Thickened Liquids for Dysphagia Management: a Current Review of the Measurement of Liquid Flow

Analytic Approaches to Physicochemical Properties of Materials for Biomedical Applications Across Nanoscopic and Macroscopic Length Scales

The design and implementation of biomedical devices for both diagnostic and direct medical applications have revolutionized patient care, paving the way for improved patient outcomes. Understanding the characteristics of materials used in the design of new devices is essential for their advancement. In this review, our goal is to assist biomedical researchers in appreciating the importance of these properties and the role of selecting the proper measurement. We discuss how the nanoscopic molecular composition, arrangement, and interactions generate the properties of liquids, solids, viscoelastic materials, and colloids and discuss the measurement techniques that can be used to assess these properties from the nanoscale to the macroscale. We explore the linear and nonlinear mechanical responses of materials, elucidate their behaviors under varying conditions, and discuss corresponding measurement techniques. Finally, we highlight the importance of tailoring measurements to the underlying biological processes and applications being investigated.

Characterization of Beverage Viscosity Based on the International Dysphagia Diet Standardisation Initiative and Its Correspondence to the Japanese Dysphagia Diet 2021

Background/Objective: The International Dysphagia Diet Standardisation Initiative (IDDSI) and the Japanese Dysphagia Diet 2021 (JDD2021) are prominent systems that classify thickened beverages for dysphagia management. We herein aim to establish a correspondence between these systems through systematic viscosity measurements. Methods: We analyzed 49 thickened beverage samples using an E-type viscometer, IDDSI flow test, and JDD syringe test. Results: Receiver operating characteristic analysis revealed the following viscosity cutoffs for IDDSI levels: 0-1 at 72.0 mPa·s (area under the curve [AUC] 0.94), 1-2 at 112.0 mPa·s (AUC 0.95), and 2-3 at 303.0 mPa·s (AUC 0.97). Multiple regression analysis revealed that beverage characteristics, including fat, sodium content, and settling time, significantly influenced viscosity (R2 = 0.803). The findings established that IDDSI Level 0 corresponds to a thinner viscosity than JDD Stage 1 and Stage 1 (0-72 mPa·s), Level 1 to Stage 1 (72-112 mPa·s), Level 2 to Stages 1-2 (112-303 mPa·s), and Level 3 to Stage 3 (>303 mPa·s). Moreover, the measurement methods had high correlations (r = 0.83-0.93, p < 0.001). Conclusions: The comprehensive map between IDDSI and JDD2021 classifications developed from the results of this study enables healthcare providers to translate between the classification systems, improving dysphagia management internationally while supporting evidence-based care and global research.

The influence of temperature variation on the levels of the International Dysphagia Diet Standardization Initiative

PURPOSE

To analyze the influence of temperature on the flow/texture of different foods, immediately after preparation and after one hour, and 2) To compare the influence of varying the cook in food preparation, in relation to food flow.

METHODS

This is a quantitative and experimental study. The IDDSI standardized flow test was used to evaluate the remaining volume in the syringe and the levels of foods (porridge, smoothie, liquid soup, and pureed light soup) prepared by different cooks, in triplicate, at time zero (T0) and after one hour (T1).

RESULTS

Differences in temperature were observed in all foods at T0 and T1 (p < 0.05). The IDDSI level changed only in porridge, from level 3 to 4 (p = 0.043). Modifications were observed in the preparation by different cooks for smoothie, on the 2nd and 3rd day (p = 0.049), from level 3 to 4 of IDDSI. In porridge, on the 1st and 3rd day (p = 0.048) and 2nd and 3rd day (p = 0.048), with a change from level 4 to 3 of IDDSI.

CONCLUSION

The temperature of all foods differed within the one-hour interval, with modifications in the flow test and in the IDDSI levels, from level 3 to 4, only for porridge. Different cooks prepared the smoothie and porridge with different characteristics, resulting in changes from level 3 to 4 in both foods.

Getting the consistency right in thickened liquids using Viscgo Sticks: A validation study

BACKGROUND

Dysphagia is a condition whereby a person's ability to swallow, eat and drink is impacted. One strategy to manage dysphagia and aid safe swallowing is the modification of food and drink, including using thickening agents to thicken drinks. Drinks are thickened to levels appropriate to a person's swallowing abilities and the underutilised 'syringe flow test' is currently the recommended method for checking thickness levels. Viscgo Sticks were developed as a practical alternative to the flow test.

METHODS

This is a real-world validation study designed to determine validity and reliability of Viscgo Sticks. Independent researchers and healthcare professionals tested Viscgo Sticks (Viscgo Limited) against the flow test in three levels of thickened drinks. Researchers also conducted tests with different thickening agents and different drink types: water, milk, orange juice and hot tea.

RESULTS

The intra- and inter-rater reliability of Viscgo Sticks was moderate to almost perfect (κ = 0.45-0.98) within and between researchers and substantial (κ = 0.66-0.67) within and between healthcare professionals. When tested by researchers and healthcare professionals against the flow test, Viscgo Sticks correctly classified 83.33%-100% of thickened drinks with high accuracy (area under curve = 0.70-1.00).

CONCLUSIONS

A simple and reliable tool like Viscgo Sticks, which can verify a prescribed thickness level of liquid, is invaluable in healthcare settings where day-to-day drink preparation occurs. Overall, Viscgo Sticks provide a reliable and valid means to test thickened drinks in clinical practice with a few exceptions identified.

Sodium Phenylbutyrate and Taurursodiol: A New Therapeutic Option for the Treatment of Amyotrophic Lateral Sclerosis

OBJECTIVE

To review the safety and efficacy of sodium phenylbutyrate and taurursodiol (SP + T) in slowing progression of amyotrophic lateral sclerosis (ALS) compared with pre-existing therapies.

DATA SOURCES

A PubMed (from January 1, 2009, to April 13, 2023) and ClinicalTrials.gov search conducted using sodium phenylbutyrate, taurursodiol, AMX0035, riluzole, and edaravone. Additional articles were identified by hand from references.

DATA SELECTION AND DATA EXTRACTION

This included English-language articles evaluating SP + T efficacy or safety in humans for decreasing neuronal death and slowing the progression of ALS.

DATA SYNTHESIS

In one phase II clinical trial that encompassed an open-label extension phase, disease severity, assessed by the rate of decline in overall score on the Amyotrophic Lateral Sclerosis Functional Rating Scale-Revised with higher scores indicating more functional ability, was -1.24 points per month with active drug and -1.66 points per month with placebo (difference, 0.42 points per month; 95% CI, 0.03-0.81; P = 0.03). Post hoc analysis found survival benefit of median 4.8 months with active medication compared with placebo.

RELEVANCE TO PATIENT CARE AND CLINICAL PRACTICE IN COMPARISON WITH EXISTING DRUGS

SP + T is a new US Food and Drug Administration-approved oral suspension for the treatment of ALS. Patients who received active medication through the phase II trial showed decreased rates of disease progression. Overall, SP + T could be considered a potential agent for the treatment of ALS which has a high unmet need.

CONCLUSION

SP + T is an option for the treatment of ALS; however, additional data regarding efficacy in phase III trials with long-term safety profile considerations, as well as trials to compare current therapy with SP + T, are needed.

Flow test by the International Dysphagia Diet Standardization Initiative reveals distinct viscosity parameters of three thickening agents

The International Dysphagia Diet Standardization Initiative (IDDSI) flow test is useful for the global standardization of food consistencies of dysphagia patients. In clinical practice, different compositions of food thickeners are commonly used, directly influencing viscosity parameters and swallowing physiology. We aimed to compare the IDDSI thickness levels, remaining volume in the syringe (RVS), and viscosity parameters of three different food thickeners. As a secondary objective, we compared the cost of preparing 100 mL of thickened drinks using the studied thickeners. Thickeners A (xanthan gum), B (corn starch, tara gum, xanthan gum, and guar gum), and C (corn starch) were prepared in increasing concentrations from 1 to 7 g/100 mL and were assayed in quintuplicate using the IDDSI flow test. Thickeners A, B, and C presented statistically different results for the IDDSI levels, RVS, and viscosity parameters at all concentrations. Thickener A reached higher levels in the IDDSI framework, RVS, and viscosity parameters compared with thickeners B and C. A large range of RVS was observed at different concentrations for thickener B compared with C. Regarding viscosity, thickeners B and C, with corn starch in their composition, showed exponential behavior as concentrations increased, while thickener A presented a linear trend. The thickener composition was significantly influenced by IDDSI classification, RVS, and viscosity parameters. The study shows that xanthan gum thickeners present less variability in IDDSI, RVS, and viscosity compared with starch-based thickeners.

Instrumental and sensory techniques to characterize the texture of foods suitable for dysphagic people: A systematic review

The interest to characterize texture-modified foods (TMFs) intended for people with oropharyngeal dysphagia (OD) has grown significantly since 2011. Several instrumental and sensory techniques have been applied in the analysis of these foods. The objective of the present systematic review was to identify the most appropriate techniques, especially for the food industry and clinical setting. The search was carried out in three online databases according to the "Preferred Reporting Items for Systematic Reviews and Meta-Analyses" (PRISMA). Across the multiple trials reviewed, Texture Profile Analysis and the Uniaxial Compression Test were most used as the instrumental technique for solid foods, and the Back Extrusion Test for fluid and semisolid foods. All trials used descriptive analysis as the sensory technique. However, the experimental conditions of the trials lacked standardization. Consequently, the results of the trials were not comparable. To properly characterize the texture of TMFs intended for OD by each technique, an international consensus is needed to establish standardized experimental conditions. Methods based on these techniques should also be validated by collaborative studies to verify repeatability, replicability, and reproducibility.

How Accurate Are the Consistency Labels Used in Hong Kong? An Objective Study of the Consistency of Thickened Liquids Using International Dysphagia Diet Standardisation Initiative and Consistometric Measurements

OBJECTIVES

The present study objectively examined the consistency (thickness) of labels that are used in Hong Kong for the population with dysphagia using an International Dysphagia Diet Standardisation Initiative (IDDSI) flow test and Bostwick consistometric measurements.

METHODS

Liquids were prepared by thickening water to achieve 4 consistency labels (slightly thick, mildly thick, medium thick, and extra thick) according to manufacturer's instructions, employing 2 types of thickening products that are used in Hong Kong, i.e., starch based and gum based. For each consistency label prepared using each thickening product, the IDDSI flow test and consistometric measurements were obtained and compared.

RESULTS

The results showed that the actual thickness of liquids was highly dependent on the type of thickener (starch based vs. gum based) used. Thickened liquids prepared using the starch-based thickener were generally thinner than the actual value at a lower concentration.

CONCLUSION

Though prepared strictly following the manufacturer's instructions, the thickened liquids fail to faithfully correlate with the standardized norms established according to the IDDSI framework and the objective consistometric measurement using a Bostwick consistometer. Therefore, caution must be exercised when administering a thickened diet following the manufacturer's instructions for patients with dysphagia.

Food polysaccharides and roles of rheology and tribology in rational design of thickened liquids for oropharyngeal dysphagia: A review

In today's market environment, an aging society is recognized as one of the megatrends in the world. The demographic change in the world population age structure has driven a huge demand in healthcare products as well as services that include the technological innovation for the health and wellness of the elderly. Dysphagia or swallowing difficulty is a common problem in the elderly as many changes in swallowing function come with aging. The presence of a strong relationship between swallowing ability, nutritional status, and health outcomes in the elderly leads to the importance of dysphagia management in the population group. Modification of solid food and/or liquid is a mainstay of compensatory intervention for dysphagia patients. In this regard, texture-modified foods are generally provided to reduce risks associated with choking, while thickened liquids are recommended for mitigating risks associated with aspiration. In this review, we discuss thickened liquids and other issues including the importance of their rheological and tribological properties for oropharyngeal dysphagia management in the elderly. The review focuses on both commercial thickeners that are either based on modified starch or xanthan gum and other potential polysaccharide alternatives, which have been documented in the literature in order to help researchers develop or improve the characteristic properties of thickened liquids required for safe swallowing. Furthermore, some research gaps and future perspectives, particularly from the nutrition aspect related to the interaction between thickeners and other food ingredients, are suggested as such interaction may considerably control the rate of nutrient absorption and release within our body.

Assessment of tomato-based thick fluid diet for patients with dysphagia using a simple and cheap test

Swallowing difficulty, also known as dysphagia, is a health condition that can be managed by different approaches, such as changing the viscosity of fluid foods with thickener agents. Tomato-based beverages such as "gazpacho" and "salmorejo" are common foods much appreciated by the populations that adopt a Mediterranean diet, mainly in Spain. These beverages usually present a low viscosity, challenging to include in diets for dysphagia patients. Thus, this work aimed at evaluating the flow properties of tomato-based beverages with or without the addition of thickener agents (based on maltodextrin or gum) using a simple and cheap method proposed by the International Dysphagia Diet Standardization Initiative (IDDSI) to verify the suitability of using those products in a diet of patients with dysphagia. The study also evaluated the differences in using BD-type syringes on the test. Results indicated that the type of thickener significantly (p < .05) affects the samples' flow properties, enhancing their rheological behavior. The type of syringe can also affect the results, as they present different Luer slip tips. The results revealed that tomato-based beverages may have their properties improved simply by using low amounts of thickener agents (1.2-3.0 g 200 ml^-1 ) and that the IDDSI test can be an alternative, cheap and straightforward method for evaluating these types of foods in hospital environments. Including tomato-based beverages in the diet of patients with dysphagia may present many benefits as these products have a rich nutritional composition (fiber) in addition to biocompounds such as lycopene and phenolic compounds.

Texture-Modified Food for Dysphagic Patients: A Comprehensive Review

Food texture is a major food quality parameter. The physicochemical properties of food changes when processed in households or industries, resulting in modified textures. A better understanding of these properties is important for the sensory and textural characteristics of foods that target consumers of all ages, from children to the elderly, especially when food product development is considered for dysphagia. Texture modifications in foods suitable for dysphagic patients will grow as the numbers of elderly citizens increase. Dysphagia management should ensure that texture-modified (TM) food is nutritious and easy to swallow. This review addresses how texture and rheology can be assessed in the food industry by placing particular emphasis on dysphagia. It also discusses how the structure of TM food depends not only on food ingredients, such as hydrocolloids, emulsifiers, and thickening and gelling agents, but also on the applied processing methods, including microencapsulation, microgels as delivery systems, and 3D printing. In addition, we address how to modify texture for individuals with dysphagia in all age groups, and highlight different strategies to develop appropriate food products for dysphagic patients.

Rheological and Nutritional Assessment of Dysphagia-Oriented New Food Preparations

Dysphagia that involves difficulty swallowing food and liquids is a symptom of different diseases. In some cases, patients who experience this symptom should be fed with modified consistency foods. Dysphagia is often accompanied by malnutrition and dehydration and an interesting approach to dealing with these conditions is to provide patients with nutrient-rich foods. In this study, two new food formulations for dysphagia patients are proposed: a cereal-based protein meal and a vegetable cream. The nutritional and rheological characteristics of the two innovative preparations were assessed and compared with those of commercial products. The proposed protein meal formulations meet the criteria for the “high protein” claim and the vegetable cream meets those of the “source of fiber” claim. The rheological investigation revealed that the flow properties of the innovative formulations were comparable to those of the commercial ones. Based on these preliminary outcomes, this investigation represents an interesting perspective potentially valuable to enlarge the offer of possibilities for people suffering from swallowing disorders.

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

Thickened fluids and texture-modified foods are commonly used in the medical management of individuals who suffer from swallowing difficulty (known as dysphagia). However, how to reliably assess texture properties of such food systems is still a big challenge both to industry and to academic researchers. This article aims to identify key physical parameters that are important for objective assessment of such properties by reviewing the significance of rheological or textural properties of thickened fluids and texture-modified foods for swallowing. Literature reviews have identified that dominating textural properties in relation to swallowing could be very different for thickened fluids and for texture-modified foods. Important parameters of thickened fluids are generally related with the flow of the bolus in the pharyngeal stage, while important parameters of texture-modified foods are generally related with the bolus preparation in the oral stage as well as the bolus flow in the pharyngeal stage. This review helps to identify key textural parameters of thickened fluids and texture-modified foods in relation to eating and swallowing and to develop objective measuring techniques for quality control of thickened fluids and texture-modified foods for dysphagia management.

Is IDDSI an Evidence-Based Framework? A Relevant Question for the Frail Older Population

To delay impacts of aging, optimal nutritional status is essential. Several factors can reduce food intake, such as isolation, income, and cognitive/physical decline. Additionally, chewing and swallowing difficulties, or dysphagia, often disrupt the ability to consume life-long favorite dishes. Food and liquids could require modification of texture or consistency to ensure a comfortable or safe swallow. The food industry, foodservices facilities, and caregivers need quality control benchmarks to provide adequate nourishment and meet these new feeding challenges. The International Dysphagia Diet Standardisation Initiative (IDDSI) is proposing the IDDSI framework and testing methods to describe food used in nutritional care plans to circumvent dysphagia and improve communication among caregivers. This systematic review assesses the validity and reliability of the IDDSI testing methods using the Consensus-based Standards for the selection of health Measurement Instruments (COSMIN). Two publications presented content validity whereas 19 publications looked at construct validity or reliability for the IDDSI testing methods. One study was conducted in older adults presenting dysphagia. This review concludes that there is insufficient evidence to recommend the IDDSI testing methods. Further research, conducted with robust methodological design and reporting, is needed to develop and assess nutritious adapted food for frail older populations.

Riluzole Oral Suspension for the Treatment of Amyotrophic Lateral Sclerosis: Texture and Compatibility with Food Thickeners Evaluation

Riluzole 5 mg/mL oral suspension is the only licensed liquid medicine to treat Amyotrophic Lateral Sclerosis (ALS) orally. As more than 80% of ALS patients develop dysphagia, an oral liquid formulation provides an important therapeutic option. The Riluzole 5 mg/mL oral suspension is administered by means of the graduated oral dosing syringe included in the medicine package. Its concentration (5 mg/mL) is consistent with a small and easy to measure volume (10 mL) to deliver the prescribed 50-mg dose twice daily. This work had a dual objective. The first was to evaluate the texture of the Riluzole 5 mg/mL oral suspension according to the International Dysphagia Diet Standardisation Initiative (IDDSI) flow test. Results of this experiment indicated that Riluzole 5 mg/mL oral suspension would basically fall under the “mildly thick” IDDSI descriptors. This is an important feature because thick fluids facilitate a safer swallow in patients with dysphagia. As a second objective, we evaluated for scientific purposes the compatibility of Riluzole 5 mg/mL oral suspension with some of the most common food thickeners available on the market. Intimate mixtures of the Riluzole 5 mg/mL oral suspension with thickeners were evaluated for appearance, pH, Riluzole assay and Riluzole related substances immediately after preparation and after two hours at room temperature. Riluzole 5 mg/mL oral suspension resulted to be compatible with all the marketed thickeners tested.

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

The International Dysphagia Diet Standardisation Initiative (IDDSI) flow test, using a standard 10-mL syringe, is being adopted in many countries for clinical measurement of the consistency of drinks. The working hypothesis is that thickening drinks to retard flow can be advantageous for individuals who struggle to cope with thin drinks. This study assesses how the IDDSI test relates to rheology and clinical knowledge of physiological flows during swallowing. With no pre-existing analytical solution for internal flow through the syringe, a computational model was designed, incorporating rheometry data from a variety of Newtonian and non-Newtonian liquids. The computational model was validated experimentally across the range of liquids but the technique showed limitations in simulating dripping and cohesiveness. Gum-based liquids which were strongly shear-thinning (0.12 < n < 0.25) showed plug-flow characteristics with 90% of the shear occurring in only 22% of the radial dimension. Shear rates were maximal at the nozzle outlet (> 60 times higher than the barrel) and reached 7400/s for the thinnest gum-based liquid. Shear rheology data alone was unable to describe the flow of these drinks. The flow conditions in the test varied according to the type and consistency of liquid, relating to the desired clinical effect.