Apparatus and Method for Estimating Leakage in a Surgical Tourniquet System

• US 20100204726A1
• Filed: 02/10/2009
• Published: 08/12/2010
• Est. Priority Date: 02/10/2009
• Status: Active Grant

• Current Assignee: Western Clinical Engineering Ltd.
• Original Assignee: Western Clinical Engineering Ltd.
• Inventors: Gebert, Michael A., Cheung, William K.W., McEwen, James A., Jameson, Michael
• Granted Patent: US 8,083,763 B2
• Time in Patent Office: Days
• US Class Current: 606/202
• CPC Class Codes: A61B 17/1355 Automated control means therefor
• CPC Class Codes: A61B 2017/00119 alarm; indicating an abnormal situation
• CPC Class Codes: A61B 2017/00132 Setting operation time of a device A61B2017/00123 takes precedence
• CPC Class Codes: A61B 2017/00199 with a console, e.g. a control panel with a display
• CPC Class Codes: A61B 2090/064 for measuring force, pressure or mechanical tension
• CPC Class Codes: A61B 2090/0809 Indication of cracks or breakages

Abstract

Apparatus for estimating a magnitude of leakage from a surgical tourniquet system while pressure in a cuff of the system is regulated near a reference pressure.

Claims

1. Apparatus for estimating the magnitude of leakage of pressurized gas from a surgical tourniquet system, comprising:

an inflatable tourniquet cuff having pneumatic tubing for connecting the cuff to a pressure regulator assembly, thereby establishing a gas passageway between the cuff and the pressure regulator assembly;

wherein the pressure regulator assembly is operable to direct pressurized gas to and from the cuff and passageway to maintain pressure in the cuff within a reference pressure level range during a time period; and

a leak detector for estimating a magnitude of leakage of pressurized gas from the cuff or passageway by monitoring a level of a parameter of operation of the pressure regulator assembly that is indicative of a rate of flow of pressurized gas to the cuff and passageway during the time period.

2. The apparatus as defined in claim 1 wherein the pressure regulator assembly is configured to supply pressurized gas to the cuff and passageway when actuated by an electrical signal, wherein the leak detector monitors the level of the electrical signal throughout the time period, and wherein the estimate of the magnitude of leakage is a predetermined function of the level of the electrical signal throughout the time period.

3. The apparatus as defined in claim 1 wherein the level of the parameter corresponds to an amount by which the reference pressure level exceeds the level of pressure maintained by the pressure regulator assembly in the cuff and passageway throughout the time period.

4. The apparatus as defined in claim 1 wherein the magnitude of leakage is estimated by the leak detector to be a predetermined function of the level of the parameter of operation of the pressure regulator assembly that is indicative of a rate of flow of pressurized gas to the cuff and passageway throughout the time period.

5. The apparatus as defined in claim 1 wherein the leak detector further monitors a level of a second parameter of operation of the pressure regulator assembly that is indicative of the rate of flow of pressurized gas to the cuff and passageway during the time period, and wherein the leak detector further estimates the magnitude of leakage using the second parameter level.

6. The apparatus as defined in claim 1 wherein the leak detector further monitors a level of a second parameter of operation of the pressure regulator assembly that is indicative of the rate of flow of pressurized gas from the cuff and passageway during the time period, and wherein the leak detector further estimates the magnitude of leakage using the second parameter level.

7. The apparatus as defined in claim 1 wherein the time period during which the leak detector estimates the magnitude of leakage is substantially greater than the time required by the pressure regulator assembly to restore the level of pressure in the cuff within the predetermined range in response to a transient event that is not attributable to leakage.

8. The apparatus as defined in claim 1 wherein the leak detector further stores a value indicative of the estimate of the magnitude of leakage, and wherein the apparatus further includes communication means for communicating the stored value to a location remote from the apparatus and for presentation of the stored value in a form perceptible by a user.

9. The apparatus as defined in claim 1 wherein the leak detector ranks the estimate of the magnitude of leakage and includes means for producing a leakage warning indication perceptible by a user if the estimate of the magnitude of leakage is greater than a predetermined hazardous level of leakage.

10. The apparatus as defined in claim 1 wherein the leak detector estimates the magnitude of leakage during two separate time periods and further includes trend means for producing a leakage trend value indicative of the amount of difference between the two estimates.

11. The apparatus as defined in claim 10 and including means for producing a leakage trend indication perceptible by a user if the leakage trend value is greater than a predetermined hazardous trend threshold level.

12. Apparatus for estimating the magnitude of leakage from a surgical tourniquet system, comprising:

an inflatable tourniquet cuff having pneumatic tubing and a releasable connector for connecting the cuff to a pressure regulator, thereby establishing a gas passageway between the cuff and the pressure regulator;

pressure regulator operable by selectively actuating pressure increase means and pressure decrease means to maintain the pressure in the cuff and passageway near a reference pressure level during a time period, and wherein the pressure regulator is further operable for producing a regulator alarm if the difference between the reference pressure level and the pressure in the cuff and passageway exceeds a predetermined difference limit at a time during the time period; and

leak detector for producing an estimate of a magnitude of leakage of pressurized gas from the cuff and passageway, wherein the estimate of the magnitude of leakage is indicative of a flow of pressurized gas into the cuff and passageway from the pressure regulator during the time period.

13. The apparatus as defined in claim 12 wherein the leak detector further inhibits the production of an estimate of the magnitude of leakage if the regulator alarm is produced.

14. The apparatus as defined in claim 12 and including a user interface for presenting an indication of the estimate of the magnitude of leakage in a form perceptible by a user.

15. The apparatus as defined in claim 12 and including communication means for communicating an indication of the estimate of the magnitude of leakage to remote apparatus.

16. A method of estimating the magnitude of fluid leakage from a surgical tourniquet cuff during an operation time period that the cuff is applied to a patient'"'"'s limb and connected to a controllable pressure source of fluid and pressurized with the fluid to be within a reference pressure range suitable for occluding blood flow through the limb, the method comprising the steps of:

estimating the rate of flow of fluid into the cuff during the operation time period;

differentiating between flow of fluid into the cuff that is and is not attributable to leakage; and

based on the foregoing steps, estimating the magnitude of the fluid leakage.

17. The method of claim 16 wherein the estimating step includes the step of monitoring an electrical signal that controls the controllable pressure source.

18. The method of claim 16 including the step of accounting for a flow of fluid intentionally vented from the cuff.

19. The method of claim 16 including the step of determining the trend in the magnitude of leakage by comparing two estimates of the magnitude of leakage.

20. The method of claim 16 including the steps of ranking the estimated magnitude of leakage and providing to a user an indication corresponding to that ranking.

21. The method of claim 16 wherein the differentiating step includes monitoring the flow of fluid into the cuff for a monitoring period that is greater than about two seconds.

22. A method of estimating the magnitude of leakage from a tourniquet cuff of a surgical tourniquet system while pressure in the cuff is regulated near a reference pressure, comprising the steps of:

applying an inflatable tourniquet cuff to a patient'"'"'s limb;

connecting the tourniquet cuff to a tourniquet pressure regulator and employing the pressure regulator to inflate the cuff,

regulating a pressure in the cuff near a reference pressure level during a time period by selectively providing an inflow of pressurized gas from the pressure regulator to increase the pressure in the cuff and by selectively allowing an outflow of pressurized gas through the pressure regulator to decrease the pressure in the cuff; and

estimating a magnitude of leakage of pressurized gas from the cuff by monitoring a level of a parameter of operation of the pressure regulator indicative of flow of pressurized gas into the cuff and passageway during the time period.