Measurement of compliance of infusion device consumable elements using an analytical weighing balance

The value of compliance of disposable elements such as infusion lines and syringes can significantly affect the performance characteristics of infusion devices. In a technique used to determine the compliance of infusion lines, the item under test is placed in a semi sealed water filled enclosure and the volume of fluid displaced is measured on an analytical weighing balance as set pressures are applied to the test item. Thermal drift of the measurement chamber was minimised by inclusion of discs of Invar alloy. Measurements were also made to determine the compliance of syringes used with syringe drivers where the volume of fluid displaced upon release of established pressure levels within a syringe was measured using a separate measurement configuration using again an analytical weighing balance. These techniques were used to determine the relative contributions to compliance of infusion lines and syringes to the dynamics of operation of syringe drivers. This indicated that contributions to compliance from syringes were significantly greater than that of connected infusion lines. Values of time to occlude, occlusion bolus and effects of height elevation for infusion devices with elements of varying compliance and line configuration are discussed.