Bubble detector and method of use thereof

• US 6,622,542 B2
• Filed: 03/20/2001
• Issued: 09/23/2003
• Est. Priority Date: 03/20/2001
• Status: Expired due to Term

• Current Assignee: TherOx Incorporated (Asahi Kasei Corporation)
• Original Assignee: TherOx Incorporated (Asahi Kasei Corporation)
• Inventors: Patterson, William R., Creech, Jeffrey L., Derek, Daw J.
• Primary Examiner(s): Williams, Hezron
• Assistant Examiner(s): POLITZER, JAY L
• Application Number:
  US09/813,072
• Publication Number:
  US 20020134134A1
• Time in Patent Office: 917 Days
• Field of Search: 73/617.5, 73/191, 736/00, 73/190.3, 340/507, 604/65
• US Class Current: 73/19.03
• CPC Class Codes: A61M 1/32 Oxygenators without membranes
• CPC Class Codes: A61M 1/362227 the interface providing means for actuating on functional elements of the cassette, e.g. plungers
• CPC Class Codes: A61M 1/36224 with sensing means or components thereof
• CPC Class Codes: A61M 1/362262 Details of incorporated reservoirs
• CPC Class Codes: A61M 1/362265 Details of valves
• CPC Class Codes: A61M 1/3623 Means for actively controlling temperature of blood
• CPC Class Codes: A61M 1/3626 Gas bubble detectors
• CPC Class Codes: A61M 2202/0476 Oxygenated solutions
• CPC Class Codes: A61M 2209/02 Equipment for testing the apparatus
• CPC Class Codes: G01N 2291/015 Attenuation, scattering
• CPC Class Codes: G01N 2291/02433 Gases in liquids, e.g. bubbles, foams
• CPC Class Codes: G01N 2291/02466 Biological material, e.g. blood
• CPC Class Codes: G01N 35/08 using a stream of discrete samples flowing along a tube system, e.g. flow injection analysis

Abstract

A bubble detector utilizes an ultrasonic transducer to sample bubbles as they pass the transducer. The envelope of the return signal is analyzed to determine the volume of each sampled bubble. If the total volume of bubbles sampled within a certain period of time exceeds a desired maximum volume, the bubble detector may initiate a system shut down. A bubble detector can be evaluated or calibrated by introducing bubbles into a conduit, detecting the bubbles introduced into the conduit using visual inspection or a bubble detector of known resolution and comparing the results with the examination of a bubble detector under evaluation.

Claims

1. A bubble detector comprising:

an ultrasonic transducer pair comprising a transmitting transducer and a receiving transducer, the ultrasonic transducer pair being positionable to sense bubbles in a fluid flow, wherein a pressure of the fluid is higher than a patient'"'"'s blood pressure;

a transducer driver operatively coupled to the transmitting transducer to cause the transmitting transducer to deliver a pulsed ultrasonic signal across the fluid flow to the receiving transducer;

a signal conditioner operatively coupled to the receiving transducer to receive the pulsed ultrasonic signal from the receiving transducer, the signal conditioner conditioning the pulsed ultrasonic signal to produce a conditioned signal; and

a signal processor operatively coupled to the signal conditioner to receive the conditioned signal, the signal processor determining a first volume of each bubble based on the conditioned signal and converting the first volume to a second volume based on the fluid pressure and an atmospheric pressure, wherein the first volume is a measured volume of the bubble in the fluid and the second volume is a predicted volume of the bubble when it enters the patient.

2. The bubble detector, as set forth in claim 1, wherein the pulsed ultrasonic signal delivered by the transmitting transducer comprises a frequency range of 3 MHz to 4 MHz and a pulse rate of about 3 KHz to 40 KHz.

3. The bubble detector, as set forth in claim 1, wherein the signal conditioner comprises:

an amplifier adapted to amplify the pulsed ultrasonic signal from the receiving transducer.

4. The bubble detector, as set forth in claim 1, wherein the signal conditioner comprises:

a filter adapted to filter the pulsed ultrasonic signal from the receiving transducer.

5. The bubble detector, as set forth in claim 1, wherein the signal conditioner comprises:

a detector adapted to detect the amount of ultrasonic energy of the pulsed ultrasonic signal received by the receiving transducer.

6. The bubble detector, as set forth in claim 5, wherein the signal conditioner comprises:

an analog-to-digital converter adapted to convert the amount of ultrasonic energy detected by the detector into a digital signal.

7. The bubble detector, as set forth in claim 6, wherein the signal processor comprises a buffer adapted to hold multiple digital signals.

8. The bubble detector, as set forth in claim 7, wherein a reduction in the digital signal as compared to previously recorded digital signals or an average of previously recorded digital signals is correlative to bubbles in the fluid flow.

9. The bubble detector, as set forth in claim 1, wherein the signal processor comprises a digital signal processor.

10. The bubble detector, as set forth in claim 9, wherein the digital signal processor is adapted to detect and count each bubble in the fluid flow.

11. The bubble detector, as set forth in claim 1, wherein the digital signal processor determines an accumulated volume of bubbles over a given period of time.

12. The bubble detector, as set forth in claim 1, wherein the signal processor initiates a stop signal in response to the determined information.

13. The bubble detector, as set forth in claim 12, wherein the signal processor initiates the stop signal in response to the determined information indicating that the volume of bubbles when they reach a patient exceeds a predetermined limit.

14. The bubble detector, as set forth in claim 1, wherein the fluid flow is vertically downward.

15. The bubble detector, as set forth in claim 14, wherein the fluid flow is downstream of the circumferential flow region.

16. A method of detecting bubbles in a fluid flow, wherein a pressure of the fluid is higher than a patient'"'"'s blood pressure, comprising the acts of:

(a) transmitting a pulsed ultrasonic signal across the fluid flow;

(b) receiving the pulsed ultrasonic signal transmitted across the fluid flow;

(c) conditioning the received pulsed ultrasonic signal to produce a conditioned signal;

(d) processing the conditioned signal to determine a presence of bubbles in the fluid flow and a first volume of each bubble; and

(e) converting the first volume of the bubble into a second volume based on the fluid pressure and an atmospheric pressure, wherein the first volume is a measured volume of the bubble in the fluid and the second volume is a predicted volume of the bubble when it enters the patient.

17. The method, as set forth in claim 16, wherein act (a) comprises the act of:

transmitting the pulsed ultrasonic signal at a frequency range of 3 MHz to 4 MHz and at a pulse rate of about 3 KHz to 40 KHz.

18. The method, as set forth in claim 16, wherein act (c) comprises the act of:

amplifying the received pulsed ultrasonic signal.

19. The method, as set forth in claim 16, wherein act (c) comprises the act of:

filtering the received pulsed ultrasonic signal.

20. The method, as set forth in claim 16, wherein act (c) comprises the act of:

detecting an amount of ultrasonic energy received by the receiving transducer.

21. The method, as set forth in claim 16, wherein act (d) comprises:

performing an analog-to-digital conversion to convert the amount of ultrasonic energy into a digital signal.

22. The method, as set forth in claim 16, wherein act (d) comprises the act of:

storing or averaging multiple digital signals.

23. The method, as set forth in claim 22, wherein act (d) comprises the act of:

detecting a reduction in the digital signal as compared to a previously stored digital signal or an average of multiple digital signals, the reduction being correlative to bubbles in the fluid flow.

24. The method, as set forth in claim 16, wherein act (d) comprises the act of:

detecting and counting the number of bubbles in the fluid flow.

25. The method, as set forth in claim 16, wherein act (d) comprises the act of:

determining the size of each bubble in the fluid flow.

26. The method, as set forth in claim 16, wherein act (e) comprises the act of:

adding the volume of each bubble to determine an overall volume of bubbles in the fluid flow.

27. The method, as set forth in claim 16, comprising the act of:

initiating a stop signal in response to the determined information.

28. The method, as set forth in claim 16, comprising the act of:

initiating a stop signal in response to the determined information indicating that the volume of bubbles when they reach a patient exceeds a predetermined limit.

29. The method, as set forth in claim 16, wherein act (a) comprises the act of:

repetitively sampling a bubble in a fluid flow as the bubble passes through a predetermined section of a fluid passageway.

30. The method, as set forth in claim 16, wherein the fluid is vertically downward.

31. The method, as set forth in claim 30, wherein the fluid flow is downstream of a circumferential flow region.