Regarding neonates and infants, the videofluoroscopy swallowing study is always conducted with liquids impregnated with a radiopaque material in varied proportions and thickenings. Variations in thickening and barium concentration are known to change the swallowing function. The present study aimed to analyze the rheological and macroscopic properties of barium contrast and liquids commonly used in Brazil with infants under six months old. This study was approved by the Ethics Committee under certificate number 63361616.2.0000.5482. Rheological measurements were performed on samples of breast milk and infant formulas, pure, with thickener, impregnated with liquid barium sulfate, as well as a pure barium sulfate sample. The data collected showed similar viscosity rates between breast milk and the infant formulas Aptamil and Enfamil. Impregnating them with 20% and 33% liquid barium sulfate increased their viscosity. However, they remained in the same classification, despite the quantitative differences in their apparent viscosity. The regular products, in formulation with thickener and thickener plus 20% barium, showed an increase in apparent viscosity close or twice to that of Enfamil A.R. impregnated with 33% barium sulfate. The study allowed a more in-depth understanding of how the products behave at strain rates consistent with the conditions when swallowing. The results indicated in this study confirm the need for knowledge and care in preparing liquids to be offered in videofluoroscopy swallowing studies with neonates and infants. They also emphasize the importance of objectively measuring the viscosities of videofluoroscopic fluids, matching them with the liquids to be prescribed in their diets.

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