HYDRODYNAMIC EVALUATION OF INTRAVENOUS-INFUSION SYSTEMS

Study objective: We investigated the hydrodynamic characteristics of I V infusion sets for rapid fluid resuscitation. A simple technique has been devised for quantitative evaluation of the hydrodynamic character istics of IV sets, including their components, for a range of infusion pressures. Setting and methods: Previous investigations have measured the overall flow rate of infusion sets with and without IV catheters. This study presents a quantitative technique for measuring the resist ance to flow of the IV delivery set as a whole as well as its componen ts. An infusion set was measured with 14- and 18-gauge IV catheters wh ile delivering fluid at infusion pressures between 50 (gravity) and 40 0 mm Hg. Measurements and main results: At gravity-driven infusion, th e drip chamber imposes a resistance to flow of the same order as that of the catheter. At pressurized infusion with small-bore catheters, th e catheter consumes the majority of the overall pressure drop. At pres surized infusion with a large-bore catheter or tubing, the standard dr ip chamber becomes the limiting component and imposes the largest resi stance to flow. Conclusion: At gravity-delivered pressures (50 and 100 mm Hg), the only effective way of increasing flow rate (more than two fold) is to use a low-resistance drip chamber or to use two infusion s ites. At pressurized delivery pressures (more than 200 mm Hg), increas ing catheter size from 18 to 14 gauge would be more effective than dou bling the number of infusion sets. Also, a more efficient drip chamber adds an important advantage. Finally, increasing the tubing diameter adds only minimal benefit.