Effects of infusion tubing line lengths and syringe sizes on infusion system compliance: an experimental study using a syringe-type infusion pump at low flow rate

Ideally, the flow delivery of an infusion system is proportional only to the rate of mechanical actuation of the syringe pump plunger. However, in the real world, overall infusion system compliance may be affected by components such as an extension of tubing lines, or different sizes of syringes. With higher compliance, there may be greater chances of flow irregularity. In this experimental study, we investigated the effects of lengths of infusion lines and syringe sizes on the compliance of syringe pumps with low flow rate (2 ml h⁻¹). In the first experiment, infusion system compliance was measured in various settings by occlusion release. As the infusion tubing length and size of the syringe increased, the time to reach each pressure was delayed and the infusion system compliance increased. The contributions to system compliance from syringes were significantly greater compared to those of extended infusion lines. In the occlusion alarm experiment, the occlusion alarm could be delayed by 69.76 ± 3.98 min for the 50-ml syringe with a 560 cm infusion line set-up. In conclusion, the compliance of a syringe pump system increases as the loaded syringe size, or the length of the infusion tubing increases. The occlusion alarm may be much delayed and not useful in highly compliant systems with respect to the potential occlusion of the infusion system, so more attention is required when using a highly compliant infusion system.