Factors contributing to changes in viscosity and flow rate of a dedicated gel for gel immersion endoscopy

Abstract

Background and study aims Gel immersion endoscopy is a novel technique for securing the visual field during endoscopy. Clinical application of a dedicated gel for this technique with an appropriate viscosity to prevent mixing with blood and its efficacy was reported. The aim of this study was to evaluate changes in gel viscosity and flow rate under different conditions. Methods The viscosity of the gel after injection and flow rate were measured under various conditions changing the injection route and method. Gel viscosity was measured at 25, 10, and 4 °C. Results A decrease in gel viscosity was found when the gel was injected via the water jet channel compared to the accessory channel. The flow rate and decrease in viscosity of the gel injected via the water jet channel were 220 mL/min and 63.2 %, while when injected via the accessory channel with a clip device inserted were 560 mL/min and 35.8 %. When the gel was kept at a low temperature, the viscosity increased. Conclusions Gel injection via the accessory channel should be the first choice for efficient use considering the viscosity and flow rate.

Gel stored at low temperature maintains high viscosity even when injected via the water jet channel

“…VISCOCLEAR (Otsuka Pharmaceutical Factory, Tokushima, Japan), which is designed for gel immersion endoscopy, has the appropriate viscosity to prevent mixing with blood and/or residue immediately and facilitates securing the visual field during endoscopy [1]. Hiraki, et al reported that when gel stored at room temperature (25 °C) was injected via the water jet channel using a water pump at the maximum power setting, its viscosity significantly decreased to 321 mPa • s [2], which is close to 231 mPa • s, the lower limit of viscosity required for effectiveness [1]. Hiraki et al also reported that the viscosity of the gel, which was 768 mPa • s at 25 °C, increased to 998 mPa • s when stored at 4 °C [2].…”

“…Hiraki, et al reported that when gel stored at room temperature (25 °C) was injected via the water jet channel using a water pump at the maximum power setting, its viscosity significantly decreased to 321 mPa • s [2], which is close to 231 mPa • s, the lower limit of viscosity required for effectiveness [1]. Hiraki et al also reported that the viscosity of the gel, which was 768 mPa • s at 25 °C, increased to 998 mPa • s when stored at 4 °C [2].…”