Relationship between Syringe Flow Measurements and Viscosity of Nectar-Thick Beverages for Dysphagia Management

Abstract

Commercial cold beverages thickened with a xanthan gum (XG)-based food thickener were examined at different thickness levels by using the simple, cost-effective syringe flow test (SFT) developed by the International Dysphagia Diet Standardization Initiative (IDDSI). We prepared cold thickened beverage (CTB) samples with different thickener concentrations and measured them by extrapolating the viscosity range (51–350 mPa·s) for nectar-like consistency. CTBs were also measured via the line-spread test (LST), and the flow distance value (cm) by LST and the volume remaining (mL) in the syringe by SFT was correlated with the apparent viscosity (ηa,50). Plots comparing ηa,50 with SFT or LST values showed good exponential relationships between the measurements. The SFT showed a better relationship (R2 = 0.928) than LST (R2 = 0.825), indicating that the former can predict the viscosity better in the range for nectar-like consistency. In particular, the SFT showed a significant difference (R2 = 0.964) compared to the LST (R2 = 0.709) for thickened protein-based beverages. These results suggest that the SFT using the IDDSI methodology is a more suitable instrument than the LST for accurately evaluating the viscosity of XG-based CTBs with nectar-like consistency.

Effect of Setting Time on Viscosity Stability of Xanthan Gum- and Starch-Based Thickened Beverages for Patients with Dysphagia: Comparison of IDDSI Syringe Flow Test and Line-Spread Test

“…On the other hand, the syringe tip with a small diameter used in SFT could be partially or entirely obstructed by particulates formed by the complex interaction between different components of thickeners and beverages (Table 2), potentially impeding the flow of thickened beverages in the syringe (Hadde et al, 2015;Weston and Clarke, 2020). Additionally, the high friction resulting from the direct contact between the syringe surface and the thickened beverage might hinder the outflow of the thickened beverage contained in the syringe (An et al, 2023). These effects of particulates and friction might explain why the SFT value stabilized faster than the LST value at level 3, despite the opposite result observed at level 2 (Table 3).…”

“…Several studies have also reported a strong exponential relationship between the LST values of thickened beverages and the rheological properties relevant to fluid viscosity ( Nicosia and Robbins, 2007 ; Kim et al, 2014b ; Kim et al, 2018 ). One common approach to compare the thickness of thickened fluids involves measuring the average flow distance in the quadrant directions of thickened fluid poured into a cylindrical container ( Mann and Wong, 1996 ; Nicosia and Robbins, 2007 ; Barbon and Steele, 2018; Kim et al, 2018 ; Giura et al, 2021; Jeong et al, 2021 ).…”

“…However, these guidelines are overly simplistic and inaccurate. Moreover, several studies found that various factors, including setting time ( Dewar and Joyce, 2006 ; Kim et al, 2014b ; Kim and Yoo, 2015 ), beverage type ( Kim et al, 2014a ; Yoon and Yoo, 2017 ; Jeong et al, 2021 ; An et al, 2023 ), and thickener type ( Dewar and Joyce, 2006 ; Kim et al, 2014a ; Kim et al, 2018 ), are closely linked to the η a,50 values of thickened beverages as determined using rheometers. These factors often result in failure to achieve the desired viscosity.…”

“…The National Dysphagia Diet (NDD) Task Force has standardized fluid diets for patients with dysphagia using apparent viscosity at a shear rate of 50 s −1 (a,50), which was determined using precision-controlled rheometers (Kim et al, 2014b;Bolivar-Prados et al, 2022;An et al, 2023). However, these instruments are unfamiliar to individual patients, caregivers, or clinics, which limits the practical application of NDD standards (Kim et al, 2014b).…”

Neuromuscular electrical stimulation improves swallowing initiation in patients with post-stroke dysphagia

“…During the eating process, foods with lower viscosity are more likely to cause penetration and aspiration ( Newman et al, 2016 ). As a result, caregivers often thicken the food of the dysphagia patients ( Watanabe et al, 2018 ), but the thickened food can make it more difficult for the patient to transport it through the mouth ( Jeong et al, 2021 ), which can cause the food to stay in their mouth longer. For patients with oral transit difficulties and delayed swallowing initiation, the longer the food stays in the oral cavity, the higher the degree of hydrolysis by salivary amylase even if the food is thickened ( Abu-Hasan et al, 2014 ; Sole et al, 2020 ).…”