Influence of enteral nutrition viscosity on international dysphagia diet standardisation initiative classification, feeding tube, and pump infusion compatibility

Viscosity is an important physical property of enteral nutrition because it can affect administration through feeding tubes and infusion systems. This study evaluated viscosity, International Dysphagia Diet Standardisation Initiative (IDDSI) classification, and device performance across increasing caloric densities of a powdered enteral formula. A fiber-free powdered formula was prepared at 16 caloric densities (1.0–2.5 kcal/mL) at 25 °C. Viscosity was measured in six replicates per condition, and thickness was classified using the IDDSI syringe flow test. Gravity administration through 4–16 French (Fr) feeding tubes and pump infusion programmed at 100 mL/h were assessed. Viscosity was compared using one-way analysis of variance with Tukey’s post hoc test; Spearman correlation described the ordered concentration–viscosity relationship. Mean viscosity increased from 27.50 ± 1.03 to 347.83 ± 6.21 cP ( P < 0.0001), with IDDSI levels ranging from 0 to 3. Single documented 12 Fr collections at 1.5, 1.8, and 2.3 kcal/mL yielded approximately 125, 75, and 25 mL over 10 min, corresponding to average flow rates of 12.5, 7.5, and 2.5 mL/min. Approximate residual syringe volumes were recoverable for four concentrations, without replicate residual measurements. Pump mass differences were available for 1.0–1.9 kcal/mL (six observations per condition), with greater dispersion at 1.8–1.9 kcal/mL. Unsuccessful passage was reported qualitatively at ≥ 2.0 kcal/mL, without a quantitative mass series. Increasing caloric density was associated with higher viscosity and IDDSI level and with reduced gravity flow in the tested formula. The combined measurements identify changes relevant to enteral administration, while supporting formula- and device-specific assessment rather than a universal compatibility threshold.