A Device that Models Human Swallowing

Abstract

The pharynx is critical for correct swallowing, facilitating the transport of both air and food transport in a highly coordinated manner, and aberrant co-ordination causes swallowing disorders (dysphagia). In this work, an in vitro model of swallowing was designed to investigate the role of rheology in swallowing and for use as a pre-clinical tool for simulation of different routes to dysphagia. The model is based on the geometry of the human pharynx. Manometry is used for pressure measurements and ultrasonic analysis is performed to analyze the flow profiles and determine shear rate in the bolus, the latter being vital information largely missing in literature. In the fully automated model, bolus injection, epiglottis/nasopharynx movement, and ultrasound transducer positioning can be controlled. Simulation of closing of the airways and nasal cavity is modulated by the software, as is a clamping valve that simulates the upper esophageal sphincter. The actions can be timed and valves opened to different degrees, resembling pathologic swallowing conditions. To validate measurements of the velocity profile and manometry, continuous and bolus flow was performed. The respective velocity profiles demonstrated the accuracy and validity of the flow characterization necessary for determining bolus flow. A maximum bolus shear rate of 80 s −1 was noted for syrup-consistency fluids. Similarly, the manometry data acquired compared very well with clinical studies.

Experimental and Computational Investigation of the IDDSI Flow Test of Liquids Used in Dysphagia Management

“…13,33 However, that pressure was still sufficient to achieve high shear rates (max: 7400/s in the nozzle for the thinnest Gum-thickened liquid), at least as high as has been measured or simulated during swallowing. 25,27,31 This implies that propelling these thickened liquids requires relatively very little tongue pressure in comparison to the pressure required to compress and swallow soft solid foods. 29 Therefore these results suggest that liquids up to and including the IDDSI Level 3 classification would not require excessive effort to consume, despite their reduction in gravity-driven flow speed.…”

“…shear viscosity) which has been shown to be insufficient to describe flow in practice, 19,25,27 the most fundamental property of any instrumental test is that the test condition is relevant to the application. In this case, in vivo , a bolus of liquid will experience a wide variety of shear rates during oral preparation and swallowing 25,31 ; the shear rate will be maximal at the oropharyngeal surfaces and will always reach 0 in the center of the bolus. The IDDSI flow test represents a composite measurement of flow behavior at a wide range of velocities and shear rates: slower rates for thicker liquids and faster rates for thinner liquids.…”

“…Current research using in vitro mechatronic swallow simulators is beginning to contribute to the general understanding of fluid dynamics during swallowing, aiming to improve the efficacy of texture modification as a dysphagia intervention. 9,29,31 These have provided some data indicating flow speeds decreasing with increased thickness and differences in flow between different material types. 29 A wide variety of liquid types are used in clinical practice from jelly-like gum-thickened juices to nutritional supplements with high protein and fat content.…”

Assessment of the Food-Swallowing Process Using Bolus Visualisation and Manometry Simultaneously in a Device that Models Human Swallowing

“…The in vitro simulator, called the Gothenburg Throat, is described in detail in a separate paper [26]. Nevertheless, to guide the reader, a brief account of how the simulator works is provided here (see Fig.…”

A review of the approaches to predict the ease of swallowing and post-swallow residues

“…The flow of liquid bolus is monitored by a Doppler US to yield a complete spatial description of the flow field. Limited experimental results were published in (Qazi and Stading, 2017) and more results have become available only when this review was already in press ((Stading et al, 2019)).…”