Purpose Thickened liquids are frequently used as an intervention for dysphagia, but gaps persist in our understanding of variations in swallowing behavior based on incremental thickening of liquids. The goal of this study was to establish reference values for measures of bolus flow and swallowing physiology in healthy adults across the continuum from thin to extremely thick liquids. Method A sex-balanced sample of 38 healthy adults underwent videofluoroscopy and swallowed 20% weight-to-volume concentration barium prepared in thin and slightly, mildly, moderately, and extremely thick consistencies using a xanthan gum thickener. Participants took comfortable sips and swallowed without a cue; sip volume was measured based on presip and postsip cup weights. A standard operating procedure (the ASPEKT method: Analysis of Swallowing Physiology: Events, Kinematics and Timing) was used to analyze videofluoroscopy recordings. Results The results clarify that, for thin liquid sips (10–14 ml), a single swallow without clearing swallows is typical and is characterized by complete laryngeal vestibule closure, complete pharyngeal constriction, and minimal postswallow residue. Aspiration was not seen, and penetration was extremely rare. Bolus position at swallow onset was variable, extending as low as the pyriform sinuses in 37% of cases. With thicker liquids, no changes in event sequencing, laryngeal vestibule closure, pharyngeal constriction, or postswallow residue were seen. The odds of penetration were significantly reduced. A longer timing interval until onset of the hyoid burst movement was seen, with an associated higher bolus position at swallow onset. Other timing measures remained unaffected by changes in bolus consistency. Conclusion The results include new reference data for swallowing in healthy adults across the range from thin to extremely thick liquids.
Many studies evaluate dysphagia in elderly patients and compare their swallowing to younger controls to assess the degree of swallowing impairment. Previous research suggests that changes should be expected in swallowing due to aging, and these changes need to be considered when performing swallowing assessments. A systematic review was conducted to elucidate the timing of swallowing in healthy. A comprehensive multiengine literature search was conducted to find articles studying swallowing in the healthy elderly, which yielded 22,852 articles of which 11 were judged to be relevant. Only articles using videofluoroscopy as an assessment method for swallowing timing were included. The articles underwent detailed review for study quality and data extraction. The eleven studies contained data for 32 different parameters, and 10 of the 11 studies compared elderly subjects to a younger group. Timing measures from the studies were compiled for analysis. In general, bolus transit times do not appear to change with age. Of note, elderly subjects tended to have a significantly delayed swallow response times and longer duration of upper esophageal sphincter opening. Results showed a large degree of variability across studies for each of the timing measures. Confidence intervals for timing in healthy older participants were computed across studies. Potential sources of variation were identified, including methodological, stimulus-related and participant-related sources. The results suggests that aging affects only a few very specific swallowing timing parameters, and many parameters appear to be unaffected by aging. Therefore, significant differences from a young reference sample should be interpreted as dysphagia rather than normal changes due to aging.
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