Hydrodynamic evaluation of intravenous infusion systems.

STUDY OBJECTIVE

We investigated the hydrodynamic characteristics of IV infusion sets for rapid fluid resuscitation. A simple technique has been devised for quantitative evaluation of the hydrodynamic characteristics 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 resistance to flow of the IV delivery set as a whole as well as its components. An infusion set was measured with 14- and 18-gauge IV catheters while delivering fluid at infusion pressures between 50 (gravity) and 400 mm Hg.

MEASUREMENTS AND MAIN RESULTS

At gravity-driven infusion, the drip chamber imposes a resistance to flow of the same order as that of the catheter. At pressurized infusion with small-bore catheters, the catheter consumes the majority of the overall pressure drop. At pressurized infusion with a large-bore catheter or tubing, the standard drip chamber becomes the limiting component and imposes the largest resistance to flow.

CONCLUSION

At gravity-delivered pressures (50 and 100 mm Hg), the only effective way of increasing flow rate (more than twofold) is to use a low-resistance drip chamber or to use two infusion sites. At pressurized delivery pressures (more than 200 mm Hg), increasing catheter size from 18 to 14 gauge would be more effective than doubling the number of infusion sets. Also, a more efficient drip chamber adds an important advantage. Finally, increasing the tubing diameter adds only minimal benefit.