Faculty Bibliography

In this study we undertook careful analysis of 13 quantitative physiological variables related to oropharyngeal swallowing from a sample of 42 subacute patients referred for dysphagia assessment. Each patient underwent a videofluoroscopic swallowing examination in which they swallowed up to five boluses of 22 % w/v ultrathin liquid barium suspension administered by teaspoon. Our goal was to determine whether scores on 13 kinematic or temporal parameters of interest were independently associated with the presence of penetration-aspiration in the final compiled dataset of 178 swallows. Participants were classified as aspirators based on the presence of at least one swallow that demonstrated a Penetration-Aspiration Scale score of >/=3. The parameters of interest included six kinematic parameters for capturing hyoid position, three swallow durations [laryngeal closure duration, hyoid movement duration, and upper esophageal sphincter (UES) opening duration], and four swallow intervals (laryngeal closure to UES opening, bolus dwell time in the pharynx prior to laryngeal closure, stage transition duration, and pharyngeal transit time). Mixed-model repeated-measures ANOVAs were conducted to determine the association between each parameter and aspiration status. Only 1 of the 13 parameters tested distinguished aspirators from nonaspirators: aspirators demonstrated significantly shorter UES opening duration. In addition, a trend toward reduced maximum superior position of the hyoid was seen in aspirators. Limitations and future considerations are discussed.

This study builds on previous work by Kendall, Leonard, and McKenzie, which investigated event sequence variability for 12 paired events during swallowing by healthy volunteers. They identified four event pairs that always occurred in a stereotyped order and a most common occurring overall order of events during swallowing. In the current study, we investigated overall event sequencing and the same four paired events in a sample of swallows by healthy young (under 45 years old) volunteers. Data were collected during a 16-swallow lateral videofluoroscopy protocol, which included manipulations of bolus volume, barium density, bolus viscosity, and swallow cueing. Our results agreed with previous findings that variable event sequencing is found in healthy swallowing, and, in regard to obligatory sequencing of two paired events, movement of the arytenoids toward the base of the epiglottis begins prior to upper esophageal sphincter (UES) opening and maximum hyolaryngeal approximation occurs after UES opening. However, our data failed to replicate the previous findings that there is obligatory sequencing of maximum pharyngeal constriction after maximal UES distension and the UES opens before bolus arrival at the UES. The most common observed overall event sequence reported by Kendall et al. was observed in only 4/293 swallows in our dataset. Manipulations of bolus volume, bolus viscosity, barium concentration, swallow cueing, and swallow repetitions could not completely account for the differences observed between the two studies.

Videofluoroscopy is commonly used for evaluating oropharyngeal swallowing but requires radiopaque contrast (typically barium). Prior studies suggest that some aspects of swallowing, including timing measures of oral and pharyngeal bolus transit, vary depending on barium concentration. The aim of our study was to identify timing differences in healthy swallowing between "thin" (40 % w/v concentration) and "ultrathin" (22 % w/v concentration) barium solutions. Twenty healthy adults (Ten women; mean age = 31 years) each performed a series of three noncued 5-ml swallows each of ultrathin and thin liquid barium solutions in videofluoroscopy. Timing measures were compared between barium concentrations using a mixed-model ANOVA. The measures of interest were stage transition duration, pharyngeal transit time, and duration of upper esophageal sphincter opening. Significant differences were observed in the timing measures of swallowing with respect to barium concentration. In all cases, longer durations were seen with the higher barium concentration. Barium concentration influences timing parameters in healthy swallowing, even between ultrathin and thin concentrations. Clinicians need to understand and control for the impact of different barium stimuli on swallowing physiology.

Hyoid movement in swallowing is biomechanically linked to closure of the laryngeal vestibule for airway protection and to opening of the upper esophageal sphincter. Studies suggest that the range of hyoid movement is highly variable in the healthy population. However, other aspects of hyoid movement such as velocity remain relatively unexplored. In this study, we analyze data from a sample of 20 healthy young participants (10 male) to determine whether hyoid movement distance, duration, velocity, and peak velocity vary systematically with increases in thin liquid bolus volume from 5 to 20 mL. The temporal correspondence between peak hyoid velocity and laryngeal vestibule closure was also examined. The results show that maximum hyoid position and peak velocity increase significantly for 20 mL bolus volumes compared to smaller volumes, and that the timing of peak velocity is closely linked to achieving laryngeal vestibule closure. This suggests that generating hyoid movements with increased power is a strategy for handling larger volumes.

The tongue plays a key role in the generation of pressures for transporting liquids and foods through the mouth in swallowing. Recent studies suggest that there is an age-related decline in tongue strength in healthy adults. However, whether age-related changes occur in tongue pressures generated for the purpose of swallowing remains unclear. Prior literature in this regard does not clearly explore the influence of task on apparent age-related differences in tongue pressure amplitudes. Furthermore, differences attributable to variations across individuals in strength, independent of age, have not clearly been elucidated. In this study, our goal was to clarify whether older adults have reduced tongue-palate pressures during maximum isometric, saliva swallowing, and water swallowing tasks, while controlling for individual variations in strength. Data were collected from 40 healthy younger adults (under age 40) and 38 healthy mature adults (over age 60). As a group, the mature participants had significantly lower maximum isometric pressures (MIPs). Swallowing pressures differed significantly by task, with higher pressures seen in saliva swallows than in water swallows. Age-group differences were not seen in swallowing pressures. Consideration of MIP as a covariate in the analysis of swallowing pressures revealed significant correlations between strength and swallowing pressures in the older participant group. Age-group differences were evident only when strength was considered in the model, suggesting that apparent age-related differences are, in fact, explained by differences in strength, which tends to be lower in healthy older adults. Our results show no evidence of independent differences in swallowing pressures attributable to age.

Postswallow residue is widely considered to be a sign of swallowing impairment and is assumed to pose risk for aspiration on subsequent swallows. We undertook a preliminary retrospective study to investigate the link between postswallow residue and penetration-aspiration on the immediately occurring subsequent clearing swallow (i.e., without introduction of a new bolus). Videofluoroscopy clips for 156 thin-liquid single bolus swallows by patients with neurogenic dysphagia were selected for study because they displayed multiple swallows per bolus. Residue for each subswallow (n = 407) was analyzed using the Normalized Residue Ratio Scale for the valleculae (NRRSv) and piriform sinuses. The association between residue presence at the end of a swallow and penetration-aspiration on the next swallow was examined. Postswallow residue in one or both pharyngeal spaces was significantly associated with impaired swallowing safety on the subsequent clearing swallow for the same bolus. However, when analyzed separately by residue location, only vallecular residue was significantly associated with impaired swallowing safety on the next clearing swallow. The distribution of NRRSv scores by swallowing safety demonstrated an NRRSv cut-point of 0.09, above which there was a 2.07 times greater relative risk of penetration-aspiration. Postswallow vallecular residue, measured using the NRRS, is significantly associated with penetration-aspiration on subsequent clearing swallows. A clinically meaningful cut-point of 0.09 on the NRRSv scale demarcates this risk. Further research with different bolus consistencies is needed.

The purpose of this study was to measure treatment outcomes in a group of six adults with chronic dysphagia following acquired brain injury, who each completed 24 sessions of tongue-pressure resistance training, over a total of 11-12 weeks. The treatment protocol emphasized both strength and accuracy. Biofeedback was provided using the Iowa Oral Performance Instrument. Amplitude accuracy targets were set between 20-90% of the patient's maximum isometric pressure capacity. Single subject methods were used to track changes in tongue strength (maximum isometric pressures), with functional swallowing outcomes measured using blinded ratings of a standard pre- and post-treatment videofluoroscopy protocol. Improvements were seen in post-treatment measures of tongue pressure and penetration-aspiration. No improvements were seen in pharyngeal residues, indeed worsening residue was seen in some patients.

Temporal parameters such as stage transition duration, bolus location at swallow onset, and pharyngeal transit time are often measured during videofluoroscopy, but these parameters may vary depending on assessment instructions. Specifically, "command" (cued) swallows have been observed to alter timing compared to spontaneous (noncued) situations in healthy older adults. The aim of our study was to confirm whether healthy young people show timing differences for thin liquid swallows between cued and noncued conditions. Twenty healthy young adults swallowed 10-cc boluses of ultrathin barium in videofluoroscopy. The cued condition was to hold the bolus in the mouth for 5 s before swallowing. Three noncued swallows were also recorded. In the cued condition, bolus advancement to the pyriform sinuses prior to swallow initiation was seen significantly less frequently. Stage transition durations showed a nonsignificant trend toward being shorter. Pharyngeal transit times and pharyngeal response time (a measure capturing the interval between hyoid movement onset and bolus clearance through the upper esophageal sphincter) were both significantly longer in the cued condition. Our study in healthy young adults confirms findings previously observed in older adults, namely, that swallow onset patterns and timing differ between cued and noncued conditions. In particular, bolus advancement to more distal locations in the pharynx at the time of swallow onset is seen more frequently in noncued conditions. This pattern should not be mistaken for impairment in swallow onset timing during swallowing assessment.

Post-swallow residue is considered a sign of swallowing impairment. Existing methods for capturing post-swallow residue (perceptual and quantitative) have inherent limitations. We employed several different perceptual and quantitative (ratio) methods for measuring post-swallow residue on the same 40 swallows and addressed the following questions: (1) Do perceptual and quantitative methods demonstrate good agreement? (2) What differences in precision are apparent by measurement method (one-dimensional, two-dimensional, and circumscribed area ratios)? (3) Do residue ratios agree strongly with residue area measures that are anatomically normalized? Based on the findings of this series of questions, a new method for capturing residue is proposed: the Normalized Residue Ratio Scale (NRRS). The NRRS is a continuous measurement that incorporates both the ratio of residue relative to the available pharyngeal space and the residue proportionate to the size of the individual. A demonstration of this method is presented to illustrate the added precision of the NRRS measurement in comparison to other approaches for measuring residue severity.