The Rheology and Processing of fluids used to assist symptoms of Dysphasia

ByMalcolm Mackley,

Christine Rowan, Rosemary Anthony Edward Thien, Ivy Liu

Department of Chemical Engineering and BiotechnologyUniversity of Cambridge

UK

Background - Dysphagia

Mouth

Tongue

Epiglottis

Airway

Oesophagus

Background - Dysphagia

Video courtesy of Speech and Language Therapy department, Addenbrooke’s Hospital

Thickener solutions

Microscope images taken at 50x magnification of the two commercial thickeners in water with a solid fraction of 4.8%.

Nutilis

100 μm

Thicken Up

100 μm

Starch plus polymer? Starch only?

Rheological CharacterizationSteady shear; apparent viscosity

concentration 2.5g/50 ml water

Nutilis, Starch plus polymer?

Thicken Up, starch only?

Both Power Law Fluids

Oscillatory Strain Sweep Data for Nutilis and Thicken Up

Strain Sweeps (10 rad/s), solids concentration 2.5g/50 ml waterNutilis, Starch plus polymer?

Thicken Up, starch only?

Oscillatory Frequency Sweep Data for Nutilis and Thicken Up

Frequency Sweeps (1% strain), solids concentration 2.5g/50 ml water

Thicken Up, starch only?

Nutilis, Starch plus polymer?

Both viscoelastic fluids

Relaxation Spectrum from ARES Software& G’, G” Predictions

Nutilis, Starch plus polymer?

Note; long relaxation modes

Relaxation Spectrum from ARES Software- Comparison of Nutilis & Thicken Up

Thicken Up, starch only?

Note; long relaxation modes

Variation in Viscosity with Increasing Concentration

Nutilis, Starch plus polymer?

Thicken Up, starch only?

Smoothie !

Extensional Rheometry Results – Xanthan Gum

Xanthan gum: 0.5g in 50 ml water Polymer only

6000 frames per second

Frame: 1 80 131(Piston stops)

400 600 850 860 900

Classic polymer behaviour with long filament decay

Extensional Rheometry Results - Nutilis

Nutilis: 2.5g in 50 ml water, Starch plus polymer? 6000 frames per second

Frame: 1 100 120(Piston stops)

300 480 490 491 500

Unusual collapse due to non homogeneous fluid

Extensional Rheometry Results – Thicken Up

Thicken Up: 2.5g in 50 ml water, Starch only?

6000 frames per second

Filament breakage before pistons completed displacement.

Frame: 1 53 54 100

Unusual collapse due to non homogeneous fluid

The Cambridge Throat– Model Throat

“The Cambridge Throat”

Dialysis tubing is used to

model the mouth

Roller models the tongue

Epiglottis

Oesophagus – food pipe

Airway

Weight provides a constant torque, (stress)

“tongue”

The roller and pulley used to represent the tongue.

Epiglottis

Water

Water

Water

Nutilus, starch plus polymer?

Nutilus, starch plus polymer?

Nutilis Thicken up

Residence time within tube

Time from

Residence time as a function of solids concentration

0.1

1

10

0 2 4 6 8 10

Solids Concentration (wt%)

Residence time (s)

Nutilis

Thicken Up

Xanthan gum

Water

Residence time increases with increasing concentration

Residence time from epiglottis to airway

Time from epiglottis to airway as a function of solids concentration

0.01

0.1

1

10

100

0 1 2 3 4 5 6 7 8 9

Solids Concentration (wt%)

Time (s)

Nutilis

Thicken Up

Xanthan gum

Water

Residence time increases with increasing concentration

Type of Flow

Type of Flow

Constant Stress, Fluid Slug flow

J. Rheol. 484, 765-785 July/August 2004

Arjen C. B. Bogaerds, Martien A. Hulsen,Gerrit W. M. Peters, and Frank P. T. Baaijens

Stability analysis of injection molding flows

Conclusions

• Dysphagia fluids rheologically characterised.• Fluids are highly viscoelastic.• Design and build of “The Cambridge Throat”.• Residence time of fluid strongly dependant on formulation, viscoelasticity may play a role in division of flow between food and airpipe.