System and method for non-invasively monitoring hemodynamic parameters

• US 6,280,390 B1
• Filed: 12/29/1999
• Issued: 08/28/2001
• Est. Priority Date: 12/29/1999
• Status: Expired due to Fees

• Current Assignee: Ramot University Authority For Applied Research and Industrial Development Limited
• Original Assignee: Ramot University Authority For Applied Research and Industrial Development Limited
• Inventors: Schechter, Amir, Akselrod, Solange
• Primary Examiner(s): Nasser, Robert L.
• Application Number:
  US09/473,652
• Time in Patent Office: 608 Days
• Field of Search: 600/485, 600/500, 600/513, 600/504, 600/479
• US Class Current: 600/485
• CPC Class Codes: A61B 5/02416 using photoplethysmograph signals, e.g. generated by infrared radiation A61B5/14552 takes precedence
• CPC Class Codes: A61B 5/6826 Finger
• CPC Class Codes: A61B 5/6838 Clamps or clips

Abstract

A system for non-invasively monitoring at least one hemodynamic vascular parameter of an individual is disclosed. The system comprises (a) at least two infrared detectors being positionable in a spaced apart configuration against a region of a skin of the individual above at least one blood vessel, each of said at least two infrared detectors being for individually collecting infrared spectral data from said region of the skin, said infrared spectral data corresponding to a volume of blood present within said at least one blood vessel; and (b) a processing unit being in communication with said at least two infrared detectors, said processing unit being for independently processing said infrared spectral data collected by each of said at least two infrared detectors so as to yield information pertaining to the at least one hemodynamic vascular parameter of the individual.

Claims

1. A system for non-invasively monitoring at least one hemodynamic vascular parameter of an individual, the system comprising:

(a) at least two infrared detectors being positionable in a spaced apart configuration against a region of a skin of the individual above at least one blood vessel, each of said at least two infrared detectors being for individually collecting infrared spectral data from said region of the skin, said infrared spectral data corresponding to a volume of blood present within said at least one blood vessel; and

(b) a processing unit being in communication with said at least two infrared detectors, said processing unit being for independently processing said infrared spectral data collected by each of said at least two infrared detectors, said processing unit implementing an algorithm serving to account for blood reflection waves resulting from reflection sites in blood vessels, so as to yield information pertaining to the at least one hemodynamic vascular parameter of the individual.

2. The system of claim 1, wherein each of said at least two infrared detectors detects changes in infrared reflection from said region of said skin.

3. The system of claim 1, wherein each of said at least two infrared detectors includes an infrared source for irradiating said region of said skin and an infrared sensor for sensing infrared reflection reflected from said region of the skin.

4. The system of claim 3, wherein said infrared source irradiates said region with infrared radiation of a wavelength within a range of 800 nm to 960 nm.

5. The system of claim 1, wherein each of said at least two infrared detectors is an infrared photoplethysmograph.

6. The system of claim 1, wherein said at least two infrared detectors include three detectors each independently being for collecting infra red spectral emission data from said region, said three detectors being positionable in a spaced apart configuration against said region of said skin.

7. The system of claim 1, wherein the at least one hemodynamic vascular parameter is selected from the group consisting of blood viscosity, blood density, a radius of said blood vessel, an elasticity of said blood vessel, systolic blood pressure, diastolic blood pressure and continuous blood pressure.

8. The system of claim 1, wherein said infra red spectral data is collected by each of said at least two infrared detectors over the course of at least one heart beat cycle.

9. The system of claim 1, wherein said infra red spectral data is continuously collected by each of said at least two infrared detectors, thus enabling continuous monitoring of the at least one hemodynamic vascular parameter.

10. The system of claim 1, further comprising a device being for obstructing flow in said blood vessel down stream from said region of said skin.

11. The system of claim 1, further comprising an interface communicating with said processing unit, said interface being for providing information pertaining to the at least one hemodynamic vascular parameter to an operator of the system.

12. The system of claim 11, wherein said information pertaining to the at least one hemodynamic vascular parameter is provided to said operator in at least one format selected from the group consisting of a textual format, a graphic format and an audio format.

13. The system of claim 1, wherein said algorithm calculates said information pertaining to the at least one hemodynamic vascular parameter of the individual by determining a wave propagation velocity, a reflection coefficient and a distance to a reflection site.

14. The system of claim 1, wherein said algorithm calculates said information pertaining to the at least one hemodynamic vascular parameter of the individual by extracting values pertaining to displacement of a vessel wall under an assumption that a reflection coefficient is constant with respect to a frequency of a specific harmonic.

15. The system of claim 1, wherein said algorithm calculates said information pertaining to the at least one hemodynamic vascular parameter of the individual taking into account information pertaining to a foot to foot speed and calculating a wall displacement in order to calculate a forward propagating wave.

16. The system of claim 1, wherein said algorithm calculates said information pertaining to the at least one hemodynamic vascular parameter of the individual by extracting values pertaining to wall displacement and blood flow.

17. A method of non-invasively monitoring at least one hemodynamic vascular parameter of an individual, the method comprising:

(a) positioning at least two infrared detectors in a spaced apart configuration against a region of a skin of the individual above at least one blood vessel;

(b) individually collecting in each of said infrared detectors, infrared spectral data from said region of the skin, said infrared spectral data corresponding to a volume of blood present within said at least one blood vessel; and

(b) independently processing said infrared spectral data collected by each of said at least two infrared detectors, while accounting for blood reflection waves resulting from reflection sites in blood vessels, so as to yield information pertaining to the at least one hemodynamic vascular parameter of the individual.

18. The method of claim 17, wherein each of said at least two infrared detectors includes an infrared source for irradiating said region of said skin and an infrared sensor for sensing infrared reflection reflected from said region of the skin.

19. The method of claim 18, wherein said infrared source irradiates said region with infrared radiation of a wavelength within a range of 800 nm to 960 nm.

20. The method of claim 17, wherein each of said at least two infrared detectors is an infrared photoplethysmograph.

21. The method of claim 17, wherein said at least two infrared detectors include three detectors each independently being for collecting infra red spectral emission data from said region, said three detectors being positionable in a spaced apart configuration against said region of said skin.

22. The method of claim 17, wherein said at least one blood vessel includes an artery underlying said region of said skin.

23. The method of claim 17, wherein the at least one hemodynamic vascular parameter is selected from the group consisting of blood viscosity, blood density, a radius of said blood vessel, an elasticity of said blood vessel, systolic blood pressure, diastolic blood pressure and continuous blood pressure.

24. The method of claim 17, wherein said step of individually collecting in each of said infrared detectors, infrared spectral data from said region of the skin, is effected over the course of at least one heart beat cycle.

25. The method of claim 17, wherein said step of individually collecting in each of said infrared detectors, infrared spectral data from said region of the skin, is effected continuously thus enabling continuous monitoring of the at least one hemodynamic vascular parameter.

26. The method of claim 17, further comprising the step of obstructing flow in said blood vessel down stream from said region of said skin prior to said step of collecting in each of said infrared detectors, infrared spectral data from said region of the skin.

27. The method of claim 17, wherein accounting for blood reflection waves resulting from reflection sites in blood vessels is by determining a wave propagation velocity, a reflection coefficient and a distance to a reflection site.

28. The method of claim 17, wherein accounting for blood reflection waves resulting from reflection sites in blood vessels is by extracting values pertaining to motion of a vessel wall under an assumption that a reflection coefficient is constant with respect to a frequency of a specific harmonic.

29. The method of claim 17, wherein accounting for blood reflection waves resulting from reflection sites in blood vessels is by calculations taking into account information pertaining to a foot to foot speed and calculating a wall displacement in order to calculate a forward propagating wave.

30. The method of claim 17, wherein accounting for blood reflection waves resulting from reflection sites in blood vessels is by extracting values pertaining to wall displacement and blood flow.