallow. Preterm infants exhibit decreased abilities to acquire and process food, but how that relates to their bolus size and shape is unknown. Here, we test two hypotheses: (1) that bolus size and shape will differ between term and preterm infants, and (2) bolus size and shape will change longitudinally through development in both term and preterm infants.

METHODS

To test these hypotheses, we measured bolus size and shape in preterm and term infant pigs longitudinally through nursing using high-speed videofluoroscopy.

RESULTS

Preterm infant pigs swallowed smaller volumes of milk. Although term infants increased the amount of milk per swallow as they aged, preterm infants did not. These changes in bolus volume were also correlated with changes in bolus shape; larger boluses became more elongate as they better filled the available anatomical space of the valleculae.

CONCLUSIONS

These results suggest that preterm birth reduces the ability of preterm pigs to increase bolus size as they grow, affecting development in this fragile population. These results highlight that studies on term infant feeding may not translate to preterm infants.

A Guide to Feeding Term and Preterm Newborns

The management of feeding term and preterm newborns encompasses knowing the physiologic mechanics of nutritive feeding and requirements for good somatic and neurodevelopmental growth. Feeding in newborns can be fraught with challenges that each individual infant-family unit presents. Management is multifactorial and requires fluidity as the infant progresses. Pediatricians are tasked with one of the most important responsibilities in the newborn period-partnering with families to ensure optimal feeding regimen and infant growth. This article's aim is to outline general recommendations on evidence-based feeding practices in term and preterm infants with a goal to help guide pediatricians create an optimal individualized feeding regimen and address some known hurdles. [Pediatr Ann. 2020;49(2):e71-e76.].

Preterm birth disrupts the development of feeding and breathing coordination

All mammals must breathe and breathe continuously from birth. Similarly, all mammals, including infants, have high functional demands for feeding. However, the pathway that food takes through the pharynx interrupts respiration. The coordination between swallowing and breathing is therefore critical for all infant mammals. Clinically, this coordination differs between term and preterm infants. However, the neurological mechanisms underlying this coordination and how it matures as infants grow are poorly understood. Here, we integrate high-resolution data from multiple physiologic processes across a longitudinal time frame to study suck-swallow-breathe dynamics in a preterm animal model, the infant pig. In doing so, we test the hypothesis that preterm birth will have an impact on some, but not all, behaviors associated with suck-swallow-breath performance. We hypothesize that coordination will be disrupted, reflecting incomplete connections in the brainstem. We found that preterm pigs became rhythmic and mature in sucking and swallowing behaviors, suggesting substantial postnatal maturation in the coordination of these behaviors. However, their ability to coordinate swallowing and breathing never developed. These results have implications for the nature of clinical care of human infants, as well as for how feeding processes develop in mammals. Clinically, they provide a foundation for developing interventions for preterm infants. Additionally, these results suggest that the lack of coordination between swallowing and breathing may be a significant factor in determining the minimum gestation time across mammals. NEW & NOTEWORTHY Preterm infants face a variety of challenges associated with safe feeding, but obtaining high-resolution longitudinal data to understand these challenges in humans is challenging. We used a pig model to acquire high-speed videofluoroscopic and respiratory inductance plethysmograph data throughout the nursing period to show that preterm birth does not have substantial impacts on the ability of infants to perform isolated behaviors. However, it does decrease the ability of preterm infants to coordinate among behaviors during feeding.

Know the Flow: Milk Flow Rates From Bottle Nipples Used in the Hospital and After Discharge

BACKGROUND

Milk flow rate may play an important role in an infant's ability to safely and efficiently coordinate sucking, swallowing, and breathing during feeding.

PURPOSE

To test milk flow rates from bottle nipples used in the hospital and after discharge.

METHODS

Bottle nipples used in hospitals (10 unique types) and available nationwide at major retailers (15 unique types) were identified. For each of the 25 nipple types, 15 nipples of that type were tested by measuring the amount of infant formula extracted in 1 minute by a breast pump. Mean milk flow rate (mL/min) and coefficient of variation (CV) were calculated for each nipple type. Comparisons between nipple types were made within brand and within category (eg, Slow, Standard). A cluster analysis was conducted to identify nipples of comparable flow.

RESULTS

A total of 375 individual nipples were tested. Milk flow rates varied widely, from 0.86 to 37.61 mL/min. There was also a wide range of CVs, from 0.03 to 0.35. Packing information did not accurately reflect the flow rates of bottle nipples. The cluster analysis revealed 5 clusters of nipples, with flow rates from Extra Slow to Very Fast.

IMPLICATIONS FOR PRACTICE

These data can be used to guide decisions regarding nipples to use for feeding infants with medical complexity in the hospital and after discharge.

IMPLICATIONS FOR RESEARCH

Research on infant feeding should consider the flow rate and variability of nipples used, as these factors may impact findings.

Milk Flow Rates from bottle nipples used after hospital discharge

PURPOSE

To test the milk flow rates and variability in flow rates of bottle nipples used after hospital discharge.

STUDY DESIGN AND METHODS

Twenty-six nipple types that represented 15 common brands as well as variety in price per nipple and store location sold (e.g., Babies R' Us, Walmart, Dollar Store) were chosen for testing. Ten of each nipple type (n = 260 total) were tested by measuring the amount of infant formula expressed in 1 minute using a breast pump. Mean milk flow rate (mL/min) and coefficient of variation (CV) were calculated. Flow rates of nipples within brand were compared statistically.

RESULTS

Milk flow rates varied from 1.68 mL/min for the Avent Natural Newborn Flow to 85.34 mL/min for the Dr. Brown's Standard Y-cut. Variability between nipple types also varied widely, from .03 for the Dr. Brown's Standard Level 3 to .37 for MAM Nipple 1 Slow Flow.

CLINICAL IMPLICATIONS

The extreme range of milk flow rates found may be significant for medically fragile infants being discharged home who are continuing to develop oral feeding skills. The name of the nipple does not provide clear information about the flow rate to guide parents in decision making. Variability in flow rates within nipples of the same type may complicate oral feeding for the medically fragile infant who may not be able to adapt easily to change in flow rates. Both flow rate and variability should be considered when guiding parents to a nipple choice.

Maturation of the Coordination Between Respiration and Deglutition with and Without Recurrent Laryngeal Nerve Lesion in an Animal Model

The timing of the occurrence of a swallow in a respiratory cycle is critical for safe swallowing, and changes with infant development. Infants with damage to the recurrent laryngeal nerve, which receives sensory information from the larynx and supplies the intrinsic muscles of the larynx, experience a significant incidence of dysphagia. Using our validated infant pig model, we determined the interaction between this nerve damage and the coordination between respiration and swallowing during postnatal development. We recorded 23 infant pigs at two ages (neonatal and older, pre-weaning) feeding on milk with barium using simultaneous high-speed videofluoroscopy and measurements of thoracic movement. With a complete linear model, we tested for changes with maturation, and whether these changes are the same in control and lesioned individuals. We found (1) the timing of swallowing and respiration coordination changes with maturation; (2) no overall effect of RLN lesion on the timing of coordination, but (3) a greater magnitude of maturational change occurs with RLN injury. We also determined that animals with no surgical intervention did not differ from animals that had surgery for marker placement and a sham procedure for nerve lesion. The coordination between respiration and swallowing changes in normal, intact individuals to provide increased airway protection prior to weaning. Further, in animals with an RLN lesion, the maturation process has a larger effect. Finally, these results suggest a high level of brainstem sensorimotor interactions with respect to these two functions.

Temporal Trends of Pediatric Dysphagia in Hospitalized Patients

The objective of this study was to determine temporal trends of dysphagia diagnoses in hospitalized children. This is a retrospective observational study from the 1997-2012 Kids' Inpatient Database (KID) conducted in the setting of weighted hospitalizations in a KID participating center. More than 6 million pediatric admissions were captured in each triennial KID report. Main outcomes included triennial rates of dysphagia diagnosis in hospitalized pediatric patients, and secondary outcomes included rates of dysphagia in premature and low-birthweight infants. Dysphagia diagnoses were coded in 5107/6607653 (0.08%) of these admissions in 1997, rising to 27,464/6,675,222 (0.41%) in 2012 (p < 0.001). The portion of these diagnoses in premature neonates has been increasing over time from 162/9551 (1.7%) in 2003 to 1027/27,464 (3.7%) by 2012 (p < 0.001). Similarly, low-birthweight children constituted 40/5107 (0.8%) of dysphagia diagnoses in 1997, a number that increased to 762/27,464 (2.8%) in 2012. Rates of dysphagia are increasing nationally, particularly in premature and low-birthweight infants, which may represent an increase alongside other neuroanatomic abnormalities. This growing problem illustrates the need for better data on the comparative efficacy of diagnostic and treatment modalities.

Motility disorders in infants

Gastrointestinal motility disorders are common in the pediatric population and may affect the entire gastrointestinal tract and can vary from mild to severe conditions. They may clinically manifest as gastro-esophageal reflux symptoms, feeding difficulties and failure to thrive, constipation and diarrhea amongst others. This review first highlights the embryologic development of the gastrointestinal tract, after which the prenatal and neonatal development of gastrointestinal motility is discussed. Normal motility patterns as seen in (preterm) infants are described as a background for the discussion of the most common congenital and acquired motility disorders in infancy. This review specifically focuses on the role of preterm birth on the development of these disorders.

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.

Characterization and mechanisms of the pharyngeal swallow activated by stimulation of the esophagus

Stimulation of the esophagus activates the pharyngeal swallow response (EPSR) in human infants and animals. The aims of this study were to characterize the stimulus and response of the EPSR and to determine the function and mechanisms generating the EPSR. Studies were conducted in 46 decerebrate cats in which pharyngeal, laryngeal, and esophageal motility was monitored using EMG, strain gauges, or manometry. The esophagus was stimulated by balloon distension or luminal fluid infusion. We found that esophageal distension increased the chance of occurrence of the EPSR, but the delay was variable. The chance of occurrence of the EPSR was related to the position, magnitude, and length of the stimulus in the esophagus. The most effective stimulus was long, strong, and situated in the cervical esophagus. Acidification of the esophagus activated pharyngeal swallows and sensitized the receptors that activate the EPSR. The EPSR was blocked by local anesthesia applied to the esophageal lumen, and electrical stimulation of the recurrent laryngeal nerve caudal to the cricoid cartilage (RLNc) activated the pharyngeal swallow response. We conclude that the EPSR is activated in a probabilistic manner. The receptors mediating the EPSR are probably mucosal slowly adapting tension receptors. The sensory neural pathway includes the RLNc and superior laryngeal nerve. We hypothesize that, because the EPSR is observed in human infants and animals, but not human adults, activation of EPSR is related to the elevated position of the larynx. In this situation, the EPSR occurs rather than secondary peristalsis to prevent supraesophageal reflux when the esophageal bolus is in the proximal esophagus.

Development of infant oral feeding skills: what do we know?

The hospital discharge of premature infants in neonatal intensive care units is often delayed due to their inability to feed by mouth safely and competently. With immature physiologic functions, infants born prematurely cannot be expected to readily feed by mouth at the equivalent age of a third trimester of gestation as the majority of their term counterparts do. Consequently, it is crucial that health care professionals gain an adequate knowledge of the development of preterm infants' oral feeding skills so as to optimize their safety and competency as they transition to oral feeding. With a greater sensitivity toward their immature skills, we can offer these infants a safer and smoother transition to independent oral feeding than is currently observed. This review article is an overview of the evidence-based research undertaken over the past 2 decades on the development of very-low-birth-weight infants' oral feeding skills. The description of the different functional levels where these infants can encounter hurdles may assist caregivers in identifying a potential cause or causes for their individual patients' oral feeding difficulties.

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.

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.

Oral glucose in preterm neonates during oropharyngeal suctioning: a randomized controlled cross-over trial

To investigate whether orally applied glucose reduces pain response during oropharyngeal suctioning in preterm infants with a birth weight >1500 g, we conducted a randomized, double-blind, placebo-controlled cross-over trial on 32 preterm infants undergoing oropharyngeal suctioning while on nasal continuous positive airway pressure (CPAP). The Premature Infant Pain Profile (PIPP) score was assessed and compared in a cross-over design to investigate whether there was a significant difference in the patients' pain response. The mean PIPP score during oropharyngeal suctioning after placebo was 8.6 (KI 7.8-9.4). After glucose administration, the mean PIPP score was 8.0 (KI 7.1-8.9). Comparison of the treatment effects reached no statistic significance (p = 0.23). During the oral study drug administration during nasal CPAP, we observed 47 adverse events, but none necessitated therapeutic intervention and none was classified as serious.

CONCLUSION

In our study, late preterm infants in the first days of life did not benefit significantly from analgesia with glucose during oropharyngeal suctioning. The oral administration of glucose under nasal CPAP led to no serious adverse events.

Hiccups and amniotic fluid regulation in early pregnancy

Hiccups are an unexplained phenomenon and a subject of medical curiosity. They arise through a reflex arc with central control at the level of the medulla, and their primary physiological effect is the generation of negative intra-thoracic pressure. This paper presents the hypothesis that hiccups serve a purpose during the first half of gestation, when they are most prevalent; namely, that they promote amniotic fluid influx to the primitive gut, allowing fluid to be transferred to the foetal and then maternal vasculature. Furthermore, hiccups could be provoked by increasing amniotic fluid volume and pressure, and act in a regulatory capacity. This hypothesis could be tested by studying foetal movements in the first half of gestation, and assessing whether there is correlation with amniotic fluid flux in the developing gut. Ascertaining whether hiccups increase in frequency with increasing amniotic fluid volume would provide evidence for or against a regulatory function.

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.

Noninvasive evaluation of swallowing sound is an effective way of diagnosing feeding maturation in newborn infants

AIM

Despite extensive research, there is still controversy regarding the time at which sucking and swallowing functions mature in preterm infants. This study aimed to evaluate maturation using the noninvasive method of swallowing sound.

METHODS

We compared 52 preterm infants of between 27 and 36 weeks' gestational age with a control group of 42 healthy full-term infants. Feeding performance was based on swallowing data collected during two-minute audio recordings. The following variables were generated for each evaluation: total number of swallows, total number of rhythmic swallows, total number of resting intervals, average time between resting intervals, average time between swallows, average time between rhythmic swallows, maximum number of rhythmic swallows and volume of milk ingested. The dependency of the variables on postmenstrual age was also investigated.

RESULTS

The volume of milk ingested by the preterm infants and the maximum number of rhythmic swallows were positively correlated with postmenstrual age (PMA). The preterm infants reached the 10th percentile of the control infants at 34-35 weeks' PMA and were not significantly different from the control infants at 38-40 weeks' PMA.

CONCLUSION

Swallowing sound can be used to assess feeding maturation in preterm infants during neonatal intensive care unit follow-up.

Variation in the timing and frequency of sucking and swallowing over an entire feeding session in the infant pig Sus scrofa

Feeding is a rhythmic behavior that consists of several component cycle types. How the timing of these cycles changes over a complete feeding sequence is not well known. To test the hypothesis that cycle frequency/duration changes as a function of time spent feeding, we examined complete feeding sequences in six infant pigs, using EMG of mylohyoid and thyrohyoid as cycle markers. We measured the instantaneous frequency of sucking and of swallowing cycles in 19 sequences. Each sequence contained three qualitatively distinctive phases of sucking frequency. Phase 1 started with cycles at a very high frequency and quickly dropped to a more constant level with low variation, which characterized phase 2. Phase 3 had a steady level of frequency but was interspersed with a number of high- or low-frequency cycles. Each phase differed from the others in patterns of within-phase variation and among-phase variation. Phase 2 had the least variation, and phase 3 had the largest range of frequencies. The number of sucks per swallow also differed among phases. These patterns, which characterize normative feeding, could indicate a physiologic basis in satiation. In human infant clinical studies, where data collection is often limited, these results indicated the utility of collecting data in different phases. Finally, these results can be used as a template or pattern with which to assess clinically compromised infants.

Supraglottoplasty in Premature Infants with Laryngomalacia

Purpose

Prematurity is thought to be to be an independent risk factor for supraglottoplasty (SGP) failure. The purpose of this study was to compare the outcomes of supraglottoplasty in premature infants with congenital laryngomalacia (LM) with that of term infants.

Study Design

Case series with chart review.

Setting

Tertiary-care pediatric institution.

Methods

Analysis was performed on 325 consecutive patients undergoing SGP between 2004 and 2012. Patients older than 12 months age or with syndrome, neurologic, or cardiac comorbidities were excluded. Resolution of airway symptoms after SGP was considered successful while revision SGP and tracheostomy were considered failures. The rates of secondary airway lesions (SAL), dysphagia, and gastrostomy tube (GT) placement were also compared.

Results

A total of 176 infants (136 term, 40 preterm) were identified. SGP was successful in 92.7% term and 90% preterm infants with no significant difference ( P = .5865). Incidence of revision SGP and tracheostomy was similar among the groups. The outcomes of SGP were the same in all groups stratified by age. Incidence of SAL was significantly higher in preterm (72.5%) compared to term infants (34.6%, P = .0002). Dysphagia rates in the follow-up were higher in preterm (32.5%) versus term infants (6.6%, P < .001). The rate of GT insertion was significantly greater ( P = .003) in preterm (27.5%) than term infants (6.6%). The preoperative dysphagia, persistent dysphagia, and GT in follow-up was significantly higher when gestation age <32 weeks (25%, P = .0168).

Conclusion

Supraglottoplasty outcomes in term and preterm infants were similar irrespective of gestation age. Higher rates of dysphagia in follow-up are seen when gestation age <32 weeks.