Assessment and behavioural modulation of the upper oesophageal sphincter in healthy swallowing.
Thesis DisciplineSpeech and Language Sciences
Degree GrantorUniversity of Canterbury
Degree NameDoctor of Philosophy
Timely and adequate opening of the upper oesophageal sphincter (UES) during swallowing is critical for safe and efficient bolus transfer from the pharynx into the oesophagus. At rest, the occluded UES functions as an important barrier between the pharynx and oesophagus. UES impairment may lead to severe consequences such as aspiration. In clinical practice, the role of speech-language therapists involves comprehensive assessment of UES function and, if indicated, specific treatment. The use of instrumentation is required for diagnostic purposes as the UES is not visible externally. This PhD programme of research involved two studies focussing on instrumental assessment of UES function. One methodological study investigated the potential of new ultrasound technology for evaluation of hyolaryngeal excursion, a biomechanical event of interest in the assessment of UES function. A second methodological study evaluated the current state of practice in the use of high-resolution manometry (HRM) that is an emerging technology in the assessment of pharyngeal and UES pressure. While clinicians rely on optimised instrumental assessment of UES function, rehabilitation approaches that address underlying pathophysiology are as important. There are limited behavioural treatment options for impaired pressure regulation. Hence, studies to explore potential new avenues in the rehabilitation of UES function are necessary. The exploratory study of this PhD research focuses on volitional modulation of UES pressure in healthy subjects to build a foundation for potential future behavioural treatment avenues.
The use of ultrasound allows for radiation-free assessment of hyolaryngeal excursion, a biomechanical event that contributes substantially to UES opening. Reported validity and reliability data are promising for this purpose. Despite this, the use of ultrasound devices has not translated into routine clinical practice for deglutition. Newly developed, pocket-sized ultrasound systems may facilitate clinical translation, but image quality requires evaluation. Thus, validity and reliability testing of this newer technology in the assessment of hyolaryngeal excursion was completed in a cohort of 20 healthy participants. Validity was quantified using correlation analysis to similar measures derived from videofluoroscopic swallowing study. Reliability was evaluated within and across raters as well as over time using the intra-class correlation coefficient (ICC) and standard error of measurement (SEM). Findings of insufficient validity and reliability suggest that pocket-sized ultrasound equipment may not yet meet the standards of larger, more expensive ultrasound devices.
Assessment of pressure at the UES may be critical to evaluate underlying pathophysiology of UES dysfunction. The use of pharyngeal HRM in the assessment of pharyngeal swallowing is in early stages; thus, there are limited methodological standards. Yet, methodological aspects of data acquisition and analysis may have a considerable impact on measurement. A systematic review was conducted to summarise and appraise the methodology reported in studies using pharyngeal HRM, with and without impedance, in adult populations. Among the 62 manuscripts that met the inclusion criteria, great variability in reported methodology was apparent. Further, a striking number of manuscripts provided insufficient methodological information. Unfortunately, interpretation of data and eventual development of measurement standards are restricted if reports of methodology are lacking.
There are data to suggest that aspects of UES function, including UES opening duration or pressure at the UES during swallowing, can be indirectly altered by volitional manipulation of pharyngeal biomechanics and pharyngeal pressure generation (Hoffman et al., 2012). However, it is unknown whether pressure at the UES can be directly modulated. The potential for volitional modulation of pressure at the UES by healthy adults was investigated. Twelve participants attended one-hour training sessions, daily over two weeks. A single follow-up session was completed after a training break of two weeks. One group of participants (n = 6) was asked to volitionally increase and decrease UES resting pressure, the other group of participants (n = 6) was instructed to prolong pressure related UES opening during swallowing. During training, HRM was used as a biofeedback modality; no instruction was purposefully given regarding how to achieve the task goal. The findings suggested the potential for healthy adults to increase UES resting pressure following training. Further, results indicated that participants were able to behaviourally increase pressure related UES opening duration; yet, this was not enhanced by daily training.
This research addresses the ongoing need for optimised instrumental assessment of UES function by exploring the viability of new ultrasound technology for this purpose. Further, data of this programme of research provide a foundation for enhanced use of pharyngeal HRM in the assessment of UES pressure. Finally, this is the first programme to investigate the potential for direct behavioural pressure modulation at the UES in healthy subjects. These data may provide grounds for potential behavioural treatment options for UES impairment.