WO2008097572A2

WO2008097572A2 - Device for blood temperature measurement in-vivo

Info

Publication number: WO2008097572A2
Application number: PCT/US2008/001565
Authority: WO
Inventors: Kenneth R. Kensey; Daniel J. Cho
Original assignee: Kensey Kenneth R; Cho Daniel J
Priority date: 2007-02-06
Filing date: 2008-02-06
Publication date: 2008-08-14
Also published as: WO2008097572A3

Abstract

A device for the measurement of the temperature of blood in-vivo which includes a penetrator configured for the penetration of a blood vessel and a temperature sensor residing on the penetrator.

Description

DEVICE FOR BLOOD TEMPERATURE MEASUREMENT IN-VIVO

RELATED APPLICATION

[0001] This application is based on and claims priority to U.S. Provisional

Application No. 60/888,406, filed February 6, 2007, entitled Disposable Needle for Core- Body Temperature Measurement to which a claim of priority is hereby made and the disclosure of which is incorporated by reference.

FIELD OF THE INVENTION

[0002] The present invention relates generally to blood temperature measurements, and more specifically to a device for in- vivo measurement of the temperature of the blood and a method for measuring a hemorheological property.

BACKGROUND AND SUMMARY OF THE INVENTION

[0003] Hemorheology is a field of study related to understanding and measuring physico-chemical properties of blood moving in the arterial and the venous systems. Hemorheological properties include whole blood viscosity, plasma viscosity, hematocrit, red blood cell (erythrocytes) aggregation and deformability, thrombotic tendency, erythrocyte sedimentation rate, partial pressures of oxygen and carbon dioxide in blood, glucose, ALT, and C-reactive protein. Hemorheological properties may vary depending on the blood temperature which has a direct bearing on the flow parameters including the viscosity of the blood in the circulatory system.

[0004] It is well known that liquid viscosity depends on the solution temperature and the relationship between the viscosity and temperature is often described by the following Andrade equation:

μ(T) = Ae BIT where A and B are constants for a liquid. As is apparent from the Andrade equation, blood viscosity would decrease with increasing temperature. As a rule of thumb, whole blood viscosity increases about 5% per degree reduction in temperature (Celsius). Alternatively, it can be said that whole blood viscosity decreases about 5% per degree increase in temperature. Hence, the whole blood viscosity in a person can significantly vary depending on the person's core-body temperature. For example, in the case of a smoker, when nicotine is introduced into the body, blood vessels undergo vasoconstriction due to the excitation in the sympathetic nerve system. As the diameter of peripheral blood vessels is reduced due to vasoconstriction, the amount of blood flow through the peripheral vessels will decrease, making the hands and feet cold. The cold hands and feet will increase the blood viscosity locally, thus further increasing the flow resistance in the peripheral blood vessels. This, in turn, further reduces the blood flow at the hands and feet, making them colder and initiating a vicious cycle of impaired blood flow at the peripheral vessels.

It is well known that whole blood viscosity can be measured using a scanning capillary tube viscometer (SCTV) at a predetermined temperature in-vitro. Specifically, the method involving the use of SCTV requires the removal of a small amount of whole blood (approximately 2-5 cc) from a body and the introduction of the same to the SCTV, which is maintained at a fixed temperature of, for example, 37⁰C. Because the SCTV method is carried out at a pre-determined and arbitrary temperature it does not take into account the temperature effect on the blood viscosity measurement. That is, it does not measure the whole blood viscosity of a person at the person's core-body temperature and thus does not accurately determine whole blood viscosity of blood in the circulatory system of the person.

SUMMARY OF THE INVENTION

[0005] Since blood is continuously circulated around the body through the heart approximately once a minute, the temperature of the circulating blood is relatively unchanged throughout the body.

[0006] A device according to the present invention allows for the measurement of the temperature of the blood in-vivo which can be then used to accurately determine the whole blood viscosity or another hemorheological parameter. [0007] Specifically, a device according to the present invention includes a penetrator configured to penetrate a blood vessel, and a temperature sensor residing on a surface of the penetrator. In the preferred embodiment, the penetrator can be a needle, such as a hollow-body needle having a channel in which the temperature sensor resides on an interior surface of the channel. Preferably, the temperature sensor can include a thermocouple. A signal processor can be coupled to the thermocouple to determine the temperature of the blood in- vivo and in real time.

[0008] In a method according to the present invention includes inserting a temperature sensor into a blood vessel of a human, and measuring the temperature of blood in the blood vessel in-vivo using the temperature sensor. The temperature so measured can be then used to determine a hemorheological parameter. For example, in one preferred embodiment, a temperature so measured can be used to determine the whole blood viscosity using SCTV by setting the temperature to the measured temperature during the SCTV test rather than an arbitrary temperature.

[0009] Other features and advantages of the present invention will become apparent from the following description of the present invention and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Fig. 1 schematically illustrates a device according to a preferred embodiment of the present invention.

[0011] Fig. 2 schematically illustrates a device according to the preferred embodiment being used to carry out a method according to the preferred embodiment of the present invention.

DETAILED DESCRIPTION

[0012] Referring to Fig. 1, a device according to the present invention includes a penetrator 10 configured to penetrate a blood vessel. Thus, for example, penetrator 10 may be a needle having a sharp tip 12 capable of piercing a blood vessel and a narrow body that would allow for the insertion of at least a portion thereof inside a blood vessel. A device according to the present invention further includes a temperature sensor 14 which resides on a surface of penetrator 10 that is designated for entry into a blood vessel, whereby temperature sensor 14 may be placed in contact with blood in a blood vessel in-vivo. [0013] In the preferred embodiment, penetrator 10 may be a hollow-body needle having a through-channel 16 therein in which temperature sensor 14 resides on a surface of an interior wall 18 of channel 16 and flush-mounted near the tip of the needle. Preferably, channel 16 terminates at two opposing open ends. First open end 20 is designated for communication with blood in the blood vessel once penetrator 10 penetrates the blood vessel, and second open end 22 is designated for coupling to the inlet port of a blood sample collection chamber or the like of, for example, a syringe. Note that sensor 14 may include input/output terminals which are preferably coupled to an outside processor via, for example, wires 24 or the like. The electrical signals produced by sensor 14 are transmitted via at least one of the wires 24 for analysis outside the patient's body. [0014] Alternatively, penetrator 10 may be a solid-body needle, and sensor 14 resides on an exterior surface of the needle flush-mounted at the tip thereof. [0015] Referring now to Fig. 2, in which like numerals identify like features, in a method according to the present invention penetrator 10, which is preferably a hollow-body needle, is inserted into a blood vessel 26 (for example, the needle is inserted into a vein accessed from the forearm such as the anti-cubital vein, which is often the site for removing blood samples for blood tests), thereby inserting temperature sensor 14, which may be preferably a thermocouple, into blood stream 28. Thereafter, the temperature of blood 28 in vessel 26 is measured in-vivo in real time. Specifically, electrical signals from temperature sensor 14 are transmitted to a signal processor 31, which then processes the signals to determine the temperature of blood 28 in vessel 26. Signal processor 31 preferably converts the μV signal produced by the thermocouple to a mV signal first and then converts the electrical signal into temperature measurements. Signal processor 31 may be a conventional personal computer (PC) programmed to calculate the temperature of blood 28 from the signals received from sensor 14 or the like device.

[0016] Note that, in one preferred embodiment, second open end of penetrator 10 may be in communication with open inlet port 30 of a blood sample collection chamber 32 of a syringe or the like. In a preferred method, blood 28 may be drawn into channel 16 by the operation of the plunger (not shown) residing inside chamber 32 whereby blood may be forced to flow over temperature sensor 14.

[0017] The temperature so measured can be then used to determine a hemorheological parameter such as whole blood viscosity. For example, the temperature so measured can be used for the determination of whole blood viscosity in an in- vitro test such as SCTV, which uses a predetermined temperature.

[0018] For example, a person who is a non-smoker may have a blood temperature of 38⁰C and another person who is a smoker may have a blood temperature of 36⁰C. In both cases, using a conventional SCTV test, the whole blood viscosity is determined at a predetermined temperature of 37⁰C. If it is assumed that the measured viscosities from the two people are exactly identical, and the effect of the blood temperature on the blood viscosity is not taken into account, it may be concluded erroneously that the whole blood viscosity for a non-smoker and a smoker are the same, implying that smoking does not adversely affect blood viscosity. However, when the effect of the blood temperature, as determined by a method according to the present invention, is taken into account, the non- smoker's whole blood viscosity can be corrected to be 5% greater than the measured value, whereas the non-smoker's whole blood viscosity can be corrected to be 5% smaller than the measured value. Hence, it can be concluded that the smoker's viscosity is about 10% greater than that of the non-smoker, resulting in a significant clinical implication. Thus, in one embodiment of the present invention, the temperature of the blood measured according to the present invention can be used to correct the whole blood viscosity or another hemorheological parameter in the circulatory system measured by a conventional method at a pre-determined temperature. Other hemorheological parameters which can be corrected/reinterpreted include plasma viscosity, serum viscosity, and yield stress of blood. [0019] Although the present invention has been described in relation to particular embodiments thereof, many other variations and modification and other uses will become apparent to those skilled in the art. It is preferred, therefore, that the present invention be limited not by the specific disclosure herein, but only by the appended claims.

Claims

WHAT IS CLAIMED IS:

1. A device for the measurement of the temperature of blood in- vivo, comprising: a penetrator configured to penetrate a blood vessel; and a temperature sensor residing on a surface of said penetrator.

2. The device of claim 1, wherein said penetrator is a needle.

3. The device of claim 1, wherein said penetrator comprises a hollow-body needle having a channel, and wherein said temperature sensor resides on an interior surface of said channel.

4. The device of claim 3, wherein said temperature sensor comprises a thermocouple.

5. The device of claim 1, wherein said temperature sensor comprises a thermocouple.

6. The device of claim 1, wherein said penetrator comprises a hollow-body needle having a channel coupled to a chamber, and wherein said temperature sensor resides on an interior surface of said channel.

7. The device of claim 6, wherein said temperature sensor is a thermocouple.

8. The device of claim 1, further comprising a signal processor coupled to said temperature sensor.

9. The device of claim 1, wherein said penetrator comprises a solid-body needle and wherein said temperature sensor resides on the exterior surface at the tip of said needle.

10. A method of measuring the temperature of blood in- vivo comprising: inserting a temperature sensor into a blood vessel of a human; and measuring a temperature of blood in said blood vessel in- vivo using said temperature sensor.

11. The method of claim 10, wherein said temperature sensor is inserted into said blood vessel using a penetrator.

12. The method of claim 11, wherein said penetrator is a needle.

13. The method of claim 12, wherein said needle includes an internal channel and wherein said temperature sensor resides on an interior wall of said internal channel.

14. The method of claim 13, further comprising a chamber coupled to said internal channel of said needle.

15. The method of claim 14, wherein said temperature sensor comprises a thermocouple.

16. The method of claim 10, wherein said temperature sensor comprises a thermocouple.

17. A method of measuring the temperature of blood in- vivo comprising: inserting a temperature sensor into a blood vessel of a human; measuring a temperature of blood in said blood vessel in- vivo using said temperature sensor; and using said temperature in conjunction with a hemorheological test to determine a hemorheological parameter of said blood.

18. The method of claim 17, wherein said hemorheological parameter is whole blood viscosity.

19. The method of claim 17, wherein said hemorheological parameters are plasma and serum viscosities.

20. The method of claim 17, wherein said hemorheological parameter is yield stress.

21. The method of claim 17, wherein said hemorheological test is SCTV.

22. The method of claim 18, wherein said temperature is used to correct a result of a SCTV test.