A laboratory evaluation of resistive intravenous flow regulators

The clinical performance of four different resistive intravenous flow regulators was simulated in the laboratory. The devices tested were the Dial-A-Flo (DAF), Stat Master (SM), CorrectFlo (CFLO), and Arm-A-Flow (AAF). Five DAFs and five SMs were tested for accuracy at each of two flow settings. Accuracy is irrelevant for the CFLO and AAF, which have no metered dial. Flow rate for the DAF deviated from the 30-ml/hr setting by -25.1 +/- 7.2% (mean +/- SD) and from the 100 ml/hr setting by -23.4 +/- 3.5%. The SM deviation was -0.1 +/- 25.2% at a 10 ml/hr setting and -4.08 +/- 12.5% at the 100 ml/hr setting. Actual flow varied significantly with the individual DAF or SM unit employed. For all four devices, seven conditions of varying back pressure were modeled using different carrier flow rates and catheter clamps. Data from the DAFs, SMs, and CFLOs tested at the 100 ml/hr setting showed a linear relationship between flow rate and back pressure (r2 range, 0.82-0.88, P much less than 0.001). In contrast, AAF flow rate was relatively constant with changes in back pressure. We conclude that neither the DAF nor the SM metered dial provides accurate flow. The DAF, SM, and CFLO did not compensate for applied back pressure; the AAF did compensate for increasing back pressure, but was difficult to use. We cannot recommend any of the four brands tested for routine clinical use.