Apparatus for detecting fluid line occlusion

• US 5,103,211 A
• Filed: 11/06/1990
• Issued: 04/07/1992
• Est. Priority Date: 11/02/1989
• Status: Expired due to Term

• Current Assignee: Carefusion 303 Incorporated (Becton, Dickinson & Co)
• Original Assignee: Ivax Corporation (Teva Pharmaceutical Industries, Ltd.)
• Inventors: Everhart, Howard R., Daoud, Adib G., Horres, C. Russell Jr.
• Primary Examiner(s): Ng, Jin F.
• Assistant Examiner(s): Hofsass, Jeffery A.
• Application Number:
  US07/610,385
• Time in Patent Office: 518 Days
• Field of Search: 340/608, 340/603, 340/611, 417/63, 417/474, 417/479, 604/67, 128/DIG. 13
• US Class Current: 340/608
• CPC Class Codes: A61M 5/16859 Evaluation of pressure response, e.g. to an applied pulse
• CPC Class Codes: Y10S 128/13 Infusion monitoring

Abstract

An apparatus and method for detecting pressure and occlusion in a fluid line is for use with a fluid line being operated upon by a positive displacement, peristaltic pump having several cam follower fingers pressing against the fluid line fluid through the line peristaltically. A sensor follower finger is mounted to the cam shaft of the pump among the other peristaltic fingers in order to cyclicly press against the fluid line and displace the fluid line by a predetermined amount as the cam shaft rotates. The sensor follower finger includes a strain gauge mounted on the sensor finger to generate a signal indicating the degree of force being applied by the sensor finger against the tubing, and a signal processor which receives this force signal and determines the pressure within the fluid line based upon the signal. The signal processor determines the existence of an occlusion based on the signal and provides an alarm if an occlusion is determined.

Claims

1. An apparatus for measuring pressure within a compressible pumping segment of a fluid line having a flexible tubing wall, including a peristaltic pump mechanism for receiving said pumping segment, said peristaltic pump mechanism having a rotating camshaft and a plurality of cam follower fingers journalled thereto and including an upstream end cam follower finger and a downstream end cam follower finger adapted to sequentially press against said pumping segment producing cyclically recurring upstream and downstream pressure communication modes of a duty cycle of said pump mechanism in which a central portion of said pumping segment is alternately in communication with only an upstream portion of said fluid line and only a downstream portion of said fluid line, respectively, said apparatus comprising:

a sensor follower finger journalled to said camshaft adjacent said central portion of said pumping segment and intermediate said upstream end cam follower finger and said downstream end cam follower finger, and adapted to cyclically press against said pumping segment for a portion of said duty cycle with a predetermined displacement of said tubing wall without occluding said fluid line;

sensor means associated with said sensor follower finger for generating a force signal indicative of said force exerted by said sensor follower finger in pressing against said pumping segment; and

signal processing means responsive to said force signal for determining a measured pressure value based upon said force signal, for comparing said measured pressure with an upstream pressure threshold value in said upstream pressure communication mode and adapted to generate an upstream occlusion error signal when said measured pressure is less than said upstream pressure threshold value, and for subtracting said measured pressure in said downstream pressure communication mode from an upstream measured pressure to result in a difference pressure and adapted to generate a downstream occlusion error signal when said difference pressure is greater than a downstream pressure threshold value.

2. The apparatus of claim 1, further including alarm means for indicating an occlusion condition responsive to said upstream and downstream occlusion error signals.

3. The apparatus of claim 1, wherein said sensor follower finger has a tubing wall engaging end, a cam engaging end, and an intermediate pivot point therebetween, and said sensor means for generating the force signal comprises a strain gauge mounted on said sensor finger for measuring the force exerted by said sensor finger against said tubing wall.

4. The apparatus of claim 3, wherein said tubing wall engaging end includes an aperture, and said strain gauge is mounted to said sensor finger within said aperture.

5. The apparatus of claim 1 wherein the signal processor means is calibrated to the sensor means during the part of the cycle when the sensor follower finger is not in contact with the pumping segment.

6. The apparatus of claim 5 wherein the signal processor means is calibrated to the sensor means during each cycle of the sensor follower finger during the part of the cycle when the sensor follower finger is not in contact with the pumping segment.

7. The apparatus of claim 1 wherein the sensor means has a zero force value and the signal processor means is calibrated to this zero force value during the part of the cycle when the sensor follower finger is not in contact with the pumping segment.

8. The apparatus of claim 7 wherein the sensor means has a zero force value and the signal processor means is calibrated to this zero force value during each cycle of the sensor follower finger during the part of the cycle when the sensor follower finger is not in contact with the pumping segment.

9. A method for measuring pressure within a compressible pumping segment of a fluid line having a flexible tubing wall, said pumping segment being received in a peristaltic pump mechanism, said peristaltic pump mechanism having a rotating camshaft and a plurality of cam follower fingers journalled thereto and including an upstream end cam follower finger and a downstream end cam follower finger adapted to sequentially press against said pumping segment producing cyclically recurring upstream and downstream pressure communication modes of a duty cycle of said pump mechanism in which a central portion of said pumping segment is alternately in communication with only an upstream portion of said fluid line and only a downstream portion of said fluid line, respectively, comprising the steps of:

periodically compressing said pumping segment with at least one finger member with a predetermined amount of displacement of said flexible tubing wall without occluding said fluid line;

measuring a force parameter exerted by said finger member on said flexible tubing wall and generating a force signal indicating said measured force parameter; and

determining fluid pressure within said tubing responsive to said force signal.

10. The method of claim 9, wherein said pressure is determined from said force parameter, said amount of displacement, and a tube stiffness constant based upon the modulus of elasticity and thickness of the tubing wall.

11. The method of claim 9, wherein said displacement is in the range of from about 50 mils. to about 70 mils.

12. The method of claim 9 wherein:

the step of measuring a force parameter comprises applying a gauge to the at least one finger member to measure said force parameter; and

the step of determining fluid pressure comprises the step of calibrating the gauge during the part of the cycle when the at least one finger member is not compressing said tubing wall.

13. The method of claim 12 wherein the step of calibrating during the part of the cycle when the at least one finger member is not compressing said tubing wall comprising calibrating the gauge during each cycle.

14. The method of claim 9 wherein:

the step of measuring a force parameter comprises applying a gauge to the at least one finger member to measure said force parameter, said gauge having a zero force value; and

the step of determining fluid pressure comprises the step of calibrating to this zero force value during the part of the cycle when the at least one finger member is not compressing the tubing wall.

15. The method of claim 14 wherein the step of calibrating to the zero force value includes calibrating to the zero force value during each cycle of the sensor follower finger during the part of the cycle when the sensor follower finger is not compressing the pumping segment.

16. The method of claim 9 wherein said step of determining fluid pressure comprises:

determining upstream fluid pressure by receiving said measured force parameter during an upstream pressure communication mode;

determining downstream fluid pressure by receiving said measured force parameter during an upstream pressure communication mode and by receiving said measured force parameter during a downstream pressure communication mode and subtracting said upstream measured force parameter from said downstream measured force parameter.

17. The method of claim 16 further comprising the steps of:

comparing the upstream fluid pressure to a predetermined upstream pressure threshold and providing an occlusion signal in the event that the upstream fluid pressure is less than said threshold;

comparing the downstream fluid pressure to a predetermined downstream pressure threshold and providing an occlusion signal in the event that the downstream fluid pressure is greater than said threshold.

18. An apparatus for measuring pressure within a fluid line having a pumping segment with a flexible tubing wall, including a peristaltic pump mechanism for receiving said pumping segment, said peristaltic pump mechanism having a plurality of peristaltic fingers including an upstream end finger and a downstream end finger adapted to sequentially press against said pumping segment producing cyclically recurring upstream and downstream pressure communication modes of a duty cycle of said pump mechanism in which a portion of said pumping segment between said end fingers is alternately in communication with only an upstream portion of said fluid line and only a downstream portion of said fluid line respectively, said apparatus comprising:

a sensor follower finger disposed between said upstream end finger and said downstream end finger, adapted to cyclically press against said pumping segment for a portion of said duty cycle to displace the tubing wall of said segment by a predetermined amount;

a sensing gauge coupled to said sensor follower finger for generating a force signal indicative of the force exerted by said sensor follower finger in pressing against said tubing wall; and

a processor for receiving said force signal in said upstream pressure communication mode and for receiving said force signal in said downstream pressure communication mode and adapted to generate an occlusion signal based on the values of said force signals.

19. The apparatus of claim 18 wherein the processor is calibrated to the sensing gauge during the part of the cycle when the sensor follower finger is not in contact with the tubing wall.

20. The apparatus of claim 19 wherein the processor is calibrated to the sensing gauge during each cycle of the sensor follower finger during the part of the cycle when the sensor follower finger is not in contact with the tubing wall.

21. The apparatus of claim 18 wherein the gauge has a zero force value and the processor is calibrated to this zero force value during the part of the cycle when the sensor follower finger is not in contact with the tubing wall.

22. The apparatus of claim 21 wherein the gauge has a zero force value and the processor is calibrated to this zero force value during each cycle of the sensor follower finger during the part of the cycle when the sensor follower finger is not in contact with the tubing wall.

23. An apparatus for measuring pressure within a compressible pumping segment of a fluid line having a flexible tubing wall, including a peristaltic pump mechanism for receiving said pumping segment, said peristaltic pump mechanism having a rotating camshaft and a plurality of cam follower fingers journalled thereto and including an upstream end cam follower finger and a downstream end cam follower finger, said plurality of cam follower fingers adapted to sequentially press against said pumping segment producing cyclically recurring upstream and downstream pressure communication modes of a duty cycle of said pump mechanism in which a portion of said pumping segment disposed between said upstream end and downstream end cam follower fingers is alternately in communication with only an upstream portion of said fluid line and only a downstream portion of said fluid line, respectively, said apparatus comprising:

a sensor follower finger journalled to said camshaft adjacent said portion of said pumping segment and intermediate said upstream end cam follower finger and said downstream end cam follower finger, and adapted to cyclically press against said pumping segment for a portion of said duty cycle to displace said tubing wall by a predetermined amount;

sensor means associated with said sensor follower finger for generating a force signal indicative of said force exerted by said sensor follower finger in pressing against said pumping segment; and

a signal processor responsive to said force signal for determining a measured pressure value based upon said force signal, for comparing said measured pressure with an upstream pressure threshold value in said upstream pressure communication mode and adapted to generate an upstream occulsion error signal when said measured pressure is less than said upstream pressure threshold value, and for subtracting said measured pressure in said downstream pressure communication mode from an upstream measured pressure to result in a difference pressure and adapted to generate a downstream occlusion error signal when said difference pressure is greater than a downstream pressure threshold value.

24. The apparatus of claim 23 further including alarm means for indicating an occlusion condition responsive to said upstream and downstream occlusion error signals.

25. The apparatus of claim 23 wherein said sensor follower finger has a tubing wall engaging end, a cam engaging end, and an intermediate pivot point therebetween, and the sensor means comprises a strain gauge mounted on said sensor finger for measuring the force exerted by said sensor finger against said tubing wall.

26. The apparatus of claim 23 wherein the processor is calibrated to the sensor means during each cycle of the sensor follower finger during the part of the cycle when the sensor follower finger is not in contact with the tubing wall.

27. The apparatus of claim 25 wherein the gauge has a zero force value and the processor is calibrated to this zero force value during each cycle of the sensor follower finger during the part of the cycle when the sensor follower finger is not in contact with the tubing wall.

28. An apparatus for measuring pressure within a compressible pumping segment of a fluid line having a flexible tubing wall, including a peristaltic pump mechanism for receiving said pumping segment, said peristaltic pump mechanism having a rotating camshaft and a plurality of cam follower fingers journalled thereto and including an upstream end cam follower finger and a downstream end cam follower finger adapted to sequentially press against said pumping segment producing cyclically recurring upstream and downstream pressure communication modes of a duty cycle of said pump mechanism in which an intermediate portion of said pumping segment disposed between said upstream and downstream cam follower fingers is alternately in communication with only an upstream portion of said fluid line and only a downstream portion of said fluid line, said apparatus comprising:

a sensor follower finger journalled to said camshaft and adapted to cyclically press against said intermediate pumping segment for a portion of said duty cycle to displace said tubing wall by a predetermined amount;

sensor means associated with said sensor follower finger for generating a force signal indicative of said force exerted by said sensor follower finger in pressing against said pumping segment; and

a signal processor responsive to said force signal for determining a measured pressure value based upon said force signal; and

in said upstream pressure communication mode, for comparing said measured pressure value with an upstream pressure threshold value and adapted to generate an upstream occlusion error signal when said measured pressure is less than said upstream pressure threshold value; and

in said downstream pressure communication mode, for subtracting said upstream measured pressure value from said downstream measured pressure value and comparing said measured pressure difference with a downstream pressure reference value and adapted to generate a downstream occlusion error signal when said measured pressure is greater than said downstream pressure threshold value.

29. The apparatus of claim 28 further including alarm means for indicating an occlusion condition responsive to said upstream and downstream occlusion error signals.

30. The apparatus of claim 28 wherein said sensor follower finger has a tubing wall engaging end, a cam engaging end, and an intermediate pivot point therebetween, and the sensor means comprises a strain gauge mounted on said sensor finger for measuring the force exerted by said sensor finger against said tubing wall.

31. The apparatus of claim 28 wherein the processor is calibrated to the sensor means during each cycle of the sensor follower finger during the part of the cycle when the sensor follower finger is not in contact with the tubing wall.

32. The apparatus of claim 28 wherein the sensor means has a zero force value and the processor is calibrated to this zero force value during each cycle of the sensor follower finger during the part of the cycle when the sensor follower finger is not in contact with the tubing wall.