The role of extensional rheology in the oral phase of swallowing: an in vitro study

Abstract

Swallowing disorders deteriorate significantly the quality of life and can be lifethreatening. Texture modification using shear thinning food thickeners have proven effective in the management of dysphagia. Some studies have recently considered the positive role of cohesiveness, but there is still an insufficient understanding of the effect of the rheological properties of the liquid bolus on the dynamics of bolus transport, particularly when elasticity and extensional properties are combined with a shear thinning behaviour. This study combines steady shear, SAOS and capillary breakage extensional rheometry with an in vitro method to characterize the oral transport of elastic liquids. Bolus velocity and bolus length were measured from in vitro experiments using image analysis and related to the shear and extensional properties. A theory describing the bolus dynamics shows that the elastic and extensional properties do not influence significantly the oral transit dynamics. Conversely, in vitro results suggest that the extensional properties can affect the transition from the oral to the pharyngeal phase of swallowing, where thin, viscoelastic liquids lead to a fast transit, lower oral post-swallow residues and more compact bolus with a smoother surface, which may suggest a lower risk of fragmentation. This mechanistic explanation suggests that the benefit of the extensional properties of thin viscoelastic liquids in the management of dysphagia should be further evaluated in clinical trials.

Effect of the rheological properties of the liquid carrier on the in vitro swallowing of solid oral dosage forms

“…Compared to TUC and PEO, the oat extracts had an intermediate shear thinning behavior. Similar results were reported by Marconati and Ramaioli (2020).…”

“…In the experimental conditions of this study, the oat extracts had larger λ c than the PEO suspensions (0.04–0.10, and 0.01–0.07, respectively, as presented in Appendix 1). Similar results were obtained by Marconati and Ramaioli (2020).…”

“…Schematics of the in vitro setup used to replicate the oral phase of swallowing, adapted from Marconati and Ramaioli (2020)…”

“…There is a general agreement that texture modification of liquids using shear thinning food thickeners promotes safe swallowing and helps managing dysphagia (Newman, Vilardell, Clavé, & Speyer, 2016; Rofes, Arreola, Mukherjee, Swanson, & Clavé, 2014), but the role of elastic and extensional properties of fluids on the dynamics of bolus transport has only recently been investigated and is still not fully understood (Hadde, Chen, & Chen, 2020; Hadde, Cichero, Zhao, Chen, & Chen, 2019; Mackley et al, 2013; Marconati & Ramaioli, 2020; Nishinari, Turcanu, Nakauma, & Fang, 2019; Qazi, Ekberg, Wiklund, Mansoor, & Stading, 2020; Sukkar, Maggi, Travalca Cupillo, & Ruggiero, 2018). In a previous study, we observed that elastic and extensional properties of thickened liquids play a significant role during bolus ejection from an in vitro oral cavity (Marconati & Ramaioli, 2020). Bolus elongation during in vitro swallowing and post‐swallow residues were limited with thin elastic liquids, suggesting a lower risk of fragmentation in vivo.…”

Texture and texture assessment of thickened fluids and texture‐modified food for dysphagia management

“…Patel et al (2019) measured the bolus elongation in‐vitro using a physical model of artificial throat, “Cambridge Throat”. Furthermore, a recent article by Marconati and Ramaioli (2020) examined the role of extensional rheology in‐vitro study and suggested that the extensional properties can affect the transition from the oral to the pharyngeal phase of swallowing, where less elongated bolus in the oral phase lead to a fast transit and more compact bolus, which may suggest a lower risk of post‐swallow residue.…”