Development of a bioimpedance-based swallowing biofeedback device with smart device integration.
Thesis DisciplineElectrical Engineering
Degree GrantorUniversity of Canterbury
Degree NameMaster of Engineering
Low resolution pharyngeal manometry is an invasive diagnostic method that has recently been used as a biofeedback device for swallowing rehabilitation. The University of Canterbury Rose Centre uses pharyngeal manometry to diagnose and rehabilitate subjects who suffer from pharyngeal mis-sequencing. Pharyngeal mis-sequencing occurs when pressure is applied simultaneously throughout the pharynx rather than sequentially. Rehabilitation can only be performed in clinic due to the need for specialized equipment and trained staff, and the invasiveness of the test limits the time that can be spent training. As an alternative method to measure the pharyngeal pressure sequence, bioimpedance has been investigated by a previous University of Canterbury Master’s student. A prototype was developed that measured bioimpedance in two locations as a proxy for pharyngeal pressure sequence. The prototype device named GULPS (Guided Utility for Latency in Pharyngeal Swallowing), measured a change in impedance during swallowing. However, the features of this waveform were inconsistent and were not present during every swallow. The frequency of the current that passes through tissue affects its path through the tissue, therefore impacting the measured impedance. To improve the consistency of the impedance measurement, the effect of current injection frequency was investigated. A modular-hardware system was created from the original design to allow testing of different injection frequencies. The hardware was further developed by replacing the method of generating the constant amplitude current injection signal. The improvement to the design resulted in a differently-shaped waveform to that of the previous prototype, including a new feature. This feature is a single peak that occurred in both channels and was reproduced in every swallow. Experimentation showed that the features were not obviously frequency dependent. The separation between the peaks of the two impedance channels was compared with the separation between the two pressure peaks recorded during simultaneous pharyngeal manometry but there was no significant correlation between the two measures of peak-peak separations. Two alternative hardware/signal conditioning changes were trialled: electrical isolation of each channel and a subtraction method, which aims to remove the effect of the changing impedance between the two electrode channels. Electrical isolation of the two channels had no effect on the impedance waveforms. However, the subtraction method produced a different output and requires further investigation as the output was inconsistent. Bluetooth communication was integrated into the GULPS hardware, and a corresponding Android Application (App) was written. The developed App was successful in displaying the impedance measurement output and adds greater user flexibility, allowing the user to interface with the bioimpedance measurement hardware from their tablet or phone. With no measured significant correlation between GULPS and pharyngeal manometry, further research needs to be performed to better relate the features measured by GULPS to those seen during pharyngeal manometry. Until this can be achieved, the GULPS device cannot replace pharyngeal manometry for biofeedback-based rehabilitation of pharyngeal mis-sequencing.