Pressure measurement device comprising a motorized load sensor and a process for controlling the device

• US 20020073782A1
• Filed: 12/07/2001
• Published: 06/20/2002
• Est. Priority Date: 12/08/2000
• Status: Active Grant

• Current Assignee: Industries Gambro
• Original Assignee: Industries Gambro
• Inventors: Court, Thierry, Chevallet, Jacques
• Granted Patent: US 6,976,964 B2
• Time in Patent Office: Days
• US Class Current: 73/700
• CPC Class Codes: A61M 1/3622 with a cassette forming partially or totally the blood circuit
• CPC Class Codes: A61M 1/36224 with sensing means or components thereof
• CPC Class Codes: A61M 1/36225 with blood pumping means or components thereof
• CPC Class Codes: A61M 1/36226 Constructional details of cassettes, e.g. specific details on material or shape
• CPC Class Codes: A61M 1/3639 Blood pressure control, pressure transducers specially adapted therefor
• CPC Class Codes: A61M 1/3641 Pressure isolators
• CPC Class Codes: A61M 2205/12 with interchangeable cassettes forming partially or totally the fluid circuit
• CPC Class Codes: G01L 19/0023 for flowthrough systems having a flexible pressure transmitting element
• CPC Class Codes: G01L 19/02 Arrangements for preventing, or for compensating for, effects of inclination or acceleration of the measuring device; Zero-setting means for aneroid barometers G01L7/14

Abstract

The invention proposes a device for measuring the pressure of blood, intended to engage with a section (16) for measuring the pressure of blood, which section comprises a membrane (38) which is axially deformable under the effect of the blood pressure and which is designed to be mounted on a support structure (20, 22) bearing especially a load sensor (26) arranged substantially facing the membrane (38), characterized in that it comprises controlled means (58) for the relative axial displacement of the sensitive member (52) of the load sensor (26), with respect to the support structure (20, 22), so that the axial position of the sensitive member (52) can be adjusted with respect to the external face (42) of the membrane (38), especially for the purpose of carrying out an initial calibration operation.

The invention also proposes a process for controlling the device.

Claims

1. Device for measuring the pressure of blood, intended to engage with a section (16) for measuring the pressure of blood flowing in a pipe (14), the pressure measurement section (16) comprising, in a substantially rigid wall (34), a hole (36) which is sealed by a closure element (38), the internal face (40) of which is in contact with the blood and the external face (42) of which is in contact with the ambient air, it being possible to elastically deform or displace the closure element (38) overall along a deformation or displacement axis (A-A), which is substantially orthogonal to its general plane, under the effect of the blood pressure, the pressure measurement device comprising a load sensor (26) secured to a support structure (20, 22) designed to support the pressure measurement section (16) in such a way that the load sensor (26) is placed substantially facing the closure element (38), along the deformation axis (A-A), the load sensor (26) being designed to be in contact, via the axial end of a sensitive member (52), with the external face (42) of the closure element (38) so as to measure the force applied axially to the internal face (40) of the closure element (38) by the blood pressure, in order to calculate therefrom the value of this pressure, characterized in that:

in order to operate a measurement, the load sensor (26) co-operates with the external face (42) of the associated closure element (38) only by contact;

the device (10) comprises means (58) for the relative axial displacement of the sensitive member (52), or of the measurement section (16), with respect to the support structure (20, 22), towards the closure element (38);

the device (10) comprises a control system of the means (58) for the axial displacement of the sensitive member (52), or of the measurement section (16), such that, during an initial adjustment phase of the axial position of the sensitive member (52) with respect to the external face (42) of the associated closure element (38), the sensitive member (52) comes to contact with the external face (42) of the closure element (38) and applies a given initial pretensioning force (F₀), in order to make the pressure measurement device (10) suitable for measurement of blood pressure greater than the ambient air pressure and for measurement of blood pressure less than the ambient air pressure.

2. Device (10) according to the preceding claim, characterized in that the axial displacement means (58) comprise a device (74) for immobilizing the sensitive member (52), of the respective measurement section (16), in a chosen axial position.

3. Device (10) according to any one of the preceding claims, characterized in that the axial displacement means (58) comprise a linear actuator (58) which is capable of axially displacing the load sensor (26) and its sensitive member (52).

4. Device (10) according to either of claims 1 and 2, characterized in that it comprises a load transmitter (52) which is inserted between the closure element (38) and the load sensor (26) which is fixed, and in that the displacement of the load transmitter (52), which is axial with respect to the load sensor (26), is controlled by a linear actuator (58).

5. Device (10) according to either of claims 3 and 4, characterized in that the linear actuator (58) comprises an electric motor (62) of the stepper-motor type.

6. Device (10) according to any one of the preceding claims, characterized in that the closure element (38) is made in a single part with the associated rigid wall (34).

7. Device (10) according to the preceding claim, characterized in that the closure element (38) is moulded with the associated rigid wall (34).

8. Device (10) according to any one of the preceding claims, characterized in that it comprises a control system which controls the axial displacement means (58) so that an initial calibration operation, which consists in choosing the axial position of the sensitive member (52), respectively of the measurement section (16), with respect to the external face (42) of the closure element (38), respectively with respect to the axial end of the sensitive member (52), is carried out when the closure element (38) is in its rest state, this rest state corresponding to the absence of a pressure gradient between its external face (42) and its internal face (40).

9. Device (10) according to the preceding claim, characterized in that the control system controls the axial displacement means (58) so that, during the initial calibration operation, the axial displacement of the sensitive member (52) towards the external face (42) of the closure element (38), respectively the axial displacement of the measurement section (16) towards the axial end of the sensitive member (52), is provoked until to obtain an initial pretensioning force (F₀) which is high enough so that the pressure measurement device (10) works in a linear region of the axial displacement means (58) where axial play has no effect on the pressure measurements.

10. Device (10) according to any one of the preceding claims, characterized in that it comprises a control system which controls the axial displacement means (58) so that the response of the closure element (38) to a pretensioning force (F₀) can be analysed as a function of an axial displacement of the sensitive member (52), respectively of the measurement section (16).

11. Device (10) according to the preceding claim, characterized in that the analysis of the response of the closure element (38) is aimed to determine an optimum pretensioning force (F₀) for measurements of blood pressure greater than the ambient air pressure and for measurements of blood pressure less than the ambient air pressure.

17. Process according to claim 15 or 16, characterized in that the analysis phase is used for the purpose of determining an optimum pretensioning force (F₀) for measurements of blood pressure greater than the ambient air pressure and for measurements of blood pressure less than the ambient air pressure.

12. Process for controlling a device (10) for measuring the pressure of blood, intended to engage with a section (16) for measuring the pressure of blood flowing in a pipe (14), the pressure measurement section (16) comprising, in a substantially rigid wall (34), a hole (36) which is sealed by a closure element (38), the internal face (40) of which is in contact with the blood and the external face (42) of which is in contact with the ambient air, it being possible to elastically deform or displace the closure element (38) overall along a deformation or displacement axis (A-A), which is substantially orthogonal to its general plane, under the effect of the blood pressure, the pressure measurement device comprising a load sensor (26) secured to a support structure (20, 22) designed to support the pressure measurement section (16) in such a way that the load sensor (26) is placed substantially facing the closure element (38), along the deformation axis (A-A), the load sensor (26) being designed to be in contact, via the axial end of a sensitive member (52), with the external face (42) of the closure element (38) so as to measure the force applied axially to the internal face (40) of the closure element (38) by the blood pressure, in order to calculate therefrom the value of this pressure,

characterized in that, during an initial adjustment phase of the axial position of the sensitive member (52) with respect to the external phase (42) of the associated closure element (38), the sensitive member (52), or the measurement section (16), is axially moved, with respect to the support structure (20, 22), towards the closure element (38), respectively towards the axial end of the sensitive member (52), such that the sensitive member (52) comes to contact with the external face (42) of the closure element (38) and applies a given initial pretensioning force (F₀), in order to make the pressure measurement device (10) suitable to measurement of blood pressure greater than the ambient air pressure and to measurement of blood pressure less than the ambient air pressure.

13. Process according to the preceding claim, characterized in that the initial adjustment phase comprises an initial calibration operation, and that, during the initial calibration operation, the sensitive member (52), respectively the measurement section (16), is axially moved towards the external face (42) of the associated closure element (38), respectively towards the axial end of the associated sensitive member (52), up to a given axial position of reference in which the sensitive member (52) is in contact with the external face (42) of the closure element (38), with a view to establish a correlation between a given pretensioning force (F₀) and the rest state of the closure element (38), this rest state corresponding to an absence of a pressure gradient between its external face (42) and its internal face (40).

14. Process according to the preceding claim, characterized in that, during the initial calibration operation, the sensitive member (52), respectively the measurement section (16), is axially moved towards the external face (42) of the closure element (38), respectively towards the axial end of the sensitive member (52), until the sensitive member (52) applies an initial pretensioning force (F₀) which is high enough so that the pressure measurement device (10) works in a linear region of the axial displacement means (58) where axial play has no effect on the pressure measurements.

15. Process according to any one of claims 12 to 14, characterized in that the initial adjustment phase comprises an analysis phase, and that the analysis phase consists in analysing the response of the closure element (38) to a pretensioning force (F₀) varying as a function of an axial displacement of the sensitive member (52), respectively of the measurement section (16).

16. Process according to the preceding claim, characterized in that the analysis phase is used for the purpose of identifying a fault in the structure of the closure element (38).