Line spread as a visual clinical tool for thickened liquids

Improved system for measuring rheological properties of thickened liquid using an inclined parallel plate and optical sensor

The purpose of this study was to improve the method of using an inclined parallel plate (IPP) in directly estimating the yield stressτ iy and evaluating the properties of a thickened liquid. The flow curve of the relationship between the shear rate and shear stress of a liquid thickened with a xanthan gum agent was predicted using the Herschel-Bulkley fluid model ( τ = τ y + k γ ˙ n - 1 ). We supposed that the yield stressτ y and the result of a line spread test (LST) indicate the deformation state and the flow state of shear stress ( k γ ˙ n - 1 ), respectively.τ iy , the yield stressτ ry estimated adopting a rotational viscometer and LST, was investigated for three liquids thickened with xanthan gum at four concentrations (C) at intervals of 0.5 wt% within the range 0.5-2.0 wt%. Linear plots of the relations of C versusτ iy andτ ry and the LST show that with an increase in C , the resistance force (τ ry andτ iy ) increases until flow starts, after which viscosity increases. We suggest that yield stressτ iy estimated with the IPP method effectively indicates the rheological properties of thickened liquids.

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.

Sensory Profiling and External Preference Mapping of Pre-Thickened Water Products for Dysphagia

Dysphagia is a dysfunction of the swallowing system and thickened beverages are widely prescribed as a treatment. The objective of this study was to determine the sensory characteristics of pre-thickened water products and determine sensory drivers of liking for those types of products. Pre-thickened water products (two starch-based and two gum-based) were tested in both nectar and honey thick versions. Based on product availability, one product was neutral water, and the others were water with lemon flavoring added. The sensory characteristics of the products were evaluated with a highly trained descriptive panel, and the viscosity of the products was evaluated with both the Bostwick consistometer and the line spread test. Previously published consumer data was used to determine preference maps with the descriptive data. All lemon-flavored products had similar flavor characteristics, except the Thick & Easy Clear that had a less lemon-related flavor than the others. After excluding the lemon-related flavor characteristics, all pre-thickened products had similar “base flavor” notes, no matter whether the products were starch-based or gum-based. This contrasts with literature, which reports differences in flavor of thickened beverages prepared using thickening agents. The thickness of the products varied between nectar and honey thickness, but also varied among products that were stated to be at the same level of thickness. External preference mapping showed that both lemon-related flavor and a thinner beverage texture are potential drivers of consumers acceptance of the product, which was expected based on other studies. In conclusion, pre-thickened beverages are good alternatives for self-mixed thickening agents but a standard for thickness should be agreed on and used by manufacturers.

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.

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.

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.

The photographic atlas of Spanish food consistency: a new tool for the treatment of dysphagia

INTRODUCTION

dysphagia requires texture-modified foods and thickened liquids, which is difficult to explain to patients and caregivers.

METHODS

an atlas has been developed and validated to explain the consistencies using the Likert scale questionnaire and the Delphi survey. The agreement and reliability of the tool were evaluated, with a minimum of 80%. The atlas was developed in Spanish.

RESULTS

an agreement of 93.3% (95% CI: 63.7-100%) was obtained during the evaluation and a value of 97.5% and a Kappa index of 0.96 (95% CI: 0.93-0.99; p = 0.016] were obtained during the validation processes.

CONCLUSION

the atlas is a new valid tool that can be used by health professionals.

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

PURPOSE OF REVIEW

The use of thickened liquids has become one of the most common management strategies for individuals with dysphagia. The purpose of this paper is to review methods that can be used to measure the flow characteristics of liquids used in dysphagia management. We describe the measurement of apparent viscosity, measures of extensional flow, slump tests (specifically the line-spread test and Bostwick consistometry), gravity flow tests, and subjective methods.

RECENT FINDINGS

We discuss the relationship between different approaches to measuring flow, the 2002 American National Dysphagia Diet and the 2017 International Dysphagia Diet Standardisation Initiative (IDDSI) framework. A comparison of test results across four methods is provided.

SUMMARY

A consistent approach is needed for the measurement of flow for thickened liquids used in dysphagia management. This review highlights differences that can be expected across different flow testing methodologies. Adherence to a common method and measurement definitions will promote patient safety and facilitate future research regarding the effectiveness of texture modification as an intervention for dysphagia.

Comparison of two methods to categorize thickened liquids for dysphagia management in a clinical care setting context: The Bostwick consistometer and the IDDSI Flow Test. Are we talking about the same concept?

The Bostwick consistometer and the International Dysphagia Diet Standardization Initiative (IDDSI) Flow Test are both proposed methods to measure and categorize thickened liquids for dysphagia management. The objectives were to: (a) compare the Bostwick consistometer reference values used in clinical settings and the IDDSI reference values of thickened liquids suggested for nutrition care plans in the management of dysphagia when measuring commercially available preprepared thickened liquids; (b) explore the relationship between the two methods; (c) assess the interchangeability; (d) document the intra-rater reliability. Preprepared thickened liquids (n = 32) were measured twice with the Bostwick consistometer and 3 times with the IDDSI Flow Test, using a rigorous methodology. A registered dietitian nutritionist and a registered nutrition and dietetic technician performed the measurements. The Pearson's correlation coefficient was calculated to explore the relationship between the two methods. Using a linear regression equation, back-calculations of the IDDSI Flow Test values were done, based on the experimental Bostwick results. Interchangeability was assessed by documenting the level of agreement between the results with a Bland and Altman graphical analysis. Intraclass correlation coefficients calculation and a Bland and Altman graphical analysis were performed to assess reliability. The strong correlation (r = -.93, p < .001) between the IDDSI Flow Test and the Bostwick consistometer measurements suggests that they measure flow rate in a similar manner, but not exactly the same, as confirmed with the Bland and Altman graphical analysis. Thus, they produced results that are not interchangeable. However, both tests show excellent intra-rater reliability (ICC ≥ 0.99) when using a rigorous methodology. PRACTICAL APPLICATIONS: Thickened liquids are used to manage oropharyngeal dysphagia. Clinicians need to provide quality assurance/quality control (QA/QC) support in the selection or production of thickened liquids as well as staff training or patient education regarding these products. Methods and classification have been proposed to measure and categorize thickened liquids for dysphagia management, such as the line spread test, the Bostwick consistometer method, and the IDDSI Flow Test. Although empirical, these methods are more accessible to clinicians than viscometer or rheometer assessments. Clinicians need to understand the limitations of these techniques as neither appear to capture the full extent of consistency for potential beverages available on the market or produced in-house. In this article, we compare the Bostwick consistometer and the IDDSI Flow Test methods and classifications and propose a standard operating procedure in order to maximize the quality of results. We point out the large variations in consistency levels of commercial preprepared thickened liquids in light of the absence of evidence of clinical outcomes associated with either proposed methods or consistency classifications.

Visualizing the Consistency of Thickened Liquids With Simple Tools: Implications for Clinical Practice

PURPOSE

Accurate texture modifications to thin liquids are a critical aspect of patients' nutritional health and well-being. This study explored the use of 3 tools (2 distance- and 1 time-measuring devices) to characterize texture-modified liquids. The objectives were to use the tools to measure modified liquids, to determine if measurements differentiated nectar and honey levels of modification, and to compare measurements with other published reports.

METHOD

We measured the flow distance of 33 prethickened water samples in centimeters (cm) using a line spread apparatus and a Bostwick Consistometer (Christison Particle Technologies). We selected a Zahn viscosity cup to measure the stream time of each prethickened liquid in seconds.

RESULTS

The 2 distance-measuring devices (line spread and Bostwick Consistometer) showed that thinner (nectar-thick) modifications spread or flowed a farther distance in comparison to thicker (honey-like) modifications. Testing with the line spread indicated that an average spread distance of 4.5 cm differentiated nectar-thick and honey-like consistencies. A flow distance of greater than 15 cm differentiated nectar from honey consistency measured with a Bostwick Consistometer. We were not successful in using the Zahn viscosity cup to determine the stream time of modified liquids.

CONCLUSIONS

Two of the tools provided objective information about levels of liquid modification, which has implications for day-to-day preparation. Measurement tools that are accurate and easy to use have the potential to provide quick and dependable feedback to verify a prescribed level of liquid modification. Further efforts are needed to standardize the application of simple measurement tools in the management of patients who consume thickened liquids.

A review of diet standardization and bolus rheology in the management of dysphagia

PURPOSE OF REVIEW

Texture modification is a widespread practice as a strategy for the management of dysphagia and can be very effective in individual cases. However, it is often performed in a qualitative, subjective manner and practices vary internationally according to multiple sets of national guidelines. This article aims to identify best practice by reviewing the theory and practice of texture modification, focussing on recent advances.

RECENT FINDINGS

Instrumental assessment of texture modification in vivo is challenging, and studies including rheology and perception have indicated that fluid viscosity is only one of many factors affecting texture modification in practice. Systematic reviews have identified a historical lack of high-quality clinical evidence, but recent controlled studies are beginning to identify positive and negative aspects of thickened fluids. Research and practice to date have been limited by the lack of control and standardization of foods and drinks. However in 2015 a not-for-profit organization, the International Dysphagia Diet Standardisation Initiative, has published a framework for texture modification from thin liquids to solid foods based on all the existing documentation and guidance, and the - limited - available clinical evidence.

SUMMARY

Rheology exists in the lab; however, normal practice is often subjective or lacking control and standardization. In the near future, cohesion of practice and the availability of practical standardization tools may increase awareness and use of rheology.

Use of Thickened Liquids to Manage Feeding Difficulties in Infants: A Pilot Survey of Practice Patterns in Canadian Pediatric Centers

Improved survival rates of sick or preterm infants have resulted in an increase of observed feeding difficulties. One common method for managing feeding difficulties in infants is to manipulate liquid viscosity by adding thickening agents to formula or expressed breast milk. Concerns regarding the lack of clinical practice guidelines for the use of this strategy have been raised in the literature and in clinical settings for several years. This study aimed to survey feeding clinicians working in major Canadian pediatric centers to identify current practice patterns for use of thickened liquids in managing feeding difficulties of infants and to justify the need for standardization of this practice. A web-based pilot survey was developed using Fluidsurveys software. The questionnaire contained 37 questions targeting the process of prescribing thickeners, choice of thickener, awareness of issues, and inconsistencies raised in the literature about thickener use and how to address them. A total of 69 questionnaire responses were analyzed using descriptive statistics and inductive thematic analysis methods. Our study results indicate that thickened liquids continue to be broadly used to manage feeding difficulties in Canadian infants, despite numerous areas of concern related to their use raised by our respondents. While clear practice patterns for assessment and management were observed among the respondents, some areas of practice did not reflect recent published research or experts' opinion. Further research to develop a systematic approach for assessment, intervention, and follow-up is warranted to guide clinicians in this complex decision-making process.