Fluid delivery control and monitoring apparatus for a medication infusion system

• US 4,919,596 A
• Filed: 04/26/1989
• Issued: 04/24/1990
• Est. Priority Date: 12/04/1987
• Status: Expired due to Term

• Current Assignee: Cardinal Health 303 Incorporated (Cardinal Health, Inc.)
• Original Assignee: Pacesetter Infusion, Ltd. (Siemens AG)
• Inventors: Henke, James L., Slate, John B.
• Primary Examiner(s): Smith, Leonard E.
• Assistant Examiner(s): Scheuermann, David W.
• Application Number:
  US07/344,494
• Time in Patent Office: 363 Days
• Field of Search: 417/63, 417/360, 417/362, 417/410, 417/415, 417/570, 417/479, 417/44, 417/45, 417/18, 604/65-67, 604/151-155, 128/DIG. 12, 128/DIG. 13, 128/DIG. 1
• US Class Current: 417/18
• CPC Class Codes: A61M 5/14216 Reciprocating piston type
• CPC Class Codes: A61M 5/16827 controlling delivery of multiple fluids, e.g. sequencing, mixing or via separate flow-paths infusion of multiple fluids without using a controller A61M5/1407
• CPC Class Codes: A61M 5/172 electrical or electronic A61M5/16804, A61M5/16831 take precedence
• CPC Class Codes: G05D 7/0688 by combined action on throttling means and flow sources G05D7/0694 takes precedence

Abstract

A fluid delivery monitoring and control apparatus for use in a medication infusion system is designed for use with a disposable fluid pathway that incorporates a sterile cassette containing pumping elements and sensor interfaces. The apparatus comprises a multi-segment drive mechanism, controller, and monitoring system. Fluid pumping is accomplished by controlling DC motors in the drive mechanism, each of which is coupled to two valves and a reciprocating piston for an individual pumping channel in the cassette. The motor is geared down to provide an appropriate maximum speed and torque. A cam sequentially actuates an inlet valve, piston, and an outlet valve in the cassette. A range of fluid delivery rates is achieved by periodically sending pulses to the motor. The output flow rate of the pump is maintained by a digital feedback controller which uses closed-loop feedback control to provide accurate regulation. At regular time intervals, the controller computes the motor voltage pulse width based upon feedback information from an encoder.

Claims

1. A fluid delivery monitoring and control apparatus for use in a medical infusion system employing a disposable fluid pathway and cassette, which cassette contains a plurality of fluid channels, each of which includes a positive displacement pump having a piston mounted for reciprocating movement within a chamber and respective intake and outlet valves for controlling fluid flow through said chamber, the apparatus comprising:

drive means for coupling to a cassette in association with a selected fluid channel including means for actuating said piston and said intake and outlet valves in a controlled sequence;

encoding means coupled to the drive means for providing signals indicative of home position and rate of movement of said drive means;

means for receiving rate command signals defining a desired rate of fluid flow through an associated cassette;

means for ascertaining fluid flow rate from rate of movement signals and from cassette indicia indicating piston stroke volume and generating feedback signals indicative of sensed flow rate; and

means for combining the rate command signals with said feedback signals to develop signals for controlling the drive means.

2. The apparatus of claim 1 further including control means coupled to receive said developed control signals including a pulse generator coupled to apply variable width drive pulses to said drive means and a pulse width controller coupled to control the pulse generator to generate drive pulses of a selected width corresponding to signals from the combining means.

3. The apparatus of claim 2 further including means to vary the amplitude level of said rive pulses between at least HIGH and LOW voltage levels in accordance with said rate command signals.

4. The apparatus of claim 3 further including means for selecting a HIGH voltage level for activating the drive means during movement of the piston to a home position.

5. The apparatus of claim 2 wherein the fluid flow rate ascertaining means comprise a pulse counter responsive to signals from the encoding means and means for inhibiting the pulse counter from counting pulses except when the cassette piston is delivering fluid through the outlet valve.

6. The apparatus of claim 2 wherein the encoding means further provide a logic signal distinguishing between delivery and non-delivery modes of the associated cassette fluid channel, the apparatus further including means for controlling the pulse generator to apply said variable width drive pulses to the drive means only during actuation in the delivery mode.

7. The apparatus of claim 6 wherein said pulse generator is coupled to activate said drive means continuously for a fill stroke interval which is within the duration of the non-delivery mode.

8. The apparatus of claim 1 wherein said controlled sequence consists of, beginning at a home position in which the inlet valve is open and the outlet valve is closed, actuating the piston through a fill stroke, closing the inlet valve, opening the outlet valve, actuating the piston in accordance with said developed signals through a delivery stroke, closing the outlet valve and opening the inlet valve.

9. The apparatus of claim 8 further including means for selectively braking said drive means.

10. The apparatus of claim 9 wherein said braking means is adapted to apply electronic braking to the drive means for a predetermined interval preceding actuation of said piston to deliver fluid for rates of fluid flow which are less than a selected threshold level.

11. The apparatus of claim 10 wherein the braking means is further adapted to apply electronic braking to the drive means upon receiving a signal indicative of home position from the encoding means.

12. The apparatus of claim 1 wherein said encoding means comprise a disk mounted to rotate with said drive means, said disk having a plurality of indicia located at selected points about its periphery for indicating rate of movement of the drive means.

13. The apparatus of claim 12 wherein said disk includes a fiducial mark indicative of home position.

14. The apparatus of claim 5 further including means for sampling the pulse counter at repetitive intervals and concurrently applying signals developed by the combining means to control the pulse generator at the same repetitive intervals.