The upper esophageal sphincter (UES) plays a unique role in the process of swallowing. While most structures are relaxed at rest, the UES functions in a contracted state as a barrier between the pharynx and the esophagus. The UES relaxes and is opened during swallowing to allow bolus passage through a series of well-coordinated events. This research programme pursues an interest in the UES through two arms of research, one to contribute to current knowledge about deglutitive UES function; another to investigate UES rehabilitation options.

In the first arm of this research programme, dynamic pressure changes in the UES and closely associated regions – the pharynx and the esophagus – were investigated with manometry. Study 1 first addressed a methodological knowledge gap by investigating how the use of topical nasal anaesthetic (TNA) affected swallowing and comfort during high-resolution impedance manometry (HRIM). Twenty healthy participants underwent two randomised conditions of HRIM using the ManoScanTM ESO Z 4.2 mm catheter: with TNA (1 ml of 2% viscous lidocaine hydrochloride mixed with 1 ml of lubricant) and placebo (2 ml of lubricant). Studies were one week apart, and participants were blinded to condition. Participants performed saliva, saline (5 ml) and bread (2 cm x 2 cm x 2 cm) swallows while reclined 45 degrees (esophageal HRIM), and again while seated upright (pharyngeal HRIM). The Swallow GatewayTM analysis system (Omari, 2018a) was used to process HRIM data. Results indicated that TNA did not improve comfort, but it also did not significantly affect swallowing behaviour. There was, however, a practice effect regardless of TNA use with improved tolerability of the 4.2 mm catheter and likely more natural swallowing behaviour during the second session of HRIM.

Study 2 investigated if gastroesophageal reflux disease (GERD) or achalasia and associated esophageal changes alter pressure dynamics in the UES and pharynx. Thirty patients with GERD and 28 age- and gender-matched healthy volunteers underwent a session of HRIM. The HRIM protocol and data extraction methods were as per Study 1. Parameters from the pharynx and esophagus were correlated directly to the UES separately. Three patients with achalasia were recruited who underwent the same HRIM protocol, with their data analysed as a case series. In patients with GERD, there was no association between esophageal and UES function. However, pharyngeal contractile vigour increased with reduced UES relaxation. This likely indicates a pharyngeal maladaptive response to overcome UES obstruction to aid bolus passage during swallowing. If the maladaptive response persists over time, there is the possibility of development of pharyngeal pathology in relation to UES abnormalities in patients with GERD. For patients with achalasia, all presented with Type II achalasia according to the Chicago Classification version 3.0. As expected, impaired UES relaxation was observed. These results provide limited evidence for changes in the esophagus related with upstream changes in the UES, but not consistently in the pharynx, during swallowing.

The second arm of the research programme investigated the capacity for behavioural modulation of the UES. Study 3 first investigated normal variation in repeated measures of UES function from high-resolution manometry (HRM) and videofluoroscopic swallowing studies (VFSS). HRM data were collected from 20 healthy participants across three sessions. At each session, resting and intra-swallow nadir relaxation pressures and relaxation durations were recorded using a small diameter ManoScanTM ESO 2.75 mm catheter from the region of the UES during five trials each of saliva, 5 ml water and 5 ml puree swallows. Due to malfunctioning sensors with increased use in the HRM catheter, data from only 14 participants remained viable for extraction after recording. UES measures from VFSS were extracted from retrospective studies to minimise the need for unnecessary exposure of healthy volunteers to radiation. However, across session data were not available and within session data were from 20 healthy participants ingesting five 5 ml thin liquid barium swallows. UES opening width and duration from the lateral view across five trials were measured. Greater variability can be expected for HRM measures than with VFSS measures within sessions. Variability was higher across sessions than within session for nadir pressures and relaxation duration while variability within and across session was similar for resting pressures. No order effects within and across session (where applicable) were observed. Reasons for the difference in variability across and within session in HRM may be due to measurement stability factors and data extraction methods used that yielded poor to moderate reliability between raters. These data will provide a basis for sample size calculation for longitudinal treatment studies using UES measures as an outcome measure and contribute to normative data for HRM measurement using a small-diameter catheter.

The final study, Study 4, investigated the short-term efficacy of a swallowing rehabilitation approach, behavioural balloon dilatation (BBD) with a single patient with UES dysfunction after brainstem stroke. A 20-session BBD protocol was carried out with pre-, mid- and post-treatment assessments with VFSS and HRM. A combination of two methods of self-administered BBD was carried out with an inflated urethral balloon catheter: 1) retrograde method, where the catheter is inserted below the UES before inflating the balloon, then pulled up through the UES in synchrony with dry swallows; 2) anterograde method, where an inflated balloon is “swallowed” through the UES with aid of a guidewire. Dilatation was performed 20 to 30 times in each session, two sessions a day, five days a week. Although the original aims of the studies could not be met with a sample size of one, a trend was noted from this single-subject research. There was a greater association between peak hyoid displacement and UES opening post-treatment, suggesting the possibility of improved swallowing synchronicity. Implementing retrograde dilatation alone holds greater promise at present due to concerns with the safety of the anterograde dilatation technique. Separate from BBD, the patient demonstrated increased UES pressures during swallowing on HRM, a swallowing pattern that was inverse to that of normal behaviour. It is not clear if the phenomena observed were neurally-mediated events or maladaptive swallowing behaviours that may be characteristic of some patients with brainstem stroke.

This research programme has provided a manometric perspective of the UES and associated changes in pharyngeal swallowing dynamics following esophageal disorders, thus contributing to current knowledge of the relationship between the UES and pharynx in swallowing. While findings from the rehabilitation arm of research were equivocal in the effectiveness of BBD as a standalone UES rehabilitation approach, the study has yielded thought-provoking observations for consideration in future research.