Viscosity study of maternal and formula milks according to the assessment proposed by the International Dysphagia Diet Standardisation Initiative Model: a comparison with Rheological Assessment.

Purpose: The present study aimed to investigate the behavior and the viscosity classification of liquids recommended for infants, up to six months, in Brazil, and their formulations used in Videofluoroscopy Swallowing Studies.

Methods: Breast milk from different gestational and breastfeeding time, two regular infant formulas, and one anti-reflux formula were evaluated in five different formulations: pure, mixed with liquid barium sulfate, in two proportions (20 and 33%), thickened with a specific thickener for neonates and thickened and mixed with 20% liquid barium sulfate, using the International Dysphagia Diet Standardisation Initiative model. The results were compared with data obtained from a previous rheological study.

Results: The breast milk samples and the infant formulas, in pure presentation, exhibited similar behavior except for the anti-reflux formula. The thickened samples with the addition of barium and the pure liquid barium sulfate exhibited the highest viscosity among the formulations. The increase in viscosity with the addition of barium occurred for all samples and for the thickened formulations, but not in linear behavior. The results showed minor differences of IDDSI classification compared to the findings obtained in the rheological study.

Conclusion: The present study revealed the variability of liquid viscosity across different formulations, supporting the idea of the importance of this knowledge in videofluoroscopic assessment. It has also highlighted the risk associated with using a subjective method in preparing the stimuli offered, allowing for greater reliability in diagnosing swallowing dynamics in neonates and infants. This approach may help prevent inaccurate diagnoses and harmful interventions.