Upper esophageal sphincter mechanical states analysis: a novel methodology to describe UES relaxation and opening

Abstract

The swallowing muscles that influence upper esophageal sphincter (UES) opening are centrally controlled and modulated by sensory information. Activation of neural inputs to these muscles, the intrinsic cricopharyngeus muscle and extrinsic suprahyoid muscles, results in their contraction or relaxation, which changes the diameter of the lumen, alters the intraluminal pressure and ultimately inhibits or promotes flow of content. This relationship that exists between the changes in diameter and concurrent changes in intraluminal pressure has been used previously to calculate the “mechanical states” of the muscle; that is when the muscles are passively or actively, relaxing or contracting. Diseases that alter the neural pathways to these muscles can result in weakening the muscle contractility and/or decreasing the muscle compliance, all of which can cause dysphagia. Detecting these changes in the mechanical state of the muscle is difficult and as the current interpretation of UES motility is based largely upon pressure measurement (manometry), subtle changes in the muscle function during swallow can be missed. We hypothesized that quantification of mechanical states of the UES and the pressure-diameter properties that define them, would allow objective characterization of the mechanisms that govern the timing and extent of UES opening during swallowing. To achieve this we initially analyzed swallows captured by simultaneous videofluoroscopy and UES pressure with impedance recording. From these data we demonstrated that intraluminal impedance measurements could be used to determine changes in the internal diameter of the lumen when compared to videofluoroscopy. Then using a database of pressure-impedance studies, recorded from young and aged healthy controls and patients with motor neuron disease, we calculated the UES mechanical states in relation to a standardized swallowed bolus volume, normal aging and dysphagia pathology. Our results indicated that eight different mechanical states were almost always seen during healthy swallowing and some of these calculated changes in muscle function were consistent with the known neurally dependent phasic discharge patterns of cricopharyngeus muscle activity during swallowing. Clearly defined changes in the mechanical states were observed in motor neuron disease when compared to age matched healthy controls. Our data indicate that mechanical state predictions were simple to apply and revealed patterns consistent with the known neural inputs activating the different muscles during swallowing.

Pressure-Flow Analysis for the Assessment of Pediatric Oropharyngeal Dysphagia

“…Patients with clinical signs of OPD and a poor functional oral intake score (FOIS score 1-3) showed residual UES pressures and significantly higher UES impedance recordings during bolus flow. These markers indicate restricted UES opening (23,24).…”

Modulation of Upper Esophageal Sphincter (UES) Relaxation and Opening During Volume Swallowing

“…We overcame this limitation during interpretation of UES data by constantly tracking the highest pressure within the sphincter zone, as described by Ghosh et al (Figure 1C) [23]. CP-EMG is challenging to record, and our study showed that UES relaxation closely correlated with CP deactivation and can substitute CP recording during recording of UES neuromuscular mechanical states [24,25]. Comparatively, SM-EMG is easy to record via surface electrodes, and we would continue to advocate for the use of SM-EMG in better understanding oropharyngeal dysphagia across bolus volumes and in relation to the efficacy of swallowing maneuvers during studies of UES opening.…”

“…To date, we have been unable to record intramuscular EMG during radiology, due to interference from the fluoroscopy unit, rendering the EMG recording uninterpretable. Admittance criteria for bolus presence based on radiological UES opening had previously been described [25] and thus the use of impedance manometry allowed us to substitute admittance based sphincter opening.…”

Supraesophageal Reflux Disease: Solving a Riddle Wrapped in a Mystery Inside an Enigma

“…19 Application of PFA in patients with pharyngeal dysfunction identifies biomechanical factors that determine the success or failure of the swallow and defines the risk of aspiration. 19,20 This includes not only UES relaxation, but also UES opening and the efficacy of pharyngeal clearance. 20 Adapting this approach, UES responses to esophageal infusion could be quantified in terms of "flow permissive characteristics" to detect factors that determine the risk of supra-esophageal reflux.…”

“…19,20 This includes not only UES relaxation, but also UES opening and the efficacy of pharyngeal clearance. 20 Adapting this approach, UES responses to esophageal infusion could be quantified in terms of "flow permissive characteristics" to detect factors that determine the risk of supra-esophageal reflux.…”