Effects of changing syringe driver height on flow: a small quantitative stud

Andrew I Donald, Meher P Chinthamuneedi, Douglas Spearritt

Intensive Care Unit, St Vincent’s Hospital, Toowoomba, QLD

Objective

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

Method

A bench experiment was performed to quantify the effect of height on pumps used in our own 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

Raising the pump 30 cm produced significant drug delivery boluses — up to seven times the programmed rate at 2 mL/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 noflow times of up to 180 seconds at 2 mL/h, again inversely proportional to the programmed rate.

Conclusions

Vertical displacement of a common syringe pump by 30cm produced significant bolus and cessation phenomena. These findings confirm the observations of previous authors and also demonstrate that significant flow irregularities occur 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