The early impact of feeding on infant breathing-swallowing coordination

Evidence of intermediate reticular formation involvement in swallow pattern generation, recorded optically in the neonate rat sagittally sectioned hindbrain

Swallow is a primitive behavior regulated by medullary networks, responsible for movement of food/liquid from the oral cavity to the esophagus. To investigate how functionally heterogeneous networks along the medullary intermediate reticular formation (IRt) and ventral respiratory column (VRC) control swallow, we electrically stimulated the nucleus tractus solitarius to induce fictive swallow between inspiratory bursts, with concurrent optical recordings using a synthetic Ca²⁺ indicator in the neonatal sagittally sectioned rat hindbrain (SSRH) preparation. Simultaneous recordings from hypoglossal nerve rootlet (XIIn) and ventral cervical spinal root C1-C2 enabled identification of the system-level correlates of 1) swallow (identified as activation of the XIIn but not the cervical root) and 2) Breuer-Hering expiratory reflex (BHE; lengthened expiration in response to stimuli during expiration). Optical recording revealed reconfiguration of respiration-modulated networks in the ventrolateral medulla during swallow and the BHE reflex. Recordings identified novel spatially compact networks in the IRt near the facial nucleus (VIIn) that were active during fictive swallow, suggesting that the swallow network is not restricted to the caudal medulla. These findings also establish the utility of using this in vitro preparation to investigate how functionally heterogeneous medullary networks interact and reconfigure to enable a repertoire of orofacial behaviors.NEW & NOTEWORTHY For the first time, medullary networks that control breathing and swallow are recorded optically. Episodic swallows are induced via electrical stimulation along the dorsal medulla, in and near the NTS, during spontaneously occurring fictive respiration. These findings establish that networks regulating both orofacial behaviors and breathing are accessible for optical recording at the surface of the sagittally sectioned rodent hindbrain preparation.

Pathophysiology of aspiration in a unilateral SLN lesion model using quantitative analysis of VFSS

OBJECTIVE

The purpose of this study was to elucidate the pathophysiology of aspiration in previously studied female infant piglets after a unilateral superior laryngeal nerve (uSLN) lesion.

METHODS

Videofluoroscopic swallow studies (VFSS) were acquired from 15 female piglets ages 2-3 weeks (9 with uSLN lesion and 6 controls). VFSS were analyzed at 30 frames/second sampling rate. Quantitative measures were conducted and compared between groups using published methodologies for VFSS assessment in adult and infant humans. Measures included the: 1) number of lingual-palatal contacts (LPC) (i.e. pre-swallow), 2) total pharyngeal transit time (TPT), 3) offset of swallow (offP), as well as onset of: 4) pharyngeal stage (onP), 5) pharyngoesophageal segment opening (oPES), 6) maximum PES opening (maxPES), 7) airway closure onset (oAC), and 8) maximum airway closure (maxAC). Measures 5-7 were determined relative to onP. Bolus residue was rated by severity (0 (none) to 3 (severe)). A gamma regression was used to compare continuous measures between lesioned and control groups.

RESULTS

The number of LPC (p = .006), TPT (p = .023) and timing of maxAC (p = .041) were significantly greater in the uSLN lesion than the control group.

CONCLUSIONS

Outcomes of this study replicated prior published findings and elucidated that piglets with right uSLN lesions exhibited delayed maxAC. Noteworthy was the use of clinically relevant quantitative videofluoroscopic measures in piglets for comparison to future studies in human pediatric populations.

Fiberoptic Endoscopic Evaluation of Swallowing in Infants and Children: Protocol, Safety, and Clinical Efficacy: 25 Years of Experience

BACKGROUND

The application of fiberoptic endoscopic evaluation of swallowing (FEES) in the pediatric dysphagia protocol requires specialized knowledge of pediatric conditions that result in dysphagia, recognition of normal and abnormal laryngopharyngeal anatomy and function across ages, and the ability to identify maturational changes in anatomy and function of the aerodigestive tract that pertain to airway protection and swallowing function.

METHODS

Over the past 25 years, we have performed over 7,000 collaborative Otolaryngology and Speech-Language Pathology FEES examinations in patients ranging from 2 days of age to young adults. During this time period, we have monitored the safety of the procedure, explored the feasibility and utility of FEES across conditions, compared and contrasted FEES to the videofluoroscopic evaluation of swallowing (VFSS), and developed specific pediatric FEES protocols with operational definitions for identification and interpretation of swallowing parameters.

RESULTS

FEES has proved to be a safe procedure in patients across ages. There have been no significant adverse events. FEES is comparable to the VFSS in the assessment of events before and after the swallow. It provides unique information regarding laryngopharyngeal anatomy and function, airway protection integrity, sensory threshold, and secretion management ability, as well as pharyngeal swallowing dynamics and the efficacy of compensatory swallowing strategies.

CONCLUSIONS

There are specific indications and contraindications for pediatric FEES, and unique components that characterize the pediatric FEES protocols across ages and conditions. FEES procedures performed jointly by an Otolaryngologist and Speech-Language pathologist offer a team approach to interpretation and management recommendations.

Respiratory-Swallow Pattern Following Total Laryngectomy

The goal of this study was to further characterize respiratory patterns in total laryngectomees with attention to respiratory-swallow pattern as it relates to presence/absence of tracheoesophageal puncture (TEP) and bolus consistency. It was hypothesized that participants with TEP would exhibit respiratory-swallow patterns that were significantly different than those without TEP and that bolus consistency (thin or solid) would modulate respiratory-swallow pattern. Data were collected from 12 adults (8 male), aged 46-67 years (mean 57) status post total laryngectomy (1-30 years; average 6 years). Those actively receiving chemoradiation, with history of esophageal cancer, with neurologic disease, with history of lung cancer, with known or suspected recurrence of head and neck cancer (HNC), or with severe cognitive deficits were excluded. Laryngectomy participants were asked to swallow three sips of water and three bites of graham cracker. Submental surface EMG activity was used to detect swallows and a custom stoma mask in line with a pneumotachograph measured airflow during the swallows. Non-parametric Mann-Whitney test for differences was used to detect significance for our dependent variables, TEP or bolus consistency and independent variables, respiratory-swallow pattern. Laryngectomee's showed preference for swallow during inspiration which is inconsistent with the expiratory pattern preference found in healthy adults with intact larynges by McFarland et al. (Respir Physiol Neurobiol 234:89-96, 2016) but consistent with the pattern preference for inspiration (or non-dominant respiratory-swallow phase pattern) found in the HNC population at-large by Brodsky et al. (J Appl Physiol 112(10):1698-1705, 2012). No significant difference was found in swallow pattern with regards to presence/absence of TEP or bolus consistency.

Descent of the human larynx: An unrecognized factor in airway distress in babies with cleft palate?

The intranarial epiglottis, a feature of all newborn mammals, allows suckling and breathing to continue almost simultaneously by separating an oral food stream from a nasal airstream. In contrast to other mammals, the human larynx descends in the neck between birth and six months, extending the distance between the caudal aspect of the soft palate and the cephalic tip of the epiglottis. The mechanism of airway protection changes from a pattern in which an upright epiglottis is grasped by an intact palatopharyngeal sphincter to one in which the epiglottis folds down over the laryngeal aditus and the adducted vocal folds. The comparative anatomy and anthropological literature describing laryngeal descent was reviewed. A series of MRI images were used to illustrate the normal descent of the human larynx, which take place in infants in the first six months of life. Based on this information, we hypothesize that a cleft palate, by interrupting the sphincter function of palatopharyngeus on a high neonatal epiglottis, precipitates a need for premature and rapid maturation of the neonate's airway protection pattern, particularly during feeding. This may explain why, even in the absence of Robin sequence, some babies with cleft palates suffer respiratory distress during feeding.

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.

Embryonic hindbrain patterning genes delineate distinct cardio-respiratory and metabolic homeostatic populations in the adult

Previous studies based on mouse genetic mutations suggest that proper partitioning of the hindbrain into transient, genetically-defined segments called rhombomeres is required for normal respiratory development and function in neonates. Less clear is what role these genes and the neurons they define play in adult respiratory circuit organization. Several Cre drivers are used to access and study developmental rhombomeric domains (Eng1^Cre, HoxA2-Cre, Egr2^Cre, HoxB1^Cre, and HoxA4-Cre) in the adult. However, these drivers show cumulative activity beyond the brainstem while being used in intersectional genetic experiments to map central respiratory circuitry. We crossed these drivers to conditional DREADD mouse lines to further characterize the functional contributions of Cre defined populations. In the adult, we show that acute DREADD inhibition of targeted populations results in a variety of not only respiratory phenotypes but also metabolic and temperature changes that likely play a significant role in the observed respiratory alterations. DREADD mediated excitation of targeted domains all resulted in death, with unique differences in the patterns of cardio-respiratory failure. These data add to a growing body of work aimed at understanding the role of early embryonic patterning genes in organizing adult respiratory homeostatic networks that may be perturbed in congenital pathophysiologies.

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.

The Pediatric Lung and Aspiration

This article offers an over view of lung development, physiology, and evaluation of lung damage due to aspiration. Considerations specific to pediatric patients are discussed.

Coordination of respiration and swallowing: functional pattern and relevance of vocal folds closure

CONTEXT: Breathing and swallowing coordination, despite the expressive number of study, remain as theme deserving further research. OBJECTIVE: To identify a coordination pattern between swallowing and the natural breathing pause that occur in association with it (swallowing apnea) and also the relevance of the vocal folds closure in this process. METHODS: Sixty-six adults, male and female, including normal health people, post-laryngectomy individuals and patients with digestive complaints without dysphagia were analyzed. The respiratory air flux interruptions produced by wet requested swallows and dry, requested and spontaneous swallows, were registered using thermo and piezoelectric receptors coupled to synectics medical manometry equipment, using Polygram upper 4.21 software. The results were analyzed with the Chi-square (3×2) and (2×2) nonparametric independency test with P = 0.05. RESULTS: Swallowing apnea is a preventive breathing stop that start just before and stay present during all deglutition pharyngeal phase. It is a well coordinated phenomena that occur as pattern in association with low elastic resistance of the lung, on the expiratory final phase until inspiration initial phase. This breathing stoppage it is usually followed by a short expiraton preceding a new breathing cycle. The swallow apnea and vocal folds closure are both independents mechanisms. CONCLUSION: It is possible to suppose that in the subconscious condition, swallowing apnea is integrated under coordination of the same control mechanism that also involves the elastic resistance of the lung.

Oropharyngeal dysphagia in patients with chronic obstructive pulmonary disease: a systematic review

BACKGROUND: oropharyngeal dysphagia in patients with chronic obstructive pulmonary disease. PURPOSE: patients with Chronic Obstructive Pulmonary Disease (COPD) can be vulnerable to respiratory incompetence that may lead to swallowing impairment. A systematic review was conducted to investigate the relationship between Chronic Obstructive Pulmonary Disease and oropharyngeal dysphagia. Forty-seven articles were retrieved relating to Chronic Obstructive Pulmonary Disease and dysphagia. Each article was graded using evidence-based methodology. Only 7 articles out of the 47 addressed oropharyngeal swallowing disorders in patients with Chronic Obstructive Pulmonary Disease. This review found few studies that documented the relationship between oropharyngeal swallowing disorders and Chronic Obstructive Pulmonary Disease. There were no randomized control trials. CONCLUSION: although the evidence is not strong, it appears that patients with Chronic Obstructive Pulmonary Disease are prone to oropharyngeal dysphagia during exacerbations. Future studies are needed to document the prevalence of oropharyngeal dysphagia in homogeneous groups of patients with Chronic Obstructive Pulmonary Disease, and to assess the relationship between respiration and swallowing using simultaneous measures of swallowing biomechanics and respiratory function. These investigations will lead to a better understanding of the characteristics and risk factors of developing oropharyngeal dypshagia in patients with Chronic Obstructive Pulmonary Disease.

Central pattern generation involved in oral and respiratory control for feeding in the term infant

PURPOSE OF REVIEW

Drinking and eating are essential skills for survival and benefit from the coordination of several pattern generating networks and their musculoskeletal effectors to achieve safe swallows. Oralpharyngoesophageal motility develops during infancy and early childhood, and is influenced by various factors, including neuromuscular maturation, dietary and postural habits, arousal state, ongoing illnesses, congenital anomalies, and the effects of medical or surgical interventions. Gastroesophageal reflux is frequent in neonates and infants, and its role in neonatal morbidity including dysphagia, chronic lung disease, or apparent life-threatening events is not well understood. This review highlights recent studies aimed at understanding the development of oral feeding skills, and cross-system interactions among the brainstem, spinal, and cerebral networks involved in feeding.

RECENT FINDINGS

Functional linkages between suck-swallow and swallow-respiration manifest transitional forms during late gestation through the first year of life, which can be delayed or modified by sensory experience or disease processes, or both. Relevant central pattern generator (CPG) networks and their neuromuscular targets attain functional status at different rates, which ultimately influences cross-system CPG interactions. Entrainment of trigeminal primary afferents accelerates pattern genesis for the suck CPG and transition-to-oral feed in the RDS preterm infant.

SUMMARY

The genesis of within-system CPG control for rate and amplitude scaling matures differentially for suck, mastication, swallow, and respiration. Cross-system interactions among these CPGs represent targets of opportunity for new interventions, which optimize experience-dependent mechanisms to promote safe swallows among newborn and pediatric patients.

Ultrasound imaging of infant swallowing during breast-feeding

Coordination of infants' suck-swallow-breathing patterns is integral to safe and efficient feeding. However, assessment of these patterns is difficult and often invasive, particularly in breast-fed infants less than 4 months of age. The aims of this study were to develop an ultrasound approach to visualize swallowing in term breast-feeding infants and to determine the accuracy of ultrasound imaging of swallowing compared to respiratory inductive plethysmography (RIP). On ultrasound, the breast milk bolus was observed as a predominantly echogenic area moving inferiorly. Of the 388 swallows detected with ultrasound, 379 correlated with the swallow apneas detected by RIP (R(2) = 0.98). The mean duration of the swallow was 0.63 +/- 0.06 s. Ultrasound imaging is a noninvasive accurate method for detection of swallowing by visualization of movement of the milk bolus through the pharyngeal area of a breast-feeding infant. These techniques may potentially provide useful information for infants experiencing breast-feeding difficulties.

Coordination of Mastication, Swallowing and Breathing

The pathways for air and food cross in the pharynx. In breathing, air may flow through either the nose or the mouth, it always flows through the pharynx. During swallowing, the pharynx changes from an airway to a food channel. The pharynx is isolated from the nasal cavity and lower airway by velopharyngeal and laryngeal closure during the pharyngeal swallow. During mastication, the food bolus accumulates in the pharynx prior to swallow initiation. The structures in the oral cavity, pharynx and larynx serve multiple functions in breathing, speaking, mastication and swallowing. Thus, the fine temporal coordination of feeding among breathing, mastication and swallowing is essential to provide proper food nutrition and to prevent pulmonary aspiration. This review paper will review the temporo-spatial coordination of the movements of oral, pharyngeal, and laryngeal structures during mastication and swallowing, and temporal coordination between breathing, mastication, and swallowing.

Arousal has no effect on non-nutritive breathing-swallowing coordination during the first year of human life

Although the brainstem plays an important role in breathing-swallowing coordination (BSC), the role of suprabulbar structures is ill defined. Given the known decrease in global cerebral activity during sleep, the sleep-wake paradigm was used to elucidate suprabulbar influences. Non-nutritive BSC of 10 healthy human infants was monitored longitudinally during wakefulness and sleep from birth to 1 year of age. Time-locked recordings of submental muscle activity, nasal airflow, and thyroid acoustics enabled the categorization of swallows depending on the preceding and following respiratory phase. In contrast to the change in the overall pattern of BSC with age, and despite well-known marked postnatal cortical development over this time, no arousal-related differences were seen during the first year of life. This most likely reflects complete brainstem control of non-nutritive BSC in infants.