Viscosity in infant dysphagia management: comparison of viscosity of thickened liquids used in assessment and thickened liquids used in treatment

Thickened liquids: do they still have a place in the paediatric dysphagia toolkit?

PURPOSE OF REVIEW

Use of thickened fluids has long been a cornerstone of dysphagia management. However, clinicians and researchers are increasingly questioning their effectiveness and highlighting potential harms. This review aims to present the current state of the evidence for use of thickened fluids in children.

RECENT FINDINGS

The relationship between aspiration and respiratory infection is complex. The role of thickened fluids in improving respiratory health is limited and contradictory. A high level of variability exists in all aspects of thickened fluid use. Little is known about patient and family perspectives on meaningful endpoints for intervention.

SUMMARY

Clinicians should be open and transparent in their decision making with patients and families, acknowledging the limited evidence and the need for individualised care. Further research is needed to establish the efficacy of thickened fluid use in children with regard to improvements in respiratory health, fluid intake and child and family wellbeing.

Frontline Interventions: Considerations for Modifying Fluids and Foods for Management of Feeding and Swallowing Disorders Across the Life Span

Purpose Individuals with dysphagia across the age continuum may require dietary modifications of fluids and foods for safe and adequate oral intake. Considerations of this frontline intervention are presented in this clinical forum dedicated to the discussion of dysphagia. Method This clinical focus article reviews the technical challenges of providing modified fluids and foods across the life span as well as the literature specific to its origins, efficacy, challenges and solutions to standardization, and the methods for ensuring quality service delivery. Conclusion Dietary modification is an often-used method of dysphagia management that presents unique challenges to the clinician for successful application. Speech-language pathologists in clinical practice across all settings must remain dedicated to evidence-based practice as they navigate service delivery of this strategy to individuals with dysphagia across the life span.

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.

Swallowing Analyses of Neonates and Infants in Breastfeeding and Bottle-feeding: Impact on Videofluoroscopy Swallow Studies

Introduction  Dysphagia, when left untreated, can result in an increase in morbidity and mortality rates, especially among infants with history of life-threatening neonatal diseases. The videofluoroscopy swallowing study (VFSS) is considered the gold standard for the diagnosis of dysphagia. There are few imaging studies of infant swallowing based on videofluoroscopy, none of which were performed during breast-feeding. Objective  To analyze the similarities and differences in infant swallowing function -regarding the feeding method - breast or bottle - and the impact on videofluoroscopy findings. Methods  A retrospective study of 25 VFSSs of breastfeeding and bottle-feeding infants was performed. The studied variables were: oral capture and control; tongue versus mandible movement coordination; sucking pattern; mandible excursion; liquid flow; bolus retention; laryngeal penetration; tracheal aspiration; clearing of material collected in the pharynx; and gastroesophageal reflux (GER). Results  The study showed a statistically significant association between nipple/areole capture; oral control; sucking pattern; mandibular excursion; liquid flow and feeding method. The velar sealing deficit, the place that trigger the pharyngeal swallow, food retention in the pharyngeal recesses, laryngeal penetration and GER were also factors associated with the feeding method. Conclusion  The analysis of the swallowing characteristics of both feeding methods revealed significant differences between them, with an impact on the diagnosis in the VFSSs, especially regarding velar function.

Modulation of Tongue Pressure According to Liquid Flow Properties in Healthy Swallowing

Purpose During swallowing, the tongue generates the primary propulsive forces that transport material through the oral cavity toward the pharynx. Previous literature suggests that higher tongue pressure amplitudes are generated for extremely thick liquids compared with thin liquids. The purpose of this study was to collect detailed information about the modulation of tongue pressure amplitude and timing across the range from thin to moderately thick liquids. Method Tongue pressure patterns were measured in 38 healthy adults (aged under 60 years) during swallowing with 4 levels of progressively thicker liquid consistency (International Dysphagia Diet Standardisation Initiative, Levels 0 = thin, 1 = slightly thick, 2 = mildly thick, and 3 = moderately thick). Stimuli with matching gravity flow (measured using the International Dysphagia Diet Standardisation Initiative Flow Test; Cichero et al., 2017 ; Hanson, 2016 ) were prepared both with/without barium (20% weight per volume concentration) and thickened with starch and xanthan gum thickeners. Results After controlling for variations in sip volume, thicker liquids were found to elicit significantly higher amplitudes of peak tongue pressure and a pattern of higher (i.e., steeper) pressure rise and decay slopes (change in pressure per unit time). Explorations across stimuli with similar flow but prepared with different thickeners and with/without barium revealed very few differences in tongue pressure, with the exception of significantly higher pressure amplitudes and rise slopes for nonbarium, starch-thickened slightly and mildly thick liquids. Conclusions There was no evidence that the addition of barium led to systematic differences in tongue pressure parameters across liquids with closely matched gravity flow. Additionally, no significant differences in tongue pressure parameters were found across thickening agents. Supplemental Material https://doi.org/10.23641/asha.7616537.

Use of Textured Thin Liquids in Patients With Dysphagia

PURPOSE

The goals of this article are to explore the use of textured thin liquids for dysphagic patients who require thickened liquids and to illustrate their impact on hydration and patient satisfaction.

METHOD

A retrospective evaluation of textured thin liquids was completed using patient data looking at laboratory values relevant to the detection of dehydration (blood urea nitrogen, creatinine, sodium) and patient satisfaction (using a clinician-generated questionnaire) on different modified liquid textures. In addition, the viscosity for all liquids was tested using a rheometer.

RESULTS

Measurements show that the viscosity of the textured thin liquids examined in this pilot study are significantly lower than the viscosity of nectar-thick liquids and fall within the "thin" category as defined by the National Dysphagia Diet guidelines. Patients on honey- and nectar-thick liquids had laboratory values signifying dehydration, whereas those receiving the textured thin liquid consistency were within the normal range for all laboratory values. Importantly, when consuming textured thin liquids, patients reported significant improvement in their satisfaction related to their thirst.

CONCLUSION

The results of this pilot study highlight the consequences of common thickened liquid dietary recommendations and of the potentially beneficial clinical application of textured thin liquids for patients with dysphagia as well as the need for future prospective research.

Short-Term Effects of Cold Liquids on the Pharyngeal Swallow in Preterm Infants with Dysphagia: A Pilot Study

Cold stimulation reduces airway compromise in adults with dysphagia. However, there is no sufficient evidence to support its use in the pediatric population. The primary goal of this pilot study is to assess the effect of cold liquid on the pharyngeal swallow mechanism in preterm infants with dysphagia. We hypothesized that thermal stimulation from cold liquid will decrease the risk of airway compromise in dysphagic preterm infants. Nine preterm infants with clinical symptoms of dysphagia were included. Video fluoroscopic swallow studies were used to assess the swallowing mechanism of each participant. The occurrence of swallow dysfunctions under room temperature liquid swallows (RTS) vs. short period cold liquid swallows (CS) was compared. Paired t test was used to test significance. The occurrence of deep penetration (p = 0.007) and aspiration (p = 0.002) decreased significantly in the CS condition compared with the RTS condition. There was a trend of less nasopharyngeal reflux with CS but did not reach statistical significance (p = 0.084). No differences were noted for mild penetration (p = 0.824). CS reduced airway compromise in dysphagic preterm infants compared to RTS. These data provide important information regarding the immediate effects of CS on pharyngeal swallowing in preterm infants with dysphagia. However, further investigation regarding its sustained effects is required before introducing to clinical practice.

Parent perception of the impact of using thickened fluids in children with dysphagia

BACKGROUND

Oropharyngeal dysphagia occurs in children without known neurological disorders, increasing their risk for respiratory problems and inadequate intake. Clinicians may recommend thickening nutritive fluids; however, there is little research regarding the impact of thickening nutritive fluids on clinical outcomes in children.

METHODS

We used a parental reporting tool to determine whether parents identified changes in signs of dysphagia or volume of intake when thickened fluids were incorporated into an individualized feeding program for dysphagic children without known neurological problems. Fifty-five children diagnosed with dysphagia, for whom thickened fluids had been recommended per radiographic and clinical exam, qualified for the study. Parents of 44 children (24 females, 20 males) aged 2 weeks to 14 months completed baseline and post-thickening (within 90 days) rating scales.

RESULTS

Compared to baseline, parents reported significant decreases in the frequency of apnea (W = -219, P < 0.0001, r = 0.399), congestion (W = -450, P < 0.0001, r = 0.579), coughing/choking with drinking (W = -485, P < 0.0001, r = 0.603), resistance to feeding (W = -344.5, P < 0.0001, r = 0.476), vomiting during feeding (W = -409, P < 0.0001, r = 0.565), and wheezing (W = -337, P < 0.001, r = 0.449). For those children whose parents initially reported inadequate levels of intake, there was a significant (Z = 3.15, P = 0.0029, r = 0.47) increase (+49.63 mm) in the rated adequacy of liquid intake, as well as a significant increase (+1.41 oz.) in the estimated volume per feeding (Z = 224, P = 0.29, r = 0.33).

CONCLUSION

These results provide information for clinicians and physicians to incorporate when considering the use of thickened fluids in the dysphagia management of children without a known neurological diagnosis.

Development of International Terminology and Definitions for Texture-Modified Foods and Thickened Fluids Used in Dysphagia Management: The IDDSI Framework

Dysphagia is estimated to affect ~8% of the world's population (~590 million people). Texture-modified foods and thickened drinks are commonly used to reduce the risks of choking and aspiration. The International Dysphagia Diet Standardisation Initiative (IDDSI) was founded with the goal of developing globally standardized terminology and definitions for texture-modified foods and liquids applicable to individuals with dysphagia of all ages, in all care settings, and all cultures. A multi-professional volunteer committee developed a dysphagia diet framework through systematic review and stakeholder consultation. First, a survey of existing national terminologies and current practice was conducted, receiving 2050 responses from 33 countries. Respondents included individuals with dysphagia; their caregivers; organizations supporting individuals with dysphagia; healthcare professionals; food service providers; researchers; and industry. The results revealed common use of 3-4 levels of food texture (54 different names) and ≥3 levels of liquid thickness (27 different names). Substantial support was expressed for international standardization. Next, a systematic review regarding the impact of food texture and liquid consistency on swallowing was completed. A meeting was then convened to review data from previous phases, and develop a draft framework. A further international stakeholder survey sought feedback to guide framework refinement; 3190 responses were received from 57 countries. The IDDSI Framework (released in November, 2015) involves a continuum of 8 levels (0-7) identified by numbers, text labels, color codes, definitions, and measurement methods. The IDDSI Framework is recommended for implementation throughout the world.

Understanding the Viscosity of Liquids used in Infant Dysphagia Management

When assessing swallowing in infants, it is critical to have confidence that the liquids presented during the swallow study closely replicate the viscosity of liquids in the infant's typical diet. However, we lack research on rheological properties of frequently used infant formulas or breastmilk, and various forms of barium contrast media used in swallow studies. The aim of the current study was to provide objective viscosity measurements for typical infant liquid diet options and barium contrast media. A TA-Instruments AR2000 Advanced Rheometer was used to measure the viscosity of five standard infant formulas, three barium products, and two breastmilk samples. Additionally, this study measured the viscosity of infant formulas and breastmilk when mixed with powdered barium contrast in a 20 % weight-to-volume (w/v) concentration. The study findings determined that standard infant formulas and the two breastmilk samples had low viscosities, at the lower end of the National Dysphagia Diet (NDD) thin liquid range. Two specialty formulas tested had much thicker viscosities, close to the lower boundary of the NDD nectar-thick liquid range. The study showed differences in viscosity between 60 % w/v barium products (Liquid E-Z-Paque(®) and E-Z-Paque(®) powder); the powdered product had a much lower viscosity, despite identical barium concentration. When E-Z-Paque(®) powdered barium was mixed in a 20 % w/v concentration using water, standard infant formulas, or breastmilk, the resulting viscosities were at the lower end of the NDD thin range and only slightly thicker than the non-barium comparator liquids. When E-Z-Paque(®) powdered barium was mixed in a 20 % w/v concentration with the two thicker specialty formulas (Enfamil AR 20 and 24 kcal), unexpected alterations in their original viscosity occurred. These findings highlight the clinical importance of objective measures of viscosity as well as objective data on how infant formulas or breastmilk may change in consistency when mixed with barium.

Effect of Bolus Viscosity on the Safety and Efficacy of Swallowing and the Kinematics of the Swallow Response in Patients with Oropharyngeal Dysphagia: White Paper by the European Society for Swallowing Disorders (ESSD)

BACKGROUND

Fluid thickening is a well-established management strategy for oropharyngeal dysphagia (OD). However, the effects of thickening agents on the physiology of impaired swallow responses are not fully understood, and there is no agreement on the degree of bolus thickening.

AIM

To review the literature and to produce a white paper of the European Society for Swallowing Disorders (ESSD) describing the evidence in the literature on the effect that bolus modification has upon the physiology, efficacy and safety of swallowing in adults with OD.

METHODS

A systematic search was performed using the electronic Pubmed and Embase databases. Articles in English available up to July 2015 were considered. The inclusion criteria swallowing studies on adults over 18 years of age; healthy people or patients with oropharyngeal dysphagia; bolus modification; effects of bolus modification on swallow safety (penetration/aspiration) and efficacy; and/or physiology and original articles written in English. The exclusion criteria consisted of oesophageal dysphagia and conference abstracts or presentations. The quality of the selected papers and the level of research evidence were assessed by standard quality assessments.

RESULTS

At the end of the selection process, 33 articles were considered. The quality of all included studies was assessed using systematic, reproducible, and quantitative tools (Kmet and NHMRC) concluding that all the selected articles reached a valid level of evidence. The literature search gathered data from various sources, ranging from double-blind randomised control trials to systematic reviews focused on changes occurring in swallowing physiology caused by thickened fluids. Main results suggest that increasing bolus viscosity (a) results in increased safety of swallowing, (b) also results in increased amounts of oral and/or pharyngeal residue which may result in post-swallow airway invasion, (c) impacts the physiology with increased lingual pressure patterns, no major changes in impaired airway protection mechanisms, and controversial effects on oral and pharyngeal transit time, hyoid displacements, onset of UOS opening and bolus velocity-with several articles suggesting the therapeutic effect of thickeners is also due to intrinsic bolus properties, (d) reduces palatability of thickened fluids and (e) correlates with increased risk of dehydration and decreased quality of life although the severity of dysphagia may be an confounding factor.

CONCLUSIONS

The ESSD concludes that there is evidence for increasing viscosity to reduce the risk of airway invasion and that it is a valid management strategy for OD. However, new thickening agents should be developed to avoid the negative effects of increasing viscosity on residue, palatability, and treatment compliance. New randomised controlled trials should establish the optimal viscosity level for each phenotype of dysphagic patients and descriptors, terminology and viscosity measurements must be standardised. This white paper is the first step towards the development of a clinical guideline on bolus modification for patients with oropharyngeal dysphagia.

Implications of changing the amount of thickener in thickened infant formula for infants with dysphagia

When a dysphagic infant is prescribed thickened infant formula (TIF) as a treatment method, some clinicians determine their own addition rates of thickener to meet the specific needs of the infant rather than relying on the directions on the tin. In this study the rheological behaviour of a TIF at different addition levels of thickener was measured to determine whether there was a difference in full rheological response and in viscosity. In addition, the time taken for the TIF to reach a near-stable viscosity was also measured. One hundred grams of Karicare® infant formula was made up according to the manufacturer’s instructions and Karicare® feed thickener was added at levels of 2, 3, 4, 5, and 6 g, respectively. A strain-controlled rheometer (ARES) with Couette geometry was used to rheologically characterise the TIF at the different levels of thickener addition. There was a significant difference in viscosity between the low levels and the higher levels of addition thickener (p < 0.05). Also, the low levels of thickener addition showed Newtonian-like behaviour, whereas the higher levels of addition were shear-thinning. The time taken for the thickener to reach a near-stable viscosity was found to be 10 min. Guidelines for thickened infant formula need to take into account the different levels of thickener addition rates.

Feed-Thickening Practices in NICUs in the Current Era: Variability in Prescription and Implementation Patterns

BACKGROUND

Feed-thickening for infants in the Neonatal Intensive Care Unit (NICU) is performed due to concerns of dysphagia and gastroesophageal reflux disease (GERD). No standards currently exist regarding feed-thickening prescriptions and practices and this results in variable and potentially unsafe feeding approaches.

METHODS

Electronic surveys were sent to neonatal feeding therapists and providers in order to determine the prescriptions and practices currently being used for feed-thickening in the NICU.

RESULTS

A total of 313 responses were collected. Results revealed the majority of providers use thickened feeds for concerns of dysphagia or GERD with some reporting they thicken expressed breast milk. Variability of thickening prescriptions was noted regarding consistencies, thickening agents, and recipes used. Reported approaches for measuring, mixing, and warming thickened feeds varied.

CONCLUSION

Variability was noted in the feed-thickening prescriptions and practices performed in the NICU. Further research and standardization are required to develop thickening guidelines.

Hard to swallow: Developmental biological insights into pediatric dysphagia

Pediatric dysphagia-feeding and swallowing difficulties that begin at birth, last throughout childhood, and continue into maturity--is one of the most common, least understood complications in children with developmental disorders. We argue that a major cause of pediatric dysphagia is altered hindbrain patterning during pre-natal development. Such changes can compromise craniofacial structures including oropharyngeal muscles and skeletal elements as well as motor and sensory circuits necessary for normal feeding and swallowing. Animal models of developmental disorders that include pediatric dysphagia in their phenotypic spectrum can provide mechanistic insight into pathogenesis of feeding and swallowing difficulties. A fairly common human genetic developmental disorder, DiGeorge/22q11.2 Deletion Syndrome (22q11DS) includes a substantial incidence of pediatric dysphagia in its phenotypic spectrum. Infant mice carrying a parallel deletion to 22q11DS patients have feeding and swallowing difficulties that approximate those seen in pediatric dysphagia. Altered hindbrain patterning, craniofacial malformations, and changes in cranial nerve growth prefigure these difficulties. Thus, in addition to craniofacial and pharyngeal anomalies that arise independently of altered neural development, pediatric dysphagia may result from disrupted hindbrain patterning and its impact on peripheral and central neural circuit development critical for feeding and swallowing. The mechanisms that disrupt hindbrain patterning and circuitry may provide a foundation to develop novel therapeutic approaches for improved clinical management of pediatric dysphagia.

Pediatric Dysphagia: Physiology, Assessment, and Management

Infancy and childhood represent a time of unparalleled physical growth and cognitive development. In order for infants and children to reach their linear and neurological growth potential, they must be able to reliably and safely consume sufficient energy and nutrients. Swallowing difficulties (dysphagia) in pediatric populations can have a detrimental effect on dietary intake and, thus, growth and development. As a result, it is imperative to accurately identify and appropriately manage dysphagia in pediatric populations. This article provides an overview of dysphagia in children, as well as common causes of childhood swallowing difficulties, populations at risk for pediatric dysphagia, techniques used to assess swallowing in pediatric patients, and the current treatment options available for infants and children with dysphagia.

Viscosidade e qualidade da imagem do líquido espessado para videodeofluoroscopia de deglutição com acréscimo do contraste de bário

OBJETIVOS: estudar a viscosidade da fórmula de partida espessada para os exames de videofluoroscopia de deglutição após acréscimo de contraste de Bário. MÉTODOS: copos de 200 ml de leite foram preparados em três consistências com sete espessantes. A viscosidade média foi verificada com viscosímetro nas temperaturas ambiente e acima de 40ºC, e após acrescentar o contraste de Bário em diluições a 50%, 25% e 12,5%. Os preparados foram expostos à fluoroscopia para obtenção de imagens que foram avaliadas quanto à visualização do preparado nas diferentes consistências, diluições e espessantes. RESULTADOS: comparando valores médios em centipoise(cP), observou-se que a viscosidade na consistência pudim foi significantemente menor na temperatura acima de 40ºC do que na temperatura ambiente. Nas consistências néctar e pudim o acréscimo de Bário resultou em mudança significante da viscosidade para mel. Não houve mudança na qualidade das imagens entre as diluições de Bário à 50% e 25%. CONCLUSÃO: o acréscimo do Bário resulta em mudanças nos valores de viscosidade que afetaram a consistência do preparado espessado para néctar e pudim. Uma redução da diluição do contraste para 25% não resulta em mudança clinicamente significante na qualidade da imagem. Os achados sugerem a importância da padronização do preparado para a fluoroscopia em relação à viscosidade e diluição do Bário visando garantir a reprodutibilidade do exame, prevenir falhas diagnósticas e otimizar as orientações para modificações da dieta na disfagia orofaríngea infantil.

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.

The Need for International Terminology and Definitions for Texture-Modified Foods and Thickened Liquids Used in Dysphagia Management: Foundations of a Global Initiative

Conservative estimates suggest that dysphagia (difficulty swallowing) affects approximately 8 % of the world's population. Dysphagia is associated with malnutrition, dehydration, chest infection and potentially death. While promising treatments are being developed to improve function, the modification of food texture and liquid thickness has become a cornerstone of dysphagia management. Foods are chopped, mashed or puréed to compensate for chewing difficulties or fatigue, improve swallowing safety and avoid asphyxiation. Liquids are typically thickened to slow their speed of transit through the oral and pharyngeal phases of swallowing, to avoid aspiration of material into the airway and improve transit to the esophagus. Food texture and liquid modification for dysphagia management occurs throughout the world. However, the names, the number of levels of modification and characteristics vary within and across countries. Multiple labels increase the risk to patient safety. National standardization of terminology and definitions has been promoted as a means to improve patient safety and inter-professional communication. This article documents the need for international standardized terminology and definitions for texture-modified foods and liquids for individuals with dysphagia. Furthermore, it documents the research plan and foundations of a global initiative dedicated to this purpose.

Matching the rheological properties of videofluoroscopic contrast agents and thickened liquid prescriptions

In the treatment of oropharyngeal dysphagia, the link between diagnosis and prescription of thickened liquids that are safe to swallow is not always straightforward. Frequently, the capacity to objectively assess and quantify the rheological properties of diagnostic test fluids and to select "rheologically equivalent" dietary products is missing. Perhaps sometimes the importance of an objective comparison is not fully appreciated because two liquids seem reasonably similar in a subjective comparison (e.g., flow from a spoon). The present study deals with some of these issues. Shear viscosity measurements were used to characterize the flow behavior of videofluoroscopic contrast agents and of thickened fluids prepared with commercial thickening agents. Effects of time and composition of the different fluids were analyzed regarding shear-rate-dependent viscosity. Nearly all materials tested showed a pronounced dependence of viscosity with shear rate ("shear thinning"). Results confirm that it is feasible (but not always straightforward) to "match" the viscosities of diagnostic fluids and thickened beverages if certain precautions are taken. For example, the time required to reach final viscosity levels can be significant for some thickeners, particularly when used with liquids containing contrast agents. It is recommend to use only diagnostic materials and thickening agents for which reliable viscosity data are available.

Preterm infant swallowing of thin and nectar-thick liquids: changes in lingual-palatal coordination and relation to bolus transit

Tongue-soft palate coordination and bolus head pharyngeal transit were studied by means of postacquisition kinematic analysis of videofluoroscopic swallowing images of ten preterm infants referred from hospital NICUs due to poor oral feeding and suspicion of aspiration. Sequences of coordinated tongue-soft palate movements and bolus transits during swallows of thin-consistency and nectar-thick-consistency barium were digitized, and time series data were used to calculate continuous relative phase, a measure of coordination. During swallows of nectar-thick compared to thin barium, tongue-soft palate coordination was more likely to be antiphase, bolus head pharyngeal transit time was longer, and coordination was significantly correlated with bolus head pharyngeal transit. Analysis of successive swallows indicated that tongue-soft palate coordination variability decreased with nectar-thick but not with thin-consistency barium. Together, the results suggest that slower-moving bolus transits may promote greater opportunity for available sensory information to be used to modulate timing of tongue-soft palate movements so that they are more effective for pumping liquids.

Addressing Nutrient Density in the Context of the Use of Thickened Liquids in Dysphagia Treatment

Thickening liquids has become a standard of practice for managing children with oropharyngeal dysphagia. A variety of commercial products have been developed from guar gum, xanthan gums, and modified corn starch. Practitioners and families are also trying to thicken liquids with available foods, such as infant rice cereal, yogurt, strained baby foods, and instant potato flakes. Throughout this process little consideration is given to the impact of the use of different thickeners on the nutrient density of human milk, formula, or other beverages. Various fluids were thickened by the author using different products to achieve National Dysphagia Diet nectar-like, or honey-like consistencies. Nutrient analysis of the calorie effect of the thickeners was calculated using the USDA Agriculture Research Service Nutrient database, manufacturer information, and displacement factors to evaluate the effects on calories per ounce of the thickened fluids. Considerations of thickener choice on other nutrients are discussed, including potential for toxicity of nutrient loads with specific thickeners. No one thickener is appropriate for all patients, but the characteristics of the various thickeners need to be understood. The assessment of the individual patient by an interdisciplinary team, including a registered dietitian should determine the patient’s specific needs before recommending a thickener.

Liquid barium is not representative of infant formula: characterisation of rheological and material properties

Infants experiencing dysphagia may undergo a videofluoroscopic swallow study (VFSS) to assess radiologically their coordination for sucking, swallowing, and breathing. No studies known to these authors have investigated whether the liquids used during infant radiological procedures are representative of liquids routinely fed to infants (e.g., formula). This study used an Advanced Rheometric Expansion System (ARES) strain-controlled rheometer to compare prethickened antiregurgitation formula, regular (thin) infant formula, and two types of regular infant formula, hand-thickened with a thickening agent and with liquid Polibar™ (barium-impregnated liquid). The viscosity, density, and yield stress of all samples were determined. Heated versus cooled liquids were compared. Results showed a significant difference in all rheological and material property parameters among the barium-impregnated liquids and the thickened and unthickened infant formula. This finding has important implications for the interpretation of the radiological results and subsequent clinical recommendations.