Conclusions

The primary objective for thickening of beverages for dysphagia management is to slow down the flow to give the impaired physiology time to react and perform the necessary functions of the pharynx, to close the opening to the airways by the epiglottis, to keep the breath by closing the vocal cords, and to open the UES. A further objective is to alleviate or prevent aspiration. Our results show thickening can be achieved in several ways, and that the mechanism of thickening matters for how effective the fluid is to prevent aspiration.

From a nutritional perspective, it may be tempting to thicken a fluid with maltodextrin as it is then possible to add much energy in the form of carbohydrates yet keeping viscosity at a reasonable level. However, the results show that this results in a Newtonian fluid, and Newtonian thickening is less effective than shear‐thinning or elastic mechanisms to avoid aspiration. The results further show that adding elasticity (Boger fluid) induces cohesiveness to the bolus, thus preventing the aspiration a Newtonian fluid with the same shear viscosity shows. Cohesiveness is further improved in the shear‐thinning fluid, which in addition to the shear‐thinning character, also is elastic.

By using a combination of dimensionless numbers for a Bolus cohesivity number the cohesivity can be quantified, with a high number indicating cohesivity. This is a preliminary hypothesis which needs to be evaluated on larger data sets for more fluids, but it correlates well with observed cohesivity.

The limited experimental data set should be extended, but the results on the important mechanisms are still clear. The set of model fluids should also be evaluated sensorily regarding swallowing using panels of older adults who preferably have or can detect dysphagia symptoms. From a dysphagia management perspective, many of the commercially available thickeners are already based on xanthan which is positive, but the results open up opportunities for further improvement.