System and method for noninvasive hematocrit monitoring

• US 5,372,136 A
• Filed: 02/01/1993
• Issued: 12/13/1994
• Est. Priority Date: 10/06/1990
• Status: Expired due to Term

• Current Assignee: Fresenius Medical Care Holdings Incorporated (Fresenius Medical Care AG)
• Original Assignee: Non-invasive Medical Technologies
• Inventors: Harris, David H., Steuer, Robert R.
• Primary Examiner(s): Sykes, Angela D.
• Application Number:
  US08/011,882
• Time in Patent Office: 680 Days
• Field of Search: 128/633-634, 128/664-667, 356/39-41
• US Class Current: 600/326
• CPC Class Codes: A61B 5/14535 for measuring haematocrit
• CPC Class Codes: A61B 5/14546 for measuring analytes not otherwise provided for, e.g. ions, cytochromes
• CPC Class Codes: A61B 5/14551 for measuring blood gases
• CPC Class Codes: A61B 5/14552 Details of sensors specially adapted therefor
• CPC Class Codes: A61B 5/14557 specially adapted to extracorporeal circuits
• CPC Class Codes: A61B 5/6826 Finger
• CPC Class Codes: A61B 5/6838 Clamps or clips
• CPC Class Codes: A61B 5/6843 Monitoring or controlling sensor contact pressure
• CPC Class Codes: A61M 1/361 before treatment
• CPC Class Codes: A61M 1/3612 after treatment
• CPC Class Codes: B07C 3/00 Sorting according to destination collating the pages of a book B42C1/00
• CPC Class Codes: G01N 2021/036 transformable, modifiable
• CPC Class Codes: G01N 21/0303 Optical path conditioning in cuvettes, e.g. windows; adapted optical elements or systems; path modifying or adjustment G01N21/031 - G01N21/15 take precedence

Abstract

A system for determining the hematocrit transcutaneously and noninvasively. Disclosed are a finger clip assembly and an earlobe clip assembly, each including at least a pair of emitters and a photodiode in appropriate alignment to enable operation in either a transmissive mode or a reflectance mode. At least two, and preferably three, predetermined wavelengths of light are passed onto or through body tissues such as the finger, earlobe, or scalp, etc. and the extinction of each wavelength is detected. Mathematical manipulation of the detected values compensates for the effects of body tissue and fluid and determines the hematocrit value. If a fourth wavelength of light is used which is extinguished substantially differently by oxyhemoglobin and reduced hemoglobin and which is not substantially extinguished by plasma, then the blood oxygen saturation value, independent of hematocrit, may be determined.

It is also disclosed how to detect and analyze multiple wavelengths using a logarithmic DC analysis technique. Then a pulse wave is not required so, this method may be utilized in states of low blood pressure or low blood flow.

Claims

1. A method for determining a desired biologic constituent concentration of the blood of a patient, the blood flowing in a pulsatile fashion in a body part of the patient or in an extracorporeal passageway in communication with the circulatory system of the patient so as to be subjectable to transcutaneous examination in the body part or to noninvasive examination in the extracorporeal passageway, the body part and the extracorporeal passageway defining a blood conduit and the method comprising the steps of:

(a) placing the blood conduit within a blood conduit receiving means with the blood flowing in the blood conduit;

(b) directing radiation into the flowing blood within the blood conduit using a radiation generation means situated within said blood conduit receiving means, said radiation defining a directed radiation comprising;

(i) a first quantity of a radiation at a first radiation wavelength which, when directed into the flowing blood within the blood conduit,

(A) has a first extinguishment value which varies with the desired biologic constituent concentration in the flowing blood and

(B) has a second extinguishment value which varies with the concentration of components other than the desired biologic constituent in the flowing blood, which second extinguishment value is at least ten times smaller than said first extinguishment value; and

(ii) a first quantity of a radiation at a second radiation wavelength, distinct from said first wavelength, which, when directed into the flowing blood within the blood conduit,

(A) has a third extinguishment value which for varying concentrations in the flowing blood of the desired blood constituent is a non-fixed multiple of said first extinguishment value and

(B) has a fourth extinguishment value which varies with the concentration of components other than the desired biologic constituent in the flowing blood, which fourth extinguishment value is at least ten times greater than said second extinguishment value;

(c) detecting the portion of said directed radiation which passes through both the blood conduit and the flowing blood therein using a radiation detection means situated within said blood conduit receiving means, said detected portion of said directed radiation comprising;

(i) a second quantity of a radiation at the first radiation wavelength, and

(ii) a second quantity of a radiation at the second radiation wavelength;

(d) operating exclusively on the second quantities of the radiations at the first and second radiation wavelengths to determine the desired biologic constituent concentration.

2. A method as defined in claim 1, wherein the step of detecting the second quantity of the first radiation wavelength comprises the steps of:

(a) determining the intensity of the total first radiation wavelength;

(b) determining a first radiation wavelength pulsatile value representing the difference between the maximum and the minimum intensity of a pulsatile component of the first radiation wavelength;

(c) determining the ratio between the first radiation wavelength pulsatile value and the intensity of the total first radiation wavelength over a period of time; and

(d) determining a first mean ratio value over a period of time of the ratio between the first radiation wavelength pulsatile component and the average intensity of the first radiation wavelength.

3. A method as defined in claim 2, wherein the step of detecting the second quantity of the second radiation wavelength comprises the steps of:

(a) determining the intensity of the total second radiation wavelength;

(b) determining a second radiation wavelength pulsatile value representing the difference between the maximum and the minimum intensity of a pulsatile component of the second radiation wavelength;

(c) determining the ratio between the second radiation wavelength pulsatile value and the intensity of the total second radiation wavelength over a period of time;

(d) determining a second mean ratio value over a period of time of the ratio between the second radiation wavelength pulsatile component and the average intensity of the second radiation wavelength; and

(e) wherein the step of operating to determine the desired biologic constituent concentration of the patient by operating exclusively on the second quantities of the first and second radiation wavelengths comprises the step of determining the desired biologic constituent concentration of the patient by the ratio between the first mean ratio value and the second mean ratio value.

4. A method as defined in claim 1, wherein the step of detecting the second quantity of the first radiation wavelength comprises the steps of:

(a) determining the intensity of the total first radiation wavelength;

(b) determining a first radiation wavelength pulsatile value representing the true time derivative of a pulsatile component of the first radiation wavelength;

(c) determining the ratio between the first radiation wavelength pulsatile value and the intensity of the total first radiation wavelength over a period of time; and

(d) determining a first mean ratio value over a period of time of the ratio between the first radiation wavelength pulsatile component and the average intensity of the first radiation wavelength.

5. A method as defined in claim 4, wherein the step of detecting the second quantity of the second radiation wavelength comprises the steps of:

(a) determining the intensity of the total second radiation wavelength;

(b) determining a second radiation wavelength pulsatile value representing the true time derivative of a pulsatile component of the second radiation wavelength;

(c) determining the ratio between the second radiation wavelength pulsatile value and the intensity of the total second radiation wavelength over a period of time;

(d) determining a second mean ratio value over a period of time of the ratio between the second radiation wavelength pulsatile component and the average intensity of the second radiation wavelength; and

(e) wherein the step of operating to determine the desired biologic constituent concentration of the patient by operating exclusively on the second quantities of the first and second radiation wavelengths comprises the step of determining the desired biologic constituent concentration of the patient by the ratio between the first mean ratio value and the second mean ratio value.

6. A method as defined in claim 1, wherein the step of operating exclusively on the second quantities of the radiations at the first and second radiation wavelengths to determine the desired biologic constituent concentration of the patient comprises the step of associating the second quantities of the first and second radiation wavelengths with an empirically obtained value.

7. A method as defined in claim 1, wherein the step of operating exclusively on the second quantities of the radiations at the first and second radiation wavelengths to determine the desired biologic constituent concentration of the patient comprises the step of mathematically manipulating the second quantities of the first and second radiation wavelengths with a polynomial function to obtain a desired biologic constituent value.

8. A method as defined in claim 1, wherein the desired biologic constituent comprises red blood cells.

9. A method as defined in claim 1, wherein the desired biologic constituent comprises hematocrit.

10. A method as defined in claim 1, wherein the desired biologic constituent comprises hemoglobin.

11. A method as defined in claim 1, wherein the first extinguishment value is substantially the same amount for oxyhemoglobin and for reduced hemoglobin in the flowing blood and the second extinguishment value is at least ten times smaller than said first extinguishment value for the plasma in the flowing blood.

12. A method as defined in claim 1, wherein the first radiation wavelength is in the range from about 780 nanometers to about 850 nanometers.

13. A method as defined in claim 1, wherein the first radiation wavelength is in the range from about 520 nanometers to about 600 nanometers.

14. A method as defined in claim 1, wherein the third extinguishment value is substantially the same amount for oxyhemoglobin and for reduced hemoglobin in the flowing blood and the fourth extinguishment value is approximately the same as said third extinguishment value for the plasma in the flowing blood.

15. A method as defined in claim 1, wherein the second radiation wavelength is in the range from about 1200 nanometers to about 1600 nanometers.

16. A method as defined in claim 15, wherein:

(a) said directed radiation further comprises a first quantity of a radiation at a fourth radiation wavelength, distinct from said first, second and third radiation wavelengths, which when directed into the flowing blood in the blood conduit,

(ii) has a seventh extinguishment value which varies substantially with the oxyhemoglobin and reduced hemoglobin concentrations in the flowing blood, and which

(ii) has an eighth extinguishment value, which is at least ten times smaller than said seventh extinguishment value for the plasma in the flowing blood;

(b) said detected portion of said directed radiation further comprises a second quantity of a radiation at the fourth radiation wavelength;

(c) and further comprising the steps of;

(i) mathematically operating on the second quantity of the fourth radiation wavelength such that the spatial, geometric, and tissue variations are eliminated in the fourth radiation wavelength;

(ii) determining a blood oxygen saturation value which is independent of hematocrit by mathematically operating on the second quantities of the first, second, third, and fourth radiation wavelengths.

17. A method as defined in claim 16, wherein the fourth radiation wavelength is in the range from about 600 nanometers to about 700 nanometers.

18. A method as defined in claim 1, wherein the flowing blood includes a competing biologic constituent relative to the hemoglobin in the blood, and wherein:

(a) said directed radiation in said step of directing radiation into the flowing blood within the blood conduit further comprises a first quantity of a radiation at a third radiation wavelength, distinct from said first and second radiation wavelengths, and which, when directed into the flowing blood in the blood conduit,

(i) has a fifth extinguishment value which varies with the competing biologic constituent concentration in the flowing blood, said fifth extinguishment value being at least five times greater than said second extinguishment value; and

(ii) has a sixth extinguishment value which varies with the concentration of components other than the competing biologic constituent concentration in the flowing blood;

(b) said detected portion of said directed radiation in said step of detecting further comprises a second quantity of a radiation at the third radiation wavelength;

(c) mathematically operating on the second quantities of the first, second, and third radiation wavelengths such that the spatial, geometric, and tissue variations are eliminated in each radiation wavelength; and

(d) mathematically operating on the second quantities of the first, second, and third radiation wavelengths to compensate for the effect of the competing biologic constituent.

19. A method as defined in claim 18, wherein the third radiation wavelength is extinguished approximately the same amount by oxyhemoglobin and reduced hemoglobin in the flowing blood and is substantially extinguished by plasma in the flowing blood.

20. A method as defined in claim 18, wherein the third radiation wavelength is in the range from about 900 nanometers to about 1000 nanometers.

21. A method as defined in claim 18, further comprising the steps of:

(a) said directed radiation in said step of directing radiation into the flowing blood within the blood conduit further comprises a first quantity of a radiation at a fourth radiation wavelength, distinct from said first, second and third radiation wavelengths, and which, when directed into the flowing blood in the blood conduit,

(i) has a seventh extinguishment value which varies substantially with the oxyhemoglobin and reduced oxyhemoglobin concentrations in the flowing blood, and which

(ii) has an eighth extinguishment value, which is at least ten times smaller than said seventh extinguishment value for the plasma in the flowing blood;

(b) said detected portion of said directed radiation in said step of detecting further comprises a second quantity of a radiation at the fourth radiation wavelength;

(c) and further comprising the steps of;

(i) mathematically operating on the second quantity of the fourth radiation wavelength such that the spatial, geometric, and tissue variations are eliminated in the fourth radiation wavelength;

(ii) determining a blood oxygen saturation value which is independent of hematocrit by mathematically operating on the second quantities of the first, second, third, and fourth radiation wavelengths.

22. A method as defined in claim 21, wherein the fourth radiation wavelength is in the range from about 600 nanometers to about 700 nanometers.

23. A method for determining the hematocrit of the blood of a patient, the blood flowing in a pulsatile fashion in a body part of the patient or in an extracorporeal passageway in communication with the circulatory system of the patient so as to be subjectable to transcutaneous examination in the body part or to noninvasive examination in the extracorporeal passageway, the body part and the extracorporeal passageway defining a blood conduit and the method comprising the steps of:

(a) placing the blood conduit within a blood conduit receiving means with the flowing blood in the blood conduit;

(b) directing radiation into the flowing blood within the blood conduit using a radiation generation means situated within the blood conduit receiving means, said radiation defining a directed radiation comprising;

(i) a first quantity of a radiation at a first radiation wavelength which, when directed into the flowing blood within the blood conduit,

(A) has a first extinguishment value which varies with the hematocrit in the flowing blood and

(B) has a second extinguishment value which varies with the plasma in the flowing blood, which second extinguishment value is at least ten times smaller than said first extinguishment value; and

(ii) a first quantity of radiation at a second radiation wavelength, distinct from said first wavelength, which, when directed into the flowing blood within the blood conduit,

(A) has a third extinguishment value which for varying hematocrit in the flowing blood is a non-fixed multiple of said first extinguishment value; and

(B) has a fourth extinguishment value which varies with the plasma in the flowing blood, which fourth extinguishment value is at least ten times greater than said second extinguishment value;

(c) detecting the portion of said directed radiation which passes through both the blood conduit and the flowing blood therein with a radiation detection means situated within said conduit receiving means, said detected portion of said directed radiation comprising;

(i) a second quantity of a radiation at the first radiation wavelength, and

(ii) a second quantity of a radiation at the second radiation wavelength;

(e) operating exclusively on the second quantities of the radiations at the first and second radiation wavelengths to determine the hematocrit of the patient.

24. A method as defined in claim 23, further comprising the step of displaying the hematocrit.

25. A method as defined in claim 23, wherein the step of operating exclusively on the second quantities of the radiations at the first and second radiation wavelengths to determine the hematocrit of the patient comprises the step of associating the second quantities of the first and second radiation wavelengths with an empirically obtained value.

26. A method as defined in claim 23, wherein the step of operating exclusively on the second quantities of the radiations at the first and second radiation wavelengths to determine the hematocrit of the patient comprises the step of mathematically manipulating the second quantities of the first and second radiation wavelengths with a polynomial function to obtain a hematocrit.

27. A method as defined in claim 23, wherein the first radiation wavelength is in the range from about 780 nanometers to about 850 nanometers.

28. A method as defined in claim 23, wherein the first radiation wavelength is in the range from about 520 nanometers to about 600 nanometers.

29. A method as defined in claim 23, wherein the second radiation wavelength is in the range from about 1200 nanometers to about 1600 nanometers.

30. A method as defined in claim 23, wherein the flowing blood includes a competing biologic constituent relative to the hemoglobin in the blood, and wherein:

(a) said directed radiation in said step of directing radiation into the flowing blood within the blood conduit further comprises a first quantity of a radiation at a third radiation wavelength, distinct from said first and second radiation wavelengths, and which, when directed into the flowing blood in the blood conduit,

(i) has a fifth extinguishment value which varies with the competing biologic constituent concentration in the flowing blood, said fifth extinguishment value being at least five times greater than said second extinguishment value; and

(ii) has a sixth extinguishment value which varies with the concentration of components other than the competing biologic constituent concentration in the flowing blood;

(b) said detected portion of said directed radiation in said step of detecting further comprises a second quantity of a radiation at the third radiation wavelength.

31. A method as defined in claim 30, further comprising the step of:

(a) operating on the second quantity of radiation at the third radiation wavelength and the hematocrit determined in said step of operating exclusively on the second quantities of the radiations at the first and second wavelengths to determine a corrected hematocrit of the patient; and

(b) displaying the corrected hematocrit of the patient.

32. A method as defined in claim 30, further comprising the step of varying the directed radiation on the basis of the detected portion of the directed radiation, thereby to maintain the detected portion of the directed radiation within a predetermined range.

33. A method as defined in claim 30, wherein the third radiation wavelength is in the range from 900 nanometers to 1000 nanometers.

34. A method as defined in claim 30, wherein:

(a) said directed radiation in said step of directing radiation into the flowing blood within the blood conduit further comprises a first quantity of a radiation at a fourth radiation wavelength, distinct from said first, second and third radiation wavelengths, and which, when directed into the flowing blood in the blood conduit,

(i) has a seventh extinguishment value which varies substantially with the oxyhemoglobin and reduced oxyhemoglobin concentrations in the flowing blood, and which

(ii) has an eighth extinguishment value, which is at least ten times smaller than said seventh extinguishment value for the plasma in the flowing blood,

(b) said detected portion of said directed radiation in said step of detecting further comprises a second quantity of a radiation at the fourth radiation wavelength.

35. A method as defined in claim 34, further comprising the steps of:

(a) determining a hematocrit independent blood oxygen saturation value by the second quantities of the first, second, third, and fourth radiation wavelengths; and

(b) displaying the hematocrit independent blood oxygen saturation value.

36. A method as defined in claim 35, wherein the fourth radiation wavelength is in the range from 600 nanometers to 700 nanometers.

37. A method as defined in claim 35, wherein the radiation generation means is situated opposite the radiation detection means, whereby the first, second, third, and fourth radiation wavelengths are transmitted through the blood conduit.

38. A method as defined in claim 35, wherein the radiation generation means is not situated opposite the radiation detection means, whereby the first, second, third, and fourth radiation wavelengths are reflected from the blood conduit.

40. A method as defined in claim 35, wherein the step of detecting the second quantity of the second radiation wavelength comprises the steps of:

(a) determining the extinguishment of the total second radiation wavelength;

(b) determining a second radiation wavelength pulsatile value representing the difference between the maximum and the minimum extinguishment of a pulsatile component of the second radiation wavelength;

(c) determining the ratio between the second radiation wavelength pulsatile value and the extinguishment of the total second radiation wavelength over a period of time;

(d) determining a second mean ratio value over a period of time of the ratio between the second radiation wavelength pulsatile component and the average extinguishment of the second radiation wavelength; and

(e) wherein the step of determining the hematocrit of the patient by operating on the second quantities of the first and second radiation wavelengths comprises the step of determining the hematocrit of the patient by the ratio between the first mean ratio value and the second mean ratio value.

39. A method for determining the hematocrit of the blood of a patient, the blood flowing in a pulsatile fashion in a body part of the patient or in an extracorporeal passageway in communication with the circulatory system of the patient so as to be subjectable to transcutaneous examination in the body part or to noninvasive examination in the extracorporeal passageway, the body part and the extracorporeal passageway defining a blood conduit and the method comprising the steps of:

(a) placing the blood conduit within a blood conduit receiving means with the flowing blood in the blood conduit;

(b) directing radiation into the flowing blood within the blood conduit using a radiation generation means situated within the blood conduit receiving means, said radiation defining a directed radiation comprising;

(i) a first quantity of a radiation at a first radiation wavelength which, when directed into the flowing blood within the blood conduit,

(A) is extinguished substantially the same amount by oxyhemoglobin and reduced hemoglobin in the flowing blood and

(B) is extinguished by the plasma in the flowing blood in a first manner; and

(ii) a first quantity of radiation at a second radiation wavelength which, when directed into the flowing blood within the blood conduit,

(A) is extinguished substantially the same amount by oxyhemoglobin and reduced hemoglobin in the flowing blood and

(B) is extinguished by the plasma in the flowing blood in a second manner substantially different from said first manner;

(c) detecting the portion of said directed radiation which passes through both the blood conduit and the flowing blood therein with a radiation detection means situated within said conduit receiving means, said detected portion of said directed radiation comprising;

(i) a second quantity of a radiation at the first radiation wavelength being detected by steps comprising;

(A) determining the extinguishment of the total first radiation wavelength;

(B) determining a first radiation wavelength pulsatile value representing the difference between the maximum and the minimum extinguishment of a pulsatile component of the first radiation wavelength;

(C) determining the ratio between the first radiation wavelength pulsatile value and the extinguishment of the total first radiation wavelength over a period of time; and

(D) determining a first mean ratio value over a period of time of the ratio between the first radiation wavelength pulsatile component and the average extinguishment of the first radiation wavelength, and

(ii) a second quantity of a radiation at the second radiation wavelength; and

(d) operating on the second quantities of the radiations at the first and second radiation wavelengths to determine the hematocrit of the patient.

41. A method for determining the hematocrit of the blood of a patient, the blood flowing in a pulsatile fashion in a body part of the patient or in an extracorporeal passageway in communication with the circulatory system of the patient so as to be subjectable to transcutaneous examination in the body part or to noninvasive examination in the extracorporeal passageway, the body part and the extracorporeal passageway defining a blood conduit and the method comprising the steps of:

(a) placing the blood conduit within a blood conduit receiving means with the flowing blood in the blood conduit;

(b) directing radiation into the flowing blood within the blood conduit using a radiation generation means situated within the blood conduit receiving means, said radiation defining a directed radiation comprising;

(i) a first quantity of a radiation at a first radiation wavelength which, when directed into the flowing blood within the blood conduit,

(A) is extinguished substantially the same amount by oxyhemoglobin and reduced hemoglobin in the flowing blood and

(B) is extinguished by the plasma in the flowing blood in a first manner; and

(ii) a first quantity of radiation at a second radiation wavelength which, when directed into the flowing blood within the blood conduit,

(A) is extinguished substantially the same amount by oxyhemoglobin and reduced hemoglobin in the flowing blood and

(B) is extinguished by the plasma in the flowing blood in a second manner substantially different from said first manner;

(c) detecting the portion of said directed radiation which passes through both the blood conduit and the flowing blood therein with a radiation detection means situated within said conduit receiving means, said detected portion of said directed radiation comprising;

(i) a second quantity of a radiation at the first radiation wavelength, and

(ii) a second quantity of a radiation at the second radiation wavelength being detected by steps comprising;

(A) determining the extinguishment of the total first radiation wavelength;

(B) determining a first radiation wavelength pulsatile value representing the true time derivative of a pulsatile component of the first radiation wavelength;

(C) determining the ratio between the first radiation wavelength pulsatile value and the extinguishment of the total first radiation wavelength over a period of time; and

(D) determining a first mean ratio value over a period of time of the ratio between the first radiation wavelength pulsatile component and the average extinguishment of the first radiation wavelength; and

(d) operating on the second quantities of the radiations at the first and second radiation wavelengths to determine the hematocrit of the patient.

42. A method as defined in claim 41, wherein the step of detecting the second quantity of the second radiation wavelength comprises the steps of:

(a) determining the extinguishment of the total second radiation wavelength;

(b) determining a second radiation wavelength pulsatile value representing the true time derivative of a pulsatile component of the second radiation wavelength;

(c) determining the ratio between the second radiation wavelength pulsatile value and the extinguishment of the total second radiation wavelength over a period of time;

(d) determining a second mean ratio value over a period of time of the ratio between the second radiation wavelength pulsatile component and the average extinguishment of the second radiation wavelength; and

(e) wherein the step of determining the hematocrit of the patient by operating on the second quantities of the first and second radiation wavelengths comprises the step of determining the hematocrit of the patient by the ratio between the first mean ratio value and the second mean ratio value.

43. A method for determining the hematocrit of the flowing blood of a patient, the flowing blood including a competing biologic constituent relative to the hemoglobin in the blood, the blood flowing in a pulsatile fashion in a body part of the patient or in an extracorporeal passageway in communication with the circulatory system of the patient so as to be subjectable to transcutaneous examination in the body part or to noninvasive examination in the extracorporeal passageway, the body part and the extracorporeal passageway defining a blood conduit and the method comprising the steps of:

(a) placing the blood conduit within a blood conduit receiving means with the flowing blood in the blood conduit;

(b) directing radiation into the flowing blood within the blood conduit using a radiation generation means situated within the blood conduit receiving means, said radiation defining a directed radiation comprising;

(i) a first quantity of a radiation at a first radiation wavelength which, when directed into the flowing blood within the blood conduit,

(A) is extinguished substantially the same amount by oxyhemoglobin and reduced hemoglobin in the flowing blood and

(B) is extinguished by the plasma in the flowing blood in a first manner;

(ii) a first quantity of radiation at a second radiation wavelength which, when directed into the flowing blood within the blood conduit,

(A) is extinguished substantially the same amount by oxyhemoglobin and reduced hemoglobin in the flowing blood and

(B) is extinguished by the plasma in the flowing blood in a second manner substantially different from said first manner; and

(iii) a first quantity of a radiation at a third radiation wavelength, which when directed into the flowing blood in the blood conduit,

(A) is extinguished by the competing biologic constituent in the flowing blood in a manner characteristic of the competing biologic constituent; and

(B) is extinguished by the constituents of the flowing blood other than the competing biologic constituent in a third manner, said third manner being substantially different from one of said first and second manners;

(c) detecting the portion of said directed radiation which passes through both the blood conduit and the flowing blood therein with a radiation detection means situated within said conduit receiving means, said detected portion of said directed radiation comprising;

(i) a second quantity of a radiation at the first radiation wavelength,

(ii) a second quantity of a radiation at the second radiation wavelength, and

(iii) a second quantity of a radiation at the third radiation wavelength being detected by steps comprising;

(A) determining the extinguishment of the total third radiation wavelength;

(B) determining a third radiation wavelength pulsatile value representing the difference between the maximum and the minimum extinguishment of a pulsatile component of the third radiation wavelength;

(C) determining the ratio between the third radiation wavelength pulsatile value and the extinguishment of the total third radiation wavelength over a period of time;

(D) determining a third mean ratio value over a period of time of the ratio between the third radiation wavelength pulsatile component and the average extinguishment of the third radiation wavelength; and

(d) operating on the second quantities of the radiations at the first and second and third radiation wavelengths to determine the corrected hematocrit of the patient by determining the hematocrit of the patient by the combination of the first, second, and third mean ratio values.

44. A method as defined in claim 43, wherein the first, second and third mean ratio values are combined linearly.

45. A method for determining the hematocrit of the flowing blood of a patient, the flowing blood including a competing biologic constituent relative to the hemoglobin in the blood, the blood flowing in a pulsatile fashion in a body part of the patient or in an extracorporeal passageway in communication with the circulatory system of the patient so as to be subjectable to transcutaneous examination in the body part or to noninvasive examination in the extracorporeal passageway, the body part and the extracorporeal passageway defining a blood conduit and the method comprising the steps of:

(a) placing the blood conduit within a blood conduit receiving means with the flowing blood in the blood conduit;

(b) directing radiation into the flowing blood within the blood conduit using a radiation generation means situated within the blood conduit receiving means, said radiation defining a directed radiation comprising;

(i) a first quantity of a radiation at a first radiation wavelength which, when directed into the flowing blood within the blood conduit,

(A) is extinguished substantially the same amount by oxyhemoglobin and reduced hemoglobin in the flowing blood and

(B) is extinguished by the plasma in the flowing blood in a first manner;

(ii) a first quantity of radiation at a second radiation wavelength which, when directed into the flowing blood within the blood conduit,

(A) is extinguished substantially the same amount by oxyhemoglobin and reduced hemoglobin in the flowing blood and

(B) is extinguished by the plasma in the flowing blood in a second manner substantially different from said first manner; and

(iii) a first quantity of a radiation at a third radiation wavelength, which when directed into the flowing blood in the blood conduit,

(A) is extinguished by the competing biologic constituent in the flowing blood in a manner characteristic of the competing biologic constituent; and

(B) is extinguished by the constituents of the flowing blood other than the competing biologic constituent in a third manner, said third manner being substantially different from one of said first and second manners;

(c) detecting the portion of said directed radiation which passes through both the blood conduit and the flowing blood therein with a radiation detection means situated within said conduit receiving means, said detected portion of said directed radiation comprising;

(i) a second quantity of a radiation at the first radiation wavelength,

(ii) a second quantity of a radiation at the second radiation wavelength, and

(iii) a second quantity of a radiation at the third radiation wavelength being detected by steps comprising;

(A) determining the extinguishment of the total third radiation wavelength;

(B) determining a third radiation wavelength pulsatile value representing the true time derivative of a pulsatile component of the third radiation wavelength;

(C) determining the ratio between the third radiation wavelength pulsatile value and the extinguishment of the total third radiation wavelength over a period of time;

(D) determining a third mean ratio value over a period of time of the ratio between the third radiation wavelength pulsatile component and the average extinguishment of the third radiation wavelength; and

(d) operating on the second quantities of the radiations at the first and second and third radiation wavelengths to determine the corrected hematocrit of the patient by determining the hematocrit of the patient by the combination of the first, second, and third mean ratio values.

46. A method as defined in claim 45, wherein the first, second, and third mean ratio values are combined linearly.

47. A method for determining the hematocrit of the flowing blood of a patient, the flowing blood including a competing biologic constituent relative to the hemoglobin in the blood, the blood flowing in a pulsatile fashion in a body part of the patient or in an extracorporeal passageway in communication with the circulatory system of the patient so as to be subjectable to transcutaneous examination in the body part or to noninvasive examination in the extracorporeal passageway, the body part and the extracorporeal passageway defining a blood conduit and the method comprising the steps of:

(a) placing the blood conduit within a blood conduit receiving means with the flowing blood in the blood conduit;

(b) directing radiation into the flowing blood within the blood conduit using a radiation generation means situated within the blood conduit receiving means, said radiation defining a directed radiation comprising;

(i) a first quantity of a radiation at a first radiation wavelength which, when directed into the flowing blood within the blood conduit,

(A) is extinguished substantially the same amount by oxyhemoglobin and reduced hemoglobin in the flowing blood and

(B) is extinguished by the plasma in the flowing blood in a first manner;

(ii) a first quantity of radiation at a second radiation wavelength which, when directed into the flowing blood within the blood conduit,

(A) is extinguished substantially the same amount by oxyhemoglobin and reduced hemoglobin in the flowing blood and

(B) is extinguished by the plasma in the flowing blood in a second manner substantially different from said first manner;

(iii) a first quantity of a radiation at a third radiation wavelength, which when directed into the flowing blood in the blood conduit,

(A) is extinguished by the competing biologic constituent in the flowing blood in a manner characteristic of the competing biologic constituent; and

(B) is extinguished by the constituents of the flowing blood other than the competing biologic constituent in a third manner, said third manner being substantially different from one of said first and second manners; and

(iv) a first quantity of a radiation at a fourth radiation wavelength, distinct from said first, second and third radiation wavelengths, and which, when directed into the flowing blood within the blood conduit,

(A) is extinguished substantially differently by oxyhemoglobin and by reduced oxyhemoglobin in the flowing blood, and which

(B) is not substantially extinguished by the plasma in the flowing blood;

(c) detecting the portion of said directed radiation which passes through both the blood conduit and the flowing blood therein with a radiation detection means situated within said conduit receiving means, said detected portion of said directed radiation comprising;

(i) a second quantity of a radiation at the first radiation wavelength,

(ii) a second quantity of a radiation at the second radiation wavelength,

(iii) a second quantity of a radiation at the third radiation wavelength, and

(iv) a second quantity of a radiation at the fourth radiation wavelength;

(d) operating on the second quantities of the radiations at the first and second radiation wavelengths to determine the hematocrit of the patient;

(e) determining the blood oxygen content value by the second quantities of the first, second, third, and fourth radiation wavelengths; and

(f) displaying the blood oxygen content value.

48. A method for determining the hematocrit of the blood of a patient, the blood flowing in a pulsatile fashion in a body part of the patient or in an extracorporeal passageway in communication with the circulatory system of the patient so as to be subjectable to transcutaneous examination in the body part or to noninvasive examination in the extracorporeal passageway, the body part and the extracorporeal passageway defining a blood conduit and the method comprising the steps of:

(a) placing the blood conduit within a blood conduit receiving means with the flowing blood in the blood conduit;

(b) directing radiation into the flowing blood within the blood conduit using a radiation generation means situated within the blood conduit receiving means, said radiation defining a directed radiation comprising;

(i) a first quantity of a radiation at a first radiation wavelength which, when directed into the flowing blood within the blood conduit,

(A) is extinguished substantially the same amount by oxyhemoglobin and reduced hemoglobin in the flowing blood and

(B) is extinguished by the plasma in the flowing blood in a first manner; and

(ii) a first quantity of radiation at a second radiation wavelength which, when directed into the flowing blood within the blood conduit,

(A) is extinguished substantially the same amount by oxyhemoglobin and reduced hemoglobin in the flowing blood and

(B) is extinguished by the plasma in the flowing blood in a second manner substantially different from said first manner;

(c) detecting the portion of said directed radiation which passes through both the blood conduit and the flowing blood therein with a radiation detection means situated within said conduit receiving means, said detected portion of said directed radiation comprising;

(i) a second quantity of a radiation at the first radiation wavelength, and

(ii) a second quantity of a radiation at the second radiation wavelength;

(d) operating on the second quantities of the radiations at the first and second radiation wavelengths to determine the hematocrit of the patient by determining the logarithmic intensity ratio of the second quantities of the first and the second radiation wavelengths.