Effect of changes in syringe driver height on flow: a small quantitative study.

OBJECTIVE

To quantify flow irregularities in drug delivery caused by vertical displacement of syringe pumps.

METHODS

A bench experiment was performed to quantify the effect of height on pumps used in our intensive care and theatre settings. A standard syringe pump and line set loaded with a dye solution was run through a graduated length of tubing, and the effect of changing pump height quantified by measuring progress down the tubing over time.

RESULTS

A 30 cm elevation produced significant drug delivery boluses - up to seven times the programmed rate at 2mL/h. Delivery rate increased in inverse proportion to the programmed rate, as did the time taken to return to the programmed rate. Lowering the pump 30 cm resulted in no-flow times of up to 180 seconds at a flow rate of 2mL/h - again inversely proportional to programmed rate.

CONCLUSIONS

Vertical displacement of a common syringe pump by 30 cm produced significant bolus and cessation phenomena. These findings confirm the observations of previous authors and also demonstrate significant flow irregularities with smaller vertical displacements than previously tested. Further testing with other brands of pumps is required before a solution to this clinically important problem may be approached.