An evaluation of methods of increasing the flow rate of i.v. fluid administration

I have evaluated in vitro methods of increasing the flow rate of clear fluids through an i.v. cannula at room temperature. These included, alone and in combination: increasing the height of a gravity-fed system; increasing the i.v. cannula diameter, manual compression of the lower drip chamber and the use of pressure bags. Flow rate was measured using a uroflowmeter, which was found to be reliable and reproducible. The most effective methods of increasing flow were the use of a 14-gauge cannula rather than a 16-gauge cannula, which resulted in a 50% increase, and the use of a 300-mm Hg pressure bag with automatic adjustable pressure regulator, which doubled the flow rate. The combination of these two tripled the overall flow to nearly 600 ml min-1. Manual compression of the drip chamber, despite producing peak pressures of more than 100 cm H2O, was an inefficient method of improving flow compared with an external pressure bag.