Aims and Scopes

The incidence of feeding and swallowing disorder has increased due to an improvement of survival rate of children with history of prematurity and life-threatening medical disorders (Arvedson, 2008; Lefton-Grief, 2008). Feeding and swallowing disorders during infancy and early childhood can lead to clinical compromises, such as malnutrition, recurrent pneumonia, chronic lung disease and stunted growth (Arvedson, 2008; Burklow et al., 1998; Newman et al., 2001).

Multiple factors contribute to swallowing disorders in pediatric populations, including history of prematurity, cerebral palsy, congenital/acquired brain injury, neuromuscular disorders, respiratory disease, congenital cardiac disease, craniofacial anomalies, airway malformations, and gastrointestinal disease (Dodrill & Gosa, 2015; Friedman & Frazier, 2000; Lefton-Grief & Arvedson 2008; Newman et al., 2001; Roden & Altman, 2013). Previous researches reported that children with medical disorders experienced various swallowing problems, including penetration, aspiration, bolus spillover while sucking, weak suck, uncoordinated suck, delayed pharyngeal response, delayed laryngeal closure, and pharyngeal residue (Arvedson et al., 1994; Dodrill & Gosa, 2015; Newman et al., 2001). In addition, researchers noted that aspiration can be related to acute pneumonia or chronic lung disease in infants and children with dysphagia (Arvedson et al., 1994; Tutor & Gosa, 2012).

Swallowing can be divided into three stages; oral, pharyngeal, and esophageal. Each stage of swallowing has its own physiology events. In adults, physiological events were investigated using temporal and biomechanical measurements based on occurrence of penetration and aspiration. For example, delayed and/or reduced airway protection are directly related to penetration and aspiration (Park et al., 2010). The physiological events during swallowing provided important clinical decision-making process in diagnosis and treatment of swallowing disorders. There is limited investigation of temporal characteristics of swallowing in pediatric populations. Swallowing disorders in pediatric populations are different from those in adults. Diagnosis and treatment should target methods to reduce risk of aspiration and occurrence of other clinical complications. However, the underlying swallowing physiology and pathophysiology in the pediatric population remains poorly understood. The videofluoroscopic swallowing examination (VFSE) is the primary instrumental examination of swallow function. The VFSE provides clinicians with information about anatomic abnormalities, coordination of oropharyngeal muscles during bolus transition, and the timing and physiology of aspiration (Arvedson et al., 1994; Logemann et al., 2000). Temporal measurement of VFSEs provides quantitative value to examine physiologic events such as bolus transition, delayed pharyngeal swallow, and laryngeal closure during swallowing. Also, the use of quantitative data can identify physiological differences between normal swallowing and abnormal swallowing (Daniels et al., 2006). Previous research reported that patients who aspirated bolus showed longer pharyngeal delay time (PDT, Kim, 2004), delayed initiation of laryngeal closure (ILC, Park et al., 2010), prolonged bolus transition (Park et al., 2013; Power et al., 2009), and longer duration of Upper Esophageal Sphincter (UES) opening (DUESO, Power et al., 2009) than the adults who had no previously reported significant swallowing disorder.

As infants and young children have different anatomical structures and an immature swallowing mechanism compared to an adult’s, temporal measures for these populations need to be modified (Petcu & Sasaki, 1991; Weckmueller et al., 2011). Currently, there is very limited research examining temporal characteristics to understand swallowing physiology in these populations. The purposes of this preliminary study were to examine temporal characteristics of swallowing in children with dysphagia and to compare temporal characteristics of children with dysphagia to those of a normal population from a previous research (Weckmueller et al., 2011). The findings of this study can provide more knowledge and understanding about swallowing physiology and pathophysiology and will allow future researchers to design appropriate management of dysphagia for infants and children.

This preliminary study investigated the temporal characteristics of oropharyngeal swallowing in children with penetration or aspiration. Also, the temporal measurements of children with penetration or aspiration were compared to those of children without penetration or aspiration. Timing measurements of swallowing using VFSE will provide valuable information about swallowing physiology and pathophysiology in infants and children. The results of this study may be a good start in the identification of specific temporal measures that can distinguish children with dysphagia from children without dysphagia.

An inter-related pattern of disorders in oral phase was observed in this study. Some infants and children showed both longer OF and longer OTT as compared to the others in the PEN/ASP group. In addition, these children showed oral residue, excessive tongue pumping, or lack of efficient sucking. Previous research reported that children with developmental disabilities have difficulty during the oral phase of swallowing, including absent oral reflexes, weak suck, and poor bolus propulsion (Arvedson 2008; Dodrill & Gosa, 2015). The PEN/ASP group had longer OF than the normal control group. Newman et al. (1991) identified that bolus transition time in oral phase increased as the number of sucks increased. The result of this study may indicate that children with dysphagia tend to have inefficient sucking. OTT was overall shorter in the PEN/ASP group than in the control group. In bottle-swallows, the valleculae contained the bolus while the subject was sucking (Newman et al., 1991). Two children in the PEN/ASP group did not collect the bolus in valleculae at all and the bolus entered the pharynx directly. In terms of temporal measurements, two children had relatively shorter OTT and longer PDT. Thus, excessively short OTT with delayed pharyngeal swallow may be related to a higher risk of aspiration.

Newman et al. (2001) reported that the most common cause of penetration and/or aspiration was delayed pharyngeal response. Henderson et al. (2016) reported that children showing arrival of the bolus at the pyriform sinus before airway closure had a higher score on penetration-aspiration scale. In addition to delayed pharyngeal swallow, impaired pharyngeal sensitivity can contribute to penetration or aspiration (Ekberg & Nylander, 1982; Friedman & Frazier, 2000). The PEN/ASP group in this study showed longer PDT and longer A to LC than the normal control group. These findings indicated that delayed hyolaryngeal excursion and delayed laryngeal closure is related to penetration and aspiration in pediatric populations. Longer A to LC in the PEN/ASP group may indicate that penetration or aspiration is due to delayed laryngeal closure. However, since A to LC included the measurement of oral filling, a future study needs to consider measurements of laryngeal closure, such as initiation of laryngeal closure and laryngeal closure duration, to examine laryngeal closure in pediatric populations.

The PEN/ASP group showed longer PTT than the normal control group. This seems to indicate that children with penetration or aspiration may have a weaker pharyngeal propulsion. Henderson et al. (2016) identified a positive correlation between weak pharyngeal constriction and longer PTT in children with dysphagia. According to Arvedson et al. (1994), children with disordered pharyngeal motility showed aspiration during VFSE. In this study, three children with aspiration were considered as outliers due to having longer PTT. They showed pharyngeal residue in valleculae and/or pyriform sinus more than the children showing only penetration.

The preliminary findings of temporal measures revealed that delayed pharyngeal swallow can be associated to potential penetration or aspiration. Position and posture changes can be a possible strategy for those who showed delayed pharyngeal swallow. For the younger children, postural change during feeding may be good strategy. Leaning toward stronger side will help the children transport the bolus safely in the pharynx. Larnert & Ekberg (1995) identified that chin-tuck with 30-degree reclined position reduced the occurrence of aspiration in children with cerebral palsy. A widened valleculae by chin-tuck held the bolus for a period of time so that the time for initiation of pharyngeal swallow increased. Other swallowing maneuvers, including thermal stimulation, supraglottic and effortful swallow, may help older children facilitate the swallow response and laryngeal closure (Lefton-Grief, 2008; O’Donoghue & Bagnall, 1999).

This study had several limitations, including the small number of subjects, which required a descriptive analysis which provide lacking information to compare temporal measurements between the groups. The range of subject’s age are relatively big. This data may not represent the population of pediatric dysphagia population but will be a good foundation for the future study. Additionally, the published data were used for the normal group, resulting in a limited number of temporal measurements available for analysis. The author contacted the previous researchers to obtain normal data of temporal measurements, but they could not share them with other institute. Thus, future studies should recruit more subjects to conduct inferential statistical analysis. Also, additional research regarding temporal measurements that examine laryngeal closure and function of the upper esophageal sphincter during oropharyngeal swallowing would provide clinicians with more information to understand the swallowing function in pediatric populations.

This study is part of a long-term project, which will collect more normative data about swallowing physiology in pediatric populations. Normative data could serve as a reference to monitor changes in swallowing function of pediatric populations over time. It is important to note that a swallowing evaluation needs to identify types and physiological causes of swallowing disorders. It is crucial for valid and reliable temporal measures to be developed so that normal swallowing is more easily distinguished from abnormal swallowing. Additionally, these temporal measure developments will assist with determining the relationship between swallowing physiology events and aspiration. Overall, the valid and reliable temporal measures determined by current and future studies will provide clinicians with evidence to facilitate appropriate intervention.