Pediatric Swallowing, Laryngopharyngeal and Gastroesophageal Reflux Disease, Eosinophilic Esophagitis, and Aspiration

Normal Swallowing Physiology

The swallowing process involves interactions of multiple neurologically based systems, making this process one of the most complex functions in all living beings. It includes several anatomic structures with both voluntary and involuntary neurologic components. The initiation of the pharyngeal swallow requires simultaneous inhibition of respiration. The central nervous system (CNS) coordinates sensory and motor components, consisting of afferent sensory input and voluntary and involuntary motor responses from the brainstem and enteric nervous systems. Hormonal factors appear to have a critical role, which is not well understood to date.

Neurophysiology of swallowing involves control by the pattern generators in the brainstem that are modulated by the cerebral cortex, which integrates sensory input. The swallowing process begins under voluntary neural control in response to food/liquid (or saliva) in the oral cavity. Infants, young children, and older children with neurologically based disabilities are typically fed by caregivers. Children initiate bolus formation via lip, tongue, and jaw action. Bolus formation is minimal for infants, limited to latching onto the nipple. When infants begin to take smooth food by spoon at about 6 months of age and gradually advance to thicker and lumpy foods, bolus formation becomes more distinct and may last for several seconds. Oral transit begins with posterior tongue propulsion and ends when the pharyngeal swallow is initiated. During bolus formation and oral transit, sensory input and feedback are critical to normal swallowing. These sensors include mechanoreceptors (touch, pressure); pain receptors; proprioceptive receptors (shape, location); chemical receptors; and special receptors for taste, smell, and temperature. Mechanoreceptors in the tongue, teeth, and soft and hard palate aid in modulating muscles of mastication through brainstem integrative pathways.

Whereas initiation of the pharyngeal swallow is under voluntary neural control, completion of the pharyngeal phase is under involuntary neural control. Potential for aspiration is high if there is reduced muscular strength or any delay in retraction of the tongue base and/or contraction of pharyngeal constrictors. In the normal swallow, airway protection occurs at multiple levels, through laryngeal closure achieved by adduction of true and false vocal folds, pharyngeal muscle contractions, elevation/retraction of the soft palate, and epiglottic retroflexion. Some studies have shown that false vocal folds are closed during swallowing, whereas others have found that false vocal folds generally remain open. Cessation of breathing with laryngeal closure preceding bolus propulsion has been confirmed in infants and children. ^, The muscular upper esophageal sphincter (UES) does not simply relax; its opening occurs through precise coordination between bolus transport and anterior superior elevation of the larynx that assists in airway protection. Notably, occasional laryngeal penetration, which appears as transient barium spillover into the laryngeal vestibule above the level of the true vocal folds, may occur in healthy individuals. Aspiration is defined by progress of material below the true vocal folds into the trachea.

These events occur rapidly without interruption of the posterior bolus movement, and the pharynx is completely cleared, leaving no residue in the pharyngeal recesses after completion of the swallow. The epiglottis diverts food laterally into the pyriform sinuses as one of the pharyngeal swallowing mechanisms for airway protection. However, it must be noted that the epiglottis is not a critical structure in all instances for airway protection during swallowing ; functional safe swallowing is reported with an absent epiglottis. [CR] Esophageal transit occurs as peristaltic waves carry the bolus into the stomach, primarily under involuntary neural control mediated by the vagus nerve.

Swallowing maturation evolves from the primitive sucking and swallowing patterns seen during the first few months of life into mature functions of chewing, biting, and bolus formation necessary for the safe and adequate delivery of nutrients in older children and adults. Well-described changes in the anatomic relationships of the oral cavity, pharynx, and larynx occur through the first few years of life. In addition, the maturation process of oral feeding may be influenced by neurodevelopmental, cognitive, and sensory inputs. The functions of breathing and swallowing are interrelated and must be considered together.

Competent deglutition/swallowing is fundamental to survival. A stable airway is basic to oral feeding. Thus breakdowns in the systems underlying breathing and/or eating result in dysphagia. Clinical and instrumental evaluations of children with feeding and swallowing problems are useful tools for evaluation. Management decisions depend on an adequate evaluation that takes into account all aspects of neurologic, pulmonary, gastrointestinal (GI), nutritional, and oral sensorimotor functions. In addition, family relationships and cultural differences are primary factors that must be prioritized when professionals make decisions.

Clinical Feeding Evaluation of Infants and Young Children

Arvedson proposed purposeful key questions for physicians and other professionals to ask parents of infants and children with suspected feeding and swallowing difficulties. Affirmative answers are considered “red flags” that warrant a clinical feeding evaluation to facilitate early intervention. These questions cover four problem areas associated with feeding difficulties: prolonged mealtime duration, mealtime stress, concerns regarding growth, and respiratory conditions. Coughing with feeding, a requirement for multiple swallows, and/or recurrent pneumonias could indicate dysphagia with airway concerns. Prolonged feeding of a child, frequent retching or vomiting, poor weight gain, or oral sensorimotor impairment can lead to malnutrition in a child.

Empirical research is needed to determine which questions may be most discriminative in detecting feeding/swallowing disorders and to determine their applicability across the spectrum of disorders. Thus far, a retrospective study of children with cerebral palsy (CP) has evaluated the relationship between commonly cited feeding/swallowing risk factors, including the red flags and outcomes and undernutrition. The investigators concluded that the red flags appear to be feasible screening questions for parents of children with CP, but that there is a need to add an “eating/drinking difficulty” item.

Parents’ concerns are most frequently the basis for referrals. ^, A clinical feeding evaluation may be carried out at the bedside or in any other setting. Components include a history and physical examination; formulation of hypotheses regarding the nature and severity of the feeding problem/dysphagia; establishment of baselines with observation of feeding with oral sensation and breathing; introduction of therapeutic modifications such as posture/position/texture; investigation of “safe” feeding options for the child; determination of the need for additional specialized examinations or instrumental swallow evaluation, including the child’s readiness; and the development of a plan for follow-up testing, observation, and/or intervention.

Instrumental Evaluation of Swallowing

An instrumental swallow evaluation is needed to define pharyngeal physiology, which can only be inferred from a clinical feeding/swallowing evaluation. The video fluoroscopic swallow study (VFSS) is the primary instrumental examination that provides dynamic imaging of bolus flow through oral, pharyngeal, and esophageal anatomic regions of the upper aerodigestive tract in real time. Introduced by Logemann in 1983, the purposes of the VFSS are to study the anatomy and physiology of the oral preparatory, oral, pharyngeal, and cervical esophageal phases of swallowing. [CR] The VFSS is not intended simply to identify presence or absence of aspiration, nor is it a “pass” or “fail” test. If aspiration does occur, the interpretation provides insight into the reason or reasons for aspiration, which helps guide appropriate intervention. Use of VFSS in children has increased over the last 2 decades because of a greater number of children with swallowing problems, likely related to improved survival rates of preterm infants and infants undergoing cardiac, airway, and GI tract surgical procedures. Children must be cooperative if the clinician is to obtain valid and reliable information. Few instruments exist for the reproducible quantification of swallow physiology, and standardization is needed for reporting findings and interpreting results, particularly for infants and young children.

Important considerations in decision making (details beyond the scope of this chapter) include radiation exposure, changes in technology, the generalizability of judgments made by observing images from a small number of swallows in a short period of time (usually 1 to 3 minutes), and the concordance between barium contrast and the foods/liquids typically found in the child’s diet. Decisions regarding oral versus tube feeding to meet nutrition/hydration needs, alterations of textures/consistencies of food and liquid, postural and position adjustments, and sensorimotor intervention or other therapeutic maneuvers should not be made strictly based on findings in an instrumental swallowing examination; the underlying medical and developmental factors, nutrition status, and parent–child interactions must be considered. The findings on VFSS, albeit important, provide information that must be incorporated into the “whole” person.

Fiberoptic endoscopic evaluation of swallowing (FEES) provides visualization of swallow events that occur immediately before and immediately after the initiation of the pharyngeal swallow. There is no information regarding manipulation and movement of the bolus in the oral cavity, nor below the level of the true vocal folds; however, because vocal folds are abducted as the pharyngeal swallow is completed, aspirated material may at times be seen in the trachea. FEES is best carried out by an otolaryngologist and speech-language pathologist working as a team. Anatomic structures are visualized as the endoscope is passed transnasally. A “white out” occurs as the epiglottis tilts on pharyngeal swallow initiation. Visualization of any residue can be noted in the valleculae, pyriform sinuses, posterior pharyngeal wall, and laryngeal vestibule as soon as the epiglottis returns to rest position. If the patient has an upper airway abnormality such as vocal cord immobility, FEES evaluates the patient’s ability to obtain glottic closure with various consistencies and determines whether penetration or gross aspiration occurs. One disadvantage of FEES is the inability to visualize the entire dynamic swallow sequence. Advantages of FEES include no radiation exposure, flexible positioning, possibility of frequent repetition, and feasibility of performing in any setting, including the neonatal intensive care unit (NICU) for breast- and bottle-fed infants. ^, There is limited evidence correlating FEES results to clinical diagnoses and feeding outcomes. Sitton and colleagues compared clinical diagnoses and initial FEES findings to follow-up feeding status in a retrospective review. Long-term feeding status was not significantly associated with initial FEES findings, although most children showed improvement.

VFSS and FEES may delineate characteristics that correlate with a diagnosis of dysphagia. It must be emphasized that these relatively brief examinations when children are not in a typical feeding situation may fail to detect aspiration. In addition, intermittent aspiration with feeding events may not be captured during these procedures. Children with dysphagia caused by neurologic disorders are more likely to aspirate intermittently or without cough or other identifiable response, which contributes to management dilemmas. Thus findings must always be interpreted with caution.

Management of Infants and Children With Swallowing/Feeding Problems

The primary goals of intervention are to facilitate adequate nutrition/hydration in ways that do not compromise the stability of the airway. The International Classification of Function (ICF), Disability, and Health Model from the World Health Organization (WHO) provides a framework for classification and function that has been applied to feeding and swallowing in children. This framework provides a holistic approach to both assessment and management; the focus is on function with consideration of possible interfering factors rather than on impairments. The concepts in this framework are applicable to all ages of children and types and severity of dysphagia while respecting cultural and ethnic variables.

Management decisions consider nutritional status, medical and surgical stability, position/posture needs, oral sensorimotor facilitation, oropharyngeal swallow safety, and behavioral factors. Neurodevelopmental sensorimotor principles of learning and experience-dependent neural plasticity provide a foundation for direct therapeutic intervention. Peak or sensitive periods of neural plasticity appear to coincide with rapid brain growth early in life, even though potential neural plasticity continues throughout the life span. Interference may occur when response to one experience can inhibit acquisition of other responses. For example, maladaptive behaviors may occur when oral sensorimotor intervention is carried out with approaches that are not directly related to functional eating or drinking. These approaches have limited evidence to support their efficacy and include but are not limited to stretching and stroking, passive range of motion, vibratory oral tools, and neuromuscular electrical stimulation (NMES). Although NMES has gained popularity, an impact on outcomes has not been demonstrated. Recent literature reviews stress the need for research in both process and outcomes.