Comparative study of IDDSI flow test and line-spread test of thickened water prepared with different dysphagia thickeners

Study on Starch-Based Thickeners in Chyme for Dysphagia Use

A dysphagia diet is a special dietary programme. The development and design of foods for dysphagia should consider both swallowing safety and food nutritional quality. In this study, we investigated the rheological properties (viscosity, thixotropy, and viscoelasticity), textural properties, and swallowing behaviour of commercially available natural, pregelatinised, acetylated, and phosphorylated maize starch and tapioca starch. The results showed that all the samples belonged to food grade 3 in the framework of the International Dysphagia Dietary Standardization Initiative (IDDSI) and exhibited shear-thinning behaviour in favour of dysphagia patients, except for the sample containing pregelatinised starch, which was grade 2. Rheological tests showed that the samples had good structural recovery properties. At the same starch concentration, the elastic modulus of phosphorylated cassava starch FSMP was significantly greater than that of the starch solution, whereas that of acetylated starch was significantly less than that of the starch solution, and the combination of acetylated starch and protein led to a significant viscosity reduction phenomenon, resulting in FSMPs with good stability and fluidity; this may provide an opportunity for the incorporation of more high-energy substructures. The textural results showed that all the samples possessed textural properties of low hardness, low adhesion, and high cohesion, all of which could be used as food for dysphagia patients. This study may provide a theoretical basis for the creation and design of novel nutritional foods for dysphagia.

Difference in Drinking Times as a Function of Liquid Consistency in Adults With Oculopharyngeal Muscular Dystrophy: A Comparative Study Using Bostwick Consistometer and IDDSI Flow Test Methods

The main objective was to document the differences between drinking times and oral perception between liquids in individuals with dysphagia. A second objective was to assess variations in consistency categorization across instruments. A third objective was to explore the relationship between drinking time and dysphagia severity. A sample of individuals with OPMD (n = 30; 40-75 years) was recruited. Participants drank 80 mL of water, followed by three blinded commercially pre-thickened cranberry cocktails (CranA, CranB, CranC). Flow rates were measured with Bostwick consistometer, IDDSI Flow Test, and Discovery HR 20 rheometer. Patient-reported outcome measures were used to assess dysphagia. Mean drinking times for participants with OPMD were as follows: 7.9 ± 4.4 s for water, 10.7 ± 4.8 s for CranA, 12.3 ± 5.7 s for CranB, and 15.2 ± 7.2 s for CranC. All four times were statistically different from each other. Participants reported noticeable differences in oral perception. The Bostwick flow rates were different for all three cocktails. Based on IDDSI Flow Test, CranA was categorized as IDDSI level-2, while both CranB and CranC were categorized as IDDSI level-3. Correlations ranging from 0.39 to 0.55 were found between drinking times and dysphagia severity. In conclusion, liquids within the same IDDSI category can have different Bostwick flow rates and oral perception. The hypothesis that participants with OPMD may find certain liquids more challenging to swallow, despite being in the same IDDSI category, deserves further exploration in future studies.

Relationship between rheological properties, sensory perception, and overall acceptability of thickened liquids for dysphagia in young and old healthy individuals

This study investigated the relationship between rheological properties, sensory perception, and overall acceptability in healthy young and old groups for dysphagia thickened liquids. Unflavored (UTL) and flavored (FTLP) thickened liquids were prepared using tap water or pomegranate juice at 10 different viscosity levels. The rheological properties were then evaluated via syringe flow test and line spread test (LST). When the apparent viscosity levels of UTL and FTLP were similar, the syringe test and LST results were also similar, indicating consistent flow behavior. Sensory perception evaluations showed that the young group better distinguished viscosity differences between stages compared to the old group. Regarding overall acceptability, the old group preferred samples with higher apparent viscosity than the young group. Principal component analysis and k-means cluster analysis were used to explore correlations between variables and classify thickened liquids into four groups. This can serve the foundation for standardized texture grades of dysphagia thickened liquids, considering rheological characteristics and sensory profiles.

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

Because the viscosity of thickened beverages prepared with thickeners gradually changes before consumption, achieving their desired viscosity is important for managing dysphagia. This study aimed to investigate the viscosity changes of thickened beverages (water, orange juice, and milk) prepared with xanthan gum (XG)- and starch-based commercial thickeners over time using the syringe flow test (SFT) and line-spread test (LST). The LST values of beverages stabilized more quickly (≤1.5 h) than the SFT values (2.0∼3.5 h) at level 2 (mildly thick), whereas the opposite finding was observed at level 3 (moderately thick). After stabilization in a water system, SFT and LST yielded similar results. However, the SFT values of orange juice and milk thickened with XG-based thickener exceeded the reference values at level 2 and gradually increased at level 3. These results may be attributed to particulates interrupting fluid flow from the small tip of the syringe and the high friction force caused by the contact between the thickened sample and the syringe surface. The results suggest that the LST method is more reliable than the SFT method in clearly distinguishing between levels 2 and 3 of thickened beverages and demonstrate that the viscosity measurements of thickened beverages over time after preparation were strongly influenced by the measurement tools used for predicting the thickness level.

Factores limitantes del uso de las consistencias en la alimentación del paciente con disfagia: percepción del cuidador principal

Las acciones de abordaje del paciente con disfagia, al ser la disfagia de larga duración, exigen la participación directa y permanente del cuidador principal, que es, finalmente, quien define los procesos que se desencadenan desde casa para el cuidado de la alteración de ingesta. Bajo esta perspectiva, el cuidador del sujeto con disfagia sería quien debe estar capacitado de manera plena en los procesos de abordaje, no sólo como conocimiento de las técnicas utilizadas en la rehabilitación, sino también como forma de aprobación de su uso. Con el fin de describir la relación del cuidador principal en el uso y manejo de la modificación de consistencia, se plantea un proceso mixto de registro que permita evidenciar la percepción del cuidador hacia el uso de esta técnica. El trabajo evidencia como hallazgos aspectos limitantes que se concatenan con determinantes sociales de la salud y que, desde una mirada económica, de responsabilidad y de conocimiento del manejo de las consistencias, ubican a la disfagia en un lugar complicado de abordar para el cuidador, debido a las distintas realidades.

Effect of Intensive Oropharyngeal Training on Radiotherapy-Related Dysphagia in Nasopharyngeal Carcinoma Patients

OBJECTIVE

To evaluate the effect of intensive oropharyngeal functional training on swallowing in patients with dysphagia after radiotherapy for nasopharyngeal carcinoma.

METHODS

Fourteen patients with nasopharyngeal carcinomas and dysphagia after radiotherapy received intensive oropharyngeal training for two weeks. The Functional Oral Intake Scale (FOIS) and videofluoroscopic swallowing studies (VFSS) were used to evaluate swallowing function before and after intensive oropharyngeal training. Spatiotemporal parameters of the VFSS were analyzed using a digital image analysis system.

RESULTS

After training, the FOIS, Rosenbek penetration-aspiration score, DIGEST, normalized residue ratio scale, and spatiotemporal parameters of VFSS were significantly improved (P < 0.05).

CONCLUSIONS

This study indicated that intensive oropharyngeal training improves swallowing function after radiotherapy in patients with nasopharyngeal carcinoma.

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.

Recovery pattern analysis of swallowing function in patients undergoing total glossectomy and hemiglossectomy

OBJECTIVES

To investigate the recovery process of swallowing function and ascertain swallowing pattern in patients undergoing total glossectomy (TG).

MATERIALS AND METHODS

A cohort study was conducted in consecutive patients with tongue squamous cell carcinoma who received TG/hemiglossectomy (HG) from May 2017 to December 2019. Exposure factors included tongue resection range (HG and TG) and postoperative radiotherapy (PRT and non-PRT). The swallowing functions were evaluated by M.D. Anderson dysphagia inventory (MDADI), water swallow test (WST), and tongue pressure (TP) at pretreatment, 1, 4, 7, 12, 18 and 24 months postoperatively. Videofluoroscopy swallowing study (VFSS) was applied to analyze swallowing pattern of TG patients.

RESULTS

A total of 67 patients were enrolled, of which 17 underwent TG and 50 underwent HG. Both MDADI and TP of the TG and PRT group were lower than those of the HG and non-PRT group. TG patients had no evident improvement in MDADI and TP after surgery. There was a higher risk of swallowing unsafety with abnormal WST outcome in TG (P < 0.001, OR = 106.52) than that in HG. VFSS analysis identified prolonged oral and pharyngeal transit time, disorganized swallowing sequence, abnormal hyoid bone movement, and frequent invalid swallows in patients with TG. A shortened OTT (<5066.50 ms) and a larger pharyngeal constriction ratio (PCR > 0.31) were associated with increased risks of penetration and aspiration.

CONCLUSION

Postoperative swallowing pattern is a characteristic of severely impaired safety and efficacy in patients with TG. Impaired OTT and PCR are variables that should be examined when determining the need for rehabilitation treatment.

Bionic design of the oral swallowing in vitro and its application in the dysphagia

Dysphagia, the swallowing disorder, is a common disease among the elders and stroke patients. Therefore, based on the bionic swallowing device (BSD) in vitro of similar human-tongue motion during swallowing, the development of functional food is necessary to improve the food swallowing quality of the deglutition disorders patients. In this study, the tongue motion was thoroughly investigated by extracting the characteristic data, and appropriate mechanisms in vitro were adopted to replicate the motion of the tongue swallowing according to the normal swallowing oropharyngeal data. The application of the BSD was also investigated at different swallowing grades (SGs). The study results indicated that the tongue motion consisted of tongue root point (TRP) and several tongue motor points (TMPs). The cam-link and push-rod mechanisms showed ellipse lines for TRP motion and straight lines for TMPs, respectively. Higher correlation coefficients between the tongue trajectories in the oropharyngeal data and simulated curves of the combined mechanism were observed. The average correlation coefficients between the tongue trajectories of patients at five SGs and those of the BSD were 0.87, proving its effectiveness and potential application. Furthermore, the corn-paste experiments of the BSD showed that dysphagia at five SGs could be a suitable choice for certain food concentrations. This will provide valuable insight into developing more functional foods in vitro for high deglutition disorders.

Rheological Information of Pudding-Thick Liquids Prepared Using Commercial Food Thickeners Marketed in Korea for Dysphagic Patients According to the Manufacturers’ Guidelines

Food thickeners are commonly used to prepare thickened liquids for the management of dysphagia. The National Dysphagia Diet (NDD) thickness levels of thickened liquids prepared with commercial food thickeners are known to vary depending on the thickener type, recommended amount of thickener, thickener brand, and preparation instructions. Particularly, detailed preparation instructions must be provided by the manufacturers to achieve the correct thickness levels. However, the rheological information on product labels provided by manufacturers is typically not accurate. Here, various pudding-thick liquids were prepared by mixing commercial xanthan gum (XG)-based thickeners based on the manufacturers’ guidelines, and their rheological properties were characterized. Several thickened liquids prepared with four different XG-based thickeners (A-D) marketed in Korea did not meet the pudding-like criterion (> 1,750 mPa·s) based on the NDD guidelines. Significant differences in rheological parameter values (η_a,50, n, and G′) were also identified among the various thickened liquids. Only one thickener (thickener A) manufactured in Korea showed optimal results, which satisfied the pudding-thick viscosity range for various food liquids and also showed lower stickiness and enhanced bolus formation ability for easy and safe swallowing when compared to other thickeners (B, C, and D).

Psyllium (Plantago ovata Forsk) in frozen banana pulp: Influence on rheological, nutritional and sensory characteristics

A frozen banana pulp with functional properties was developed and characterized in this work. For this, 0 g, 3 g, 5 g and 7 g of psyllium in 100 g of banana pulp were added. The use of this fiber in industrialized products can contribute to the nutritional enrichment of the products and provide functional benefits already acknowledged, such as lowering LDL cholesterol, lowering blood glucose, increasing satiety and relieving constipation. According to the World Health Organization, vegetable consumption should be increased, as it reduces the risk of chronic diseases. The main purpose of this work was to incorporate psyllium in frozen banana pulp to develop a healthy product. The samples were evaluated through chemical analyses, rheological properties and sensory testing with Check-All-That-Apply questions (CATA). The addition of psyllium had a significant effect not only on the viscosity but also on the sensory and nutritional properties of the frozen banana pulp. This study indicated that the production of frozen banana pulp with psyllium is viable, as it has desirable nutritional and sensory characteristics which can contribute to the maintenance of health.

Institutionalized elderly are able to detect small viscosity variations in thickened water with gum-based thickeners: should texture classifications be reviewed?

BACKGROUND

The prevalence of dysphagia is very high in institutionalized elderly. Knowledge of the rheological and sensory characteristics of the various thickeners in elderly is limited, although it has been seen that there are differences between the rheological behaviors of gum-based thickeners with different composition. Moreover, we have not found sensory studies of viscosity in institutionalized elderly. Our hypothesis was that viscosity ranges established by the scientific societies, such as the National Dysphagia Diet Task Force (NDD), seem to be very wide and individuals might be able to detect small differences within the same texture range. The objectives of our study were 1) comparing the rheological characteristics of two commercial gum-based thickeners with different composition, dissolved in water under standard conditions, and 2) perform a sensory analysis (with both adults and institutionalized elderly) to detect different viscosities within the same texture (nectar and honey).

METHODS

Two commercial thickeners based on gums (NC and RC) were studied analyzing their viscosity in water with different concentrations (shear rate: 50 s^- 1; temperature: 22-25 °C). A sensory analysis involving 26 elderly and 29 adult controls was carried out to evaluate whether differences within nectar and honey textures among gum-based thickeners could be distinguished.

RESULTS

As the shear rate increases, viscosity decreases (non-Newtonian and pseudoplastic behavior). At the same concentration, each thickener produces a different viscosity (p < 0.05). Institutionalized elderly detected viscosity differences in nectar range of 49.9 (2.5) mPa·s (p < 0.05) and 102.2 (4.7) mPa·s (p < 0.0001). They also detected viscosity differences in honey texture range of 134.6 (9.7) mPa·s (p < 0.05) y 199.3 (9.2) mPa·s (p < 0.0001). Their caregivers also detected viscosity differences in both viscosity ranges (p < 0.0001) and with greater intensity than the elderly in honey texture (p: 0.016).

CONCLUSIONS

Our results suggest that the accepted viscosity ranges by NDD for the different textures might be too wide because institutionalized elderly and their caregivers are able to discern small differences in viscosity in nectar and honey textures. Gum-based thickeners with different composition showed differences in viscosity capacity, so they are not interchangeable.

Effects of the internal syringe shape on the International Dysphagia Diet Standardization Initiative flow test

The International Dysphagia Diet Standardization Initiative (IDDSI) proposed the flow test (FT) as a simple method for measuring the viscosity of thickened liquids. However, the FT specifies the use of a particular syringe type (BD-Slip), which is unfortunately not easily available in Japan. Therefore, the current study primarily aimed to investigate the effects of the internal syringe shape on IDDSI FT and identify the most suitable syringe available in Japan for xanthan gum-based thickened liquids. Accordingly, four syringes, namely, Luer slip tip, Luer-Lok tip, TERUMO, and NIPRO syringes, were used to examine FT value with water and nine different water viscosity levels. The correlation and systematic errors on residual FT values between the BD-Slip syringe and the other three syringes were analyzed. The two-dimensional internal shapes of the four syringes were measured using industrial computed tomography (CT) scanning. Based on the results of our FT, TERUMO had the smallest error range among the three syringes, without systematic errors. On a CT scan, three of five tip-shape parameters showed the smallest difference between BD-Slip and TERUMO syringe. Therefore, TERUMO had the smallest FT error range compared with that in BD-Slip tip syringe, indicating that TERUMO could be used as a substitute for BD-Slip when performing IDDSI FT with xanthan gum-based thickened water in Japan.

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

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 (η_a,50). Plots comparing η_a,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.

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.

Exploring Tools for Designing Dysphagia-Friendly Foods: A Review

Dysphagia is a medical condition that affects normal swallowing. To prevent the risk of aspiration or choking, thickened fluids and texture-modified foods have been used for dysphagia management with the goal of slowing down the flow of liquids and protecting the airway. This article summarizes the available information about the rheological and textural parameters, the characterization of the most-used thickeners and the application of alternative texture modification technologies that are crucial to developing safe dishes for people who suffer from swallowing difficulties. Regarding rheological and textural measurements, fundamental and empirical methods are described.

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.

Are Medication Swallowing Lubricants Suitable for Use in Dysphagia? Consistency, Viscosity, Texture, and Application of the International Dysphagia Diet Standardization Initiative (IDDSI) Framework

Medication lubricants are thick liquids or gels that are designed to aid swallowing of solid oral dosage forms. Tablets and capsules are placed within a spoonful of the product for swallowing. The aim of this study was to describe and compare commercially available medication lubricants in terms of textural suitability for patients with dysphagia. Twelve medication lubricants were characterised according to the International Dysphagia Diet Standardisation Initiative (IDDSI) framework. Apparent viscosity, yield stress, thickness consistency, and various texture features were compared. Gloup Forte was the only medication lubricant classified as IDDSI level 4 (pureed/extremely thick) at room (24 °C) temperature. Four other Gloup products were IDDSI level 3 (liquidised/moderately thick) at room temperature but testing at 4 °C or pouring from the container instead of using the pump dispenser resulted in classification as IDDSI level 4. The IDDSI Flow test would have classified MediSpend and Slo Tablets as IDDSI level 3, but their very low yield stress led to these fluids flowing too quickly through the prongs of a fork and so these were classified as <3. Severo was IDDSI level 2. Heyaxon and the two versions of Magic Jelly tested contained lumps, and Swallow Aid had exceptionally high viscosity, hardness, adhesiveness, and gumminess, classifying them as IDDSI Level 7 (“regular textures”) and therefore as unsuitable for people with dysphagia according to IDDSI. This study provides valuable information to help with the selection of a safe medication lubricant with appropriate thickness level suited to each individual with dysphagia.

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.

Standard Recipes for the Preparation of Thickened Barium Liquids Used in the Diagnosis of Dysphagia

Barium sulfate is commonly used to prepare contrast media for videofluorograpy. The flow characteristics of thickened liquids formulated for oropharyngeal imaging are known to be greatly affected by the addition of barium. In this study, thickened barium liquids were prepared by mixing a commercial xanthan gum (XG)-based thickener (Visco-up^®) at different concentrations (0.1%-3.0%) with barium powder (Baritop HD^®), and differences in the viscosity between thickened non-barium and thickened barium liquids were investigated. In addition, the thickness levels of thickened barium liquids, which are based on the National Dysphagia Diet (NDD) and International Dysphagia Diet Standardization Initiative (IDDSI) guidelines, were classified by measuring the viscosity (NDD) and gravity flow through a syringe (IDDSI) with 0.1%-3.0% thickener concentrations. The apparent viscosity (η_a,50) values of thickened barium liquids were much higher than those of thickened non-barium liquids, indicating that the addition of barium to the XG-based thickener resulted in further thickening. Standard recipes for preparing thickened barium liquids with desirable thickness levels were also established, showing the different thickener concentrations corresponding to the different NDD and IDDSI levels.