Patent ID: 6497680
Filing Date: 2002-12-24
Classification: A61M,G05D

Abstract:
A pump employed to infuse a fluid flowing from a source into a patient, comprising:(a) a disposable cassette having a housing that defines a fluid path from an inlet port that is adapted to couple in fluid communication with the source, to an outlet port that is adapted to couple in fluid communication with an infusion site on the patient, said fluid path including: (i) a chamber covered by an elastomeric membrane that when forced into the chamber, displaces the fluid from the chamber through the outlet port, said chamber including a pressure sensor that produces a signal indicative of a pressure in the chamber (ii) an inlet valve controlling flow of the fluid into the chamber from the inlet port, said inlet valve being open as fluid flows into the chamber from the inlet port and closed as the fluid is displaced through the outlet port; and (iii) an outlet valve controlling flow of the fluid from the chamber toward the outlet port, said outlet valve being open when the fluid is displaced through the outlet port and closed as the fluid flows into the chamber from the inlet port; (b) a drive unit adapted to couple with disposable cassette and including at least one prime mover and a plunger, said at least one prime mover moving the plunger relative to the chamber to deform the elastomeric membrane, thereby displacing fluid from the chamber toward the outlet port, said drive unit also actuating the inlet valve and outlet valve to open and close said valves; and (c) a control unit, coupled to receive the signals from the pressure sensor, and coupled to the drive unit to control said at least one prime mover and thereby controlling movement of the plunger, said control unit determining a differential pressure from the signals produced by the pressure sensor and adjusting an initial position of the plunger relative to the chamber before the plunger displaces the fluid from the chamber, to compensate for the differential pressure, so that an accuracy of the pump in infusing the fluid into the patient is substantially improved.