Abstract
Any movement performed repeatedly will be executed with inter-trial variability. Oropharyngeal swallowing is a complex sensorimotor action, and swallow-to-swallow variability can have consequences that impact swallowing safety. Our aim was to determine an appropriate method to measure swallowing pressure waveform variability. An ideal variability metric must be sensitive to known deviations in waveform amplitude, duration, and overall shape, without being biased by waveforms that have both positive and sub-atmospheric pressure profiles. Through systematic analysis of model waveforms, we found a coefficient of variability (CV) parameter on waveforms adjusted such that the overall mean was 0 to be best suited for swallowing pressure variability analysis. We then investigated pharyngeal swallowing pressure variability using high-resolution manometry data from healthy individuals to assess impacts of waveform alignment, pharyngeal region, and number of swallows investigated. The alignment that resulted in the lowest overall swallowing pressure variability was when the superior-most sensor in the upper esophageal sphincter reached half its maximum pressure. Pressures in the tongue base region of the pharynx were least variable and pressures in the hypopharynx region were most variable. Sets of 3 - 10 consecutive swallows had no overall difference in variability, but sets of 2 swallows resulted in significantly less variability than the other dataset sizes. This study identified variability in swallowing pressure waveform shape throughout the pharynx in healthy adults; we discuss implications for swallowing motor control.
Highlights
Swallowing is a critical action in daily life
Instead of developing a novel variability metric, we reviewed extant literature and adapted metrics developed for other waveform types
CVpattern was chosen to analyze pharyngeal swallowing pressures, due to its potential for direct comparison with other reports of motor variability which often use coefficient of variability (CV) as a metric. This metric may not be ideal for all applications; we recommend consideration of specific waveform permutations that are applicable to each research question prior to choosing a variability metric
Summary
Oropharyngeal swallowing requires the coordinated engagement of 31 pairs of muscles and involvement of six cranial nerves [1], with goals of preparing food and liquid into a bolus, transporting the bolus quickly through the oral cavity and pharynx into the esophagus, and protecting the airway from the bolus. Oropharyngeal swallowing has both voluntary and reflexive components. Many components of oropharyngeal swallowing are believed to be controlled by brainstem central pattern generators [3, 4], but some characteristics are cortically modulated [5,6,7,8]. Breakdown in any of the sensory or motor components of the oropharyngeal swallow can lead to inefficient and unsafe swallowing (dysphagia)
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