Electronic Flow Rate Controller for a Portable Insulin Infusion Pump

An electronic controller is described that regulates the flow of infusate by controlling the fraction of time that a pump is energized. Using the integral programming capability of the device, any one of 256 possible basal rates between 0 and 49.6% of the maximum rate can be chosen. An externally triggerable single meal-associated pulse can also be configured. The rate during the meal pulse can be any one of the 255 equally spaced rates in the range of 0–99.7%. The duration of this pulse can be chosen in 3-min steps to a maximum of 12.75 h, after which the rate automatically returns to the basal value. The controller consumes a minimum amount of power and can continuously operate a dc motor-driven pump at 3.0 V for 36 h. It drives the pump in an on-off mode in order to control the average flow rate digitally. In this way a significant reduction in the power requirements is realized and the system can be run for many days using small rechargeable batteries. One year of experience with 20 of these controllers was obtained in the research laboratory and clinical investigation unit. The results of this experience indicated the reliability and precision of these controllers, gave insight into their modes of failure, and provided valuable biomedical data for their improvement.