Viscosity in Infant Dysphagia Management: Comparison of Viscosity of Thickened Liquids Used in Assessment and Thickened Liquids Used in Treatment

Abstract

The purpose of this study was to investigate comparability of viscosity of liquids used in assessment and treatment of infants with dysphagia. Goals of this study were as follows: (1) Establish baseline viscosity values for (a) the commercial barium assessment liquids of varying thicknesses and (b) clinically typical infant formula thickened with varied thickeners. (2) Compare the baseline viscosities of the various liquids for correlation of values. We attempted to mimic real-world situations and recreate clinical assessment and treatment conditions. We also identified and made every effort to control typical clinical variables, e.g., mixer and mixing procedure, brand of product, and temperature of liquid. The method of measurement was based on rheologic principles and used a Brookfield Engineering LVDV II + Pro Cone/Plate Viscometer at spindle and speed combinations to maximize shear rates consistent with swallowing. Statistically, there was no comparability between barium and formula mixtures, regardless of thickener utilized. The implications of these findings and the need to develop a standardized means of thickening formula to a viscosity comparable to the assessment materials are discussed.

Liquid Barium is not Representative of Infant Formula: Characterisation of Rheological and Material Properties

“…These previous studies suggested that liquids used in the test situation at an objective level are not representative of liquids used for nutrition and hydration. To date there is one study that has examined these discrepancies for infant VFSS [4]. Stuart and Motz [4] investigated the viscosity of regular (thin) formula (Enfamil LIPIL with Iron 20 cal/oz), thin barium (Lafayette Tonopaque powdered barium mixed with tap water to 40% w/w or 60% w/v), formula hand-thickened with rice/oat cereal and pulverised rice/oat cereal, formula hand-thickened with a commercial thickening agent (Simply Thick, xanthan gum), and commercially available thick barium (Varibar ''nectar,'' E-Z-EM Inc.).…”

“…To date there is one study that has examined these discrepancies for infant VFSS [4]. Stuart and Motz [4] investigated the viscosity of regular (thin) formula (Enfamil LIPIL with Iron 20 cal/oz), thin barium (Lafayette Tonopaque powdered barium mixed with tap water to 40% w/w or 60% w/v), formula hand-thickened with rice/oat cereal and pulverised rice/oat cereal, formula hand-thickened with a commercial thickening agent (Simply Thick, xanthan gum), and commercially available thick barium (Varibar ''nectar,'' E-Z-EM Inc.). The researchers examined liquids at 25°C, which equates well with room temperature, but is considerably cooler than body temperature (37°C).…”

“…To date, no studies have investigated the effect of cooling of infant formula on subsequent viscosity. Stuart and Motz [4] found that oat cereal mixes poorly with formula and that formula thickened with cereal showed much larger standard deviations in viscosity than formula thickened with a commercial thickener. The researchers showed that different thickening agents must be considered a notable source of variation.…”

“…Stuart and Motz [4] had difficulty with their viscometer such that they were unable to assess the thin liquid samples at the same shear rate as the thickened samples. The shear rate refers to the velocity/speed at which one layer of liquid flows over an adjacent parallel layer.…”

Pediatric Dysphagia: Physiology, Assessment, and Management

“…During this study, the patient is presented with barium-impregnated liquid and food, and videofluoroscopic monitoring is used to document oropharyngeal swallow function and swallowing disturbances [28]. Recent research studies have brought attention to the importance of having test fluids match prescribed fluids in terms of viscosity [29,30,31]. In addition, current literature suggests utilizing a pulse rate of at least 15 radiographic pulses per second for accurate interpretation of VFSS results [32].…”