DETERMINING FLOW RATE

• US 20120001762A1
• Filed: 06/20/2008
• Published: 01/05/2012
• Est. Priority Date: 08/06/2007
• Status: Abandoned Application

• Current Assignee: Smith & Nephew PLC
• Original Assignee: Smith & Nephew PLC
• Inventors: Turner, Jake, Gordon, Benjamin
• Application Number:
  US12/672,063
• Publication Number:
  US 20120001762A1
• Time in Patent Office: Days
• US Class Current: 340/626
• CPC Class Codes: A61M 1/73 comprising sensors or indicators for physical values
• CPC Class Codes: A61M 1/74 Suction control underwater drainage A61M1/61
• CPC Class Codes: A61M 1/784 by filtering, sterilising or disinfecting the exhaust air, e.g. swellable filter valves
• CPC Class Codes: A61M 1/96 Suction control thereof
• CPC Class Codes: A61M 1/966 having a pressure sensor on or near the dressing
• CPC Class Codes: A61M 1/984 portable on the body
• CPC Class Codes: A61M 2205/3331 Pressure; Flow
• CPC Class Codes: A61M 2205/3365 Rotational speed

Abstract

A method and apparatus are disclosed for determining a flow rate in a topical negative pressure (TNP) system. The method includes the steps of determining a pumping speed associated with a pump element of a TNP system, determining a pressure associated with a flow path associated with the pump element, and determining flow rate in the flow path responsive to the pumping speed and flow rate.

Claims

1. A method of determining flow rate in a topical negative pressure (TNP) system, comprising the steps of:

determining a pumping speed associated with a pump element of a TNP system;

determining a pressure associated with a flow path associated with the pump element; and

determining indirectly flow rate in the flow path using a relationship between the pumping speed and the pressure.

2. The method as claimed in claim 1, further comprising the steps of:

determining the pressure by measuring pressure via a pressure sensor.

3. The method as claimed in claim 1 wherein the flow rate comprises a load on the pump element.

4. The method as claimed in claim 1 wherein the step of determining the pumping speed comprises the steps of:

determining an electromotive force (EMF) generated by a free-wheeling element of the pump element; and

calculating the pumping speed responsive to the generated EMF.

5. The method as claimed in claim 1, further comprising the steps of:

determining if the determined flow rate is within a predetermined operating range; and

generating at least one of an audible and/or visible alarm cue if the determined flow rate exceeds an upper range limit or falls below a lower range limit.

6. The method as claimed in claim 1, further comprising the steps of:

periodically varying pump speed responsive to the determined flow rate;

re-determining the pressure subsequent to each step of varying pump speed; and

re-determining flow rate in the flow path.

7. The method as claimed in claim 1 wherein the step of determining flow rate comprises the steps of:

determining flow rate at an inlet location of the pump element.

8. The method as claimed in claim 1, further comprising determining flow rate in the flow path by the steps of:

determining a pump speed or pressure;

indexing a look-up table responsive to the determined pump speed or pressure; and

determining a flow rate by indexing a flow rate value associated with a value of a remainder of the pump speed or pressure in the indexed look-up table.

15. The method as claimed in claim 1, wherein determining flow rate in the flow path comprises:

selecting a look-up table based on the determined pump speed; and

determining the flow rate by selecting a flow rate value associated with the determined pressure in the selected look-up table.

16. The method as claimed in claim 1, wherein determining flow rate in the flow path comprises:

selecting a look-up table based on the determined pressure; and

determining the flow rate by selecting a flow rate value associated with the determined pump speed in the selected look-up table.

17. The method as claimed in claim 1, further comprising:

determining a second value for the flow rate using a flow rate sensor;

comparing the determined flow rate with the second value for the flow rate; and

in response to the comparison, generating an alarm signal if a discrepancy between the determined flow rate and the second value for the flow rate is found.

9. Apparatus for determining flow rate in a topical negative pressure (TNP) system, comprising:

a pump element, comprising a rotor element configured to provides negative pressure in a flow path;

a pressure sensor arranged to determine a pressure in the flow path; and

a processing unit configured to;

determines a pumping speed associated with the pump element; and

determines indirectly flow rate in the flow path using a relationship between to the pumping speed and the pressure.

18. The apparatus as claimed in claim 9 wherein the processing unit is configured to determine flow rate in the flow path by the steps comprising:

select a look-up table based on the determined pump speed; and

determine the flow rate by selecting a flow rate value associated with the determined pressure in the selected look-up table.

19. The apparatus as claimed in claim 9 wherein the processing unit is configured to determine flow rate in the flow path by the steps comprising:

select a look-up table based on the determined pressure; and

determine the flow rate by selecting a flow rate value associated with the determined pump speed in the selected look-up table.

10. The apparatus as claimed in claim 10 wherein the flow path comprises:

a connection tube connecting the pump element to a canister of the TNP system; and

an aspirant tube connected to the canister and locatable at a wound site.

11. The apparatus as claimed in claim 10, further comprising:

a pulse width modulation (PWM) generator that provides an output signal which provides a drive voltage for the pump element and which receives a control signal that selectively disconnects the pump element from the drive voltage.

12. The apparatus as claimed in claim 10, further comprising:

the processing unit calculates an electro motive force (EMF) generated by a free-wheeling rotor element and calculates pumping speed responsive to the EMF.

13. (canceled)

14. (canceled)