Thermal diffusion flow probe

• US 4,354,504 A
• Filed: 09/04/1979
• Issued: 10/19/1982
• Est. Priority Date: 09/04/1979
• Status: Expired due to Term

• Current Assignee: Barrow Neurological Institute, BRO, WILLIAM J. 1/3 INTEREST, CARTER, PHILIP L., 1/3 INTEREST
• Original Assignee: William J. Bro
• Inventors: Bro, William J.
• Primary Examiner(s): Cohen, Lee S.
• Application Number:
  US06/072,148
• Time in Patent Office: 1,141 Days
• Field of Search: 128/691, 128/692, 128/713, 128/736, 73/190 H, 73/204
• US Class Current: 600/504
• CPC Class Codes: A61B 5/028 by thermo-dilution
• CPC Class Codes: G01F 1/684 Structural arrangements; Mounting of elements, e.g. in relation to fluid flow
• CPC Class Codes: G01F 1/696 Circuits therefor, e.g. constant-current flow meters

Abstract

A blood-flow probe utilizing two-terminal integrated circuit temperature transducers each of which produces an output current proportional to the absolute temperature of the probe contact plate with which the temperature transducer is associated. One such temperature transducer monitors the temperature of the cold plate of the probe. The other temperature transducer monitors that of the hot plate. Each transducer output signal is carried from the probe so that the temperature of the hot plate and of the cold plate may be independently measured. The hot plate temperature is monitored and maintained at a safe level so as not to endanger the patient by causing tissue damage.

Claims

1. In a thermodiffusion blood-flow probe system comprising a thermodiffusion probe having a hot and a cold body-tissue-contact plate wherein the temperature gradient between said plates is independent of ambient body-tissue temperature but varies with blood flow through said body tissues the improvement comprising:

(a) first signal means coupled to said hot contact plate for outputting a signal proportional to the temperature of said hot plate;

(b) second signal means coupled to said cold contact plate for outputting a signal proportional to the temperature of said cold plate;

(c) reference signal means for outputting a signal proportional to a selected safe temperature to which body tissue may be exposed without damage while said probe is used to determine blood flow; and

(d) comparison means for comparing the relative level of the output of said reference signal means and the output of said first signal means.

2. The system of claim 1 wherein said first signal means is a semiconductor device.

3. The system of claim 1 wherein said second signal means is a semiconductor device.

4. The system of claim 2 wherein said semiconductor device is an integrated circuit temperature transducer.

5. The system of claim 3 wherein said semiconductor device is an integrated circuit temperature transducer.

6. The system of claim 1 further comprising means for determining a change in the relative levels of said signal proportional to said hot plate and said signal proportional to said cold plate.

7. The system of claim 6 wherein said change determining means comprises:

(a) a first input port coupled to the output of said first signal means;

(b) a second input port coupled to the output of said second signal means; and

(c) an output port for outputting a signal proportional to any change in the relative levels of signals output by said first and second signal means.

8. The system of claim 7 wherein said change determining means is a differential amplifier.

9. The system of claim 7 further comprising means for monitoring the signal output from change determining means.

10. The system of claim 1 wherein said comparison means comprises a comparator having:

(a) a first input port coupled to said reference signal means;

(b) a second input port coupled to said first signal means; and

(c) an output port for outputting a signal determinative of the fact that the signal input to said second input port of said comparator has exceeded the limit established by the reference signal input to said first input port of said comparator.

11. The system of claim 10 further comprising a monitoring port coupled to the output port of said comparator.

12. The system of claim 10 having reaction means to effect a change in temperature of the said hot contact plate in response to said signal output by said comparator.

13. The system of claim 12 having a thermoelectric heat pump coupled to said hot and said cold contact plates.

14. The system of claim 13 having power supply means coupled to said heat pump for providing the necessary drive to power said heat pump.

15. The system of claim 14 having means for controlling the coupling of said power supply means to said heat pump being responsive to said reaction means so as to control the application of said drive to said heat pump.

16. The system of claim 12 having ground coupling means for maintaining said hot and said cold contact plates at primary power line ground potential.

17. The system of claim 10 having a thermoelectric heat pump coupled to said hot and said cold contact plates.

18. The system of claim 10 having ground coupling means for maintaining said hot and said cold contact plates at primary power line ground potential.

19. The system of claim 1 having a thermoelectric heat pump coupled to said hot and said cold contact plates.

20. The system of claim 1 having ground coupling means for maintaining said hot and said cold contact plates at primary power line ground potential.

21. The system of claim 1 wherein said probe has body means fabricated of materials known to be compatible with body tissue so as to cause no tissue damage while in use.

22. The system of claim 1 further comprises signal transmission means for conveying signals from said probe to various associated monitoring ports and devices.

23. The system of claim 22 wherein said transmission means comprises electrical conductors.

24. The system of claim 23 wherein said electrical conductors are sheathed in materials known to be compatible with body tissue so as to cause no tissue damage while said probe is in use.

25. In a thermodiffusion blood flow probe system comprising a thermodiffusion probe having a hot and cold body-tissue-contact plate wherein the temperature gradient between said plates is independent of ambient body-tissue temperature but varies with blood flow through said body tissue, the improvement comprising:

(a) first signal means coupled to said hot contact plate for outputting a signal proportional to the temperature of said hot plate;

(b) second signal means coupled to said cold contact plate for outputting a signal proportional to the temperature of said cold plate; and

(c) monitoring means coupled to at least one of said first and second signal means for monitoring at least one of said signal output by said first and second signal means.