High risk infusions-accuracy compromised by changes in patient venous pressure

Intensive care often requires the simultaneous administration of high potency short half-life intravenous drugs. Numerous reported instances of unwanted transient flow characteristics such as bolus flow, slow start-up at set rate and fluid reflux-where fluid is found to flow away from the infusion site-have indicated a need for better understanding of the system dynamic. This article introduces a simple mathematical model of an infusion pump system, highlighting system mechanical compliance as a major contributory factor for flow error. The model is verified as correctly predicting flow variation caused by pump height change and is offered as an aid in the development of more accurate infusion devices. The accurate delivery of low flow rates requires small volume rigid components. This study also suggests that the current design of syringe infusion devices makes them susceptible to flow error caused by change in patient venous pressure.