Monitoring of the pressure of a product fluid to be administered in dosed amounts during infusion or injection

• US 6,368,314 B1
• Filed: 09/07/1999
• Issued: 04/09/2002
• Est. Priority Date: 09/08/1998
• Status: Expired due to Term

• Current Assignee: Roche Diabetes Care Inc. (Roche Holding AG)
• Original Assignee: Disetronic Licensing Ag
• Inventors: Kipfer, Urs, Imhof, Erich
• Primary Examiner(s): Sykes, Angela D.
• Assistant Examiner(s): THISSELL, JEREMY
• Application Number:
  US09/391,330
• Time in Patent Office: 945 Days
• Field of Search: 604/236, 604/237, 604/67, 604/65, 604/500, 604/506, 604/224, 604/225, 222/630, 222/390, 222/631, 222/336, 222/309, 222/333, 222/52, 222/396
• US Class Current: 604/506
• CPC Class Codes: A61M 2005/1402 Priming
• CPC Class Codes: A61M 2005/16863 Occlusion detection
• CPC Class Codes: A61M 2205/332 Force measuring means
• CPC Class Codes: A61M 5/14546 Front-loading type injectors
• CPC Class Codes: A61M 5/14566 with a replaceable reservoir for receiving a piston rod of the pump
• CPC Class Codes: A61M 5/16854 by monitoring line pressure

Abstract

The invention relates to a process for the monitoring of the pressure of a product fluid to be administered in dosed amounts during an infusion or injection, which is dispensable from a container that is received in or formed by a housing, by advancement of a piston received in the container. The reaction force exerted by the piston onto the housing, which serves as a measure for the fluid pressure, is hereby measured and fed to a control for a drive of the piston. The control compares the measured reaction force with a predetermined reference force and controls the drive of the motor under consideration of the result of the comparison. The reference force is a nominal value for the reaction force and a direct nominal/actual comparison is carried out between the measured reaction force and its nominal value. The invention further relates to an apparatus which is especially suited for carrying out the process.

Claims

1. Process for the monitoring of the pressure of a product fluid to be administered in dosed amounts during an infusion or injection, said product fluid being dispensable from a container (2), which is received in a housing (1) or formed by the latter, through advancement of a piston (6) received in the container (2), wherein

a) a reaction force exerted by the piston (6) onto the housing (1), which serves as a measure for the pressure, is measured and fed to a control (20) for a drive (7 to 11) of the piston (6) and

b) the control (20) compares the measured reaction force with a predetermined reference force and controls the drive (7 to 11) of the piston (6) under consideration of the result of the comparison, characterized in that

c) the reference force is a nominal value (S;

S′

) for the reaction force and a direct nominal/actual comparison is carried out between the measured reaction force and its nominal value (S;

S′

).

2. Process according to claim 1, characterized in that the nominal value (S′

) relied upon for the comparison with the measured reaction force is determined by measuring during a priming of the piston (6), in which the piston (6) is displaced from an installation position in the container (2) up to an expulsion of product fluid in a starting position for a first administration.

3. Process according to claim 2, characterized in that the reaction force measured during priming is compared with a predetermined standard nominal value (S) and upon compliance with a predetermined, maximum permissible difference to the standard nominal value (S) is used as new nominal value (S′

) during the administration.

4. Process according to claim 1, characterized in that a defined pressure drop (PV) is produced in a flow cross section of the product fluid between the container (2) and an infusion or injection needle (5).

5. Process according to claim 1, characterized in that during a priming of the piston (6), in which the piston (6) is advanced from an installation position in the container (2) until an expulsion of product fluid in a starting position for a first administration, a first striking of the drive (7 to 11) against the piston (6) is detected and the fill condition of the container (2) is determined from the position of the drive (7 to 11) upon contact.

6. Process according to claim 1, characterized in that a start-stop-frequency of a step motor (11) of the drive (7 to 11) is adjusted such that the step motor (11) is arrested upon a first contact of the drive (7 to 11) on the piston (6) and that a fill condition of the container (2) is determined from a position of the motor (11) held upon striking.

7. Process according to claim 1, characterized in that at least a first nominal value and a second nominal value for the reaction force are predetermined wherein the first nominal value represents a reaction force to be exerted for a displacement of the piston (6) from an at rest position and the second nominal value represents a reaction force which adopts a constant value during the displacement movement of the piston (6).

8. Apparatus for the monitoring of the pressure of a product fluid which is dispensable in dosed amounts for the purpose of an infusion or injection from a container (2) by advancement of a piston (6) received in the container (2), wherein the apparatus comprises:

a) a housing (1) receiving the container (2) or forming the latter,

b) a force sensor (13) which measures a reaction force serving as a measure of the pressure and exerted by the piston (6) onto the housing (1) and outputs it as a measured value, and

c) a control (20) which compares the measured value with a predetermined reference value and controls a drive (7 to 11) for the piston (6) under consideration of the result of the comparison, characterized in that,

d) at least one nominal value (S;

S′

) for the reaction force is stored in a memory (22, 23) of the control (20) and used for a direct nominal/actual comparison with the measured reaction force.

9. Apparatus according to claim 8, characterized in that a standard nominal value (S) for the reaction force is stored in a first memory (22) of the control (20), the reaction force is measured by the force sensor (13) during a priming of the piston (6), compared with the standard nominal value (S) and upon compliance with a predetermined, maximum permissible difference between the standard nominal value (S) and this reaction force stored in a second memory (23) of the control (20) and is used as for the apparatus specific nominal value (S′

) for the nominal/actual comparison during infusion or injection.

10. Apparatus according to claim 8, characterized in that the force sensor (13) is positioned in alignment with an axis of displacement (V) of the piston (6).

11. Apparatus according to claim 8, characterized in that a driven member (7) directly acting on the piston (6) and a drive member of the drive (7 to 11) directly coupled with the driven member (7) are floatingly and linearly displaceable supported in the housing (1).

12. The apparatus of claim 11, wherein a motor is used for the driving of the drive member.

13. Apparatus according to claim 8, characterized in that the force sensor (13) includes a bendable beam (14), the bending of which, caused by the reaction force exerted thereon, acts on a strain gauge (15) which outputs a measured value corresponding to its stretching or compression.

14. Apparatus according to claim 8, characterized in that a valve (30) is positioned in a flow cross section of the product fluid between the container (2) and an infusion or injection needle (5), said valve (30) permitting flow of the product fluid in direction of the needle (5) only upon exceeding of an over pressure defined by the valve (30).

15. A process for monitoring the pressure of a product fluid to be administered during an infusion or injection, the product fluid being dispensable from a container which is received in a housing or formed by the latter through advancement of a piston received in the container, comprising the steps of:

a) measuring a reaction force exerted by the piston on the housing and feeding the measurement to a control for a drive of the piston; and

b) comparing the measured reaction force with a predetermined reference force and controlling the drive of the piston as a result of the comparison, wherein the reference force is a nominal value for the reaction.

16. The process of claim 15, wherein the nominal value relied upon for the comparison with the measured reaction force is determined by measuring during a priming of the piston, in which the piston is displaced from an installation position in the container up to an expulsion of product fluid in a starting position for a first administration.

17. The process of claim 16, wherein the reaction force measured during priming is compared with a predetermined standard nominal value and upon compliance with a predetermined, maximum permissible difference to the standard nominal value is used as new nominal value during the administration of the fluid.

18. The process of claim 15, wherein a defined pressure drop is produced in a flow cross section of the product fluid between the container and an infusion or injection needle.

19. The process of claim 15, wherein during a priming of the piston, the piston is advanced from an installation position in the container to a starting position for a first administration, wherein a first striking of the drive against the piston is detected and the fill condition of the container is determined from the position of the drive upon contact.

20. The process of claim 15, wherein a start-stop-frequency of a step motor of the drive is adjusted such that the step motor is arrested upon a first contact of the drive on the piston, and that a fill condition of the container is determined from a position of the motor held upon striking.

21. The process of claim 15, wherein at least a first nominal value and a second nominal value for the reaction force are predetermined, wherein the first nominal value represents a reaction force to be exerted for a displacement of the piston from an at rest position and the second nominal value represents a reaction force which adopts a constant value during the displacement movement of the piston.

22. An apparatus for monitoring the pressure of a product fluid which is dispensable in dosed amounts for the purpose of an infusion or injection from a container by advancement of a piston received in the container, comprising:

a) a housing;

b) a force sensor which measures a reaction force which serves as a measure of the pressure exerted by the piston and outputs it as a measured value; and

c) a controller which compares the measured value with a predetermined reference value and controls a drive for the piston under consideration of the result of the comparison, wherein at least one nominal value for the reaction force is stored in a memory of the controller and used for a direct nominal/actual comparison with the measured reaction force.

23. The apparatus of claim 22, wherein:

a) a standard nominal value for the reaction force is stored in a first memory of the control;

b) the reaction force is measured by the force sensor during a priming of the piston;

c) the reaction force is compared with the standard nominal value; and

d) upon compliance with a predetermined, maximum permissible difference between the standard nominal value and this reaction force, the reaction force is stored in a second memory of the control and is used for the apparatus specific nominal value for the nominal/actual comparison during infusion or injection.

24. The apparatus of claim 22, wherein the force sensor is positioned in alignment with an axis of displacement of the piston.

25. The apparatus of claim 22, wherein a driven member directly acting on the piston and a drive member of the drive directly coupled with the driven member are floatingly and linearly displaceably supported in the housing.

26. The apparatus of claim 22, wherein the force sensor includes a bendable beam, the bending of which, caused by the reaction force exerted thereon, acts on a strain gauge which outputs a measured value corresponding to its stretching or compression.

27. The apparatus of claim 22, wherein a valve is positioned in a flow cross section of the product fluid between the container and an infusion or injection needle, the valve permitting flow of the product fluid in direction of the needle only upon exceeding of an over pressure defined by the valve.

28. A pressure monitoring system for an injection or infusion device, comprising:

(a) a force sensor which measures a reaction force of a piston on a drive; and

(b) a control, the control comprising a microprocessor, and at least one permanent memory, wherein the at least one permanent memory contains a predetermined standard nominal value, and the at least one permanent memory contains the measured reaction force and compares the measured reaction force to the standard nominal value.

29. The pressure monitoring system of claim 28, wherein the force sensor is a bendable beam with a strain gauge.

30. The pressure monitoring system of claim 28, wherein the at least one permanent memory contains permissible deviations from the standard nominal value.

31. The pressure monitoring system of claim 30, wherein a force measurement outside of the deviations indicate a leakage.

32. The pressure monitoring system of claim 30, wherein a force measurement outside of the standard deviation indicates an occlusion.