Method and apparatus for non-invasive blood constituent monitoring

• US 6,181,958 B1
• Filed: 02/05/1999
• Issued: 01/30/2001
• Est. Priority Date: 02/05/1998
• Status: Expired due to Term

• Current Assignee: Hema Metrics, LLC (Fresenius SE & Co. KGaA)
• Original Assignee: In-Line Diagnostics Corp.
• Inventors: Miller, David R., Steuer, Robert R.
• Primary Examiner(s): WINAKUR, ERIC FRANK
• Application Number:
  US09/244,756
• Time in Patent Office: 725 Days
• Field of Search: 600/310, 600/322, 600/323, 600/326, 600/328, 600/330, 600/336
• US Class Current: 600/322
• CPC Class Codes: A61B 5/14532 for measuring glucose, e.g. by tissue impedance measurement
• CPC Class Codes: A61B 5/14535 for measuring haematocrit
• CPC Class Codes: A61B 5/14552 Details of sensors specially adapted therefor
• 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

Abstract

A system for determining a biologic constituent including hematocrit transcutaneously, noninvasively and continuously. A finger clip assembly includes 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 one predetermined wavelength of light is passed onto or through body tissues such as a finger, earlobe, or scalp, etc. and attenuation of light at that wavelength is detected. Likewise, the change in blood flow is determined by various techniques including optical, pressure, piezo and strain gage methods. Mathematical manipulation of the detected values compensates for the effects of body tissue and fluid and determines the hematocrit value. If an additional wavelength of light is used which attenuates light substantially differently by oxyhemoglobin and reduced hemoglobin, then the blood oxygen saturation value, independent of hematocrit may be determined. Further, if an additional wavelength of light is used which greatly attenuates light due to bilirubin (440 nm) or glucose (1060 nm), then the bilirubin or glucose value may also be determined. Also how to determine the hematocrit with a two step DC analysis technique is provided. 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 biological constituent concentration of the blood of a patient, the blood flowing in a pulsatile fashion in a body part of the patient so as to be subjectable to transcutaneous examination in the body part, the body part defining a blood conduit and the method comprising the steps of:

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

(b) directing radiation into the flowing blood within the blood conduit using a radiation generator situated within said blood conduit receiver, said radiation defining a directed radiation comprising a first quantity of radiation at a chosen radiation wavelength which, when directed into the flowing blood within the blood conduit,

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

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

(c) detecting the portion of said directed radiation which passes through both the blood conduit and the flowing blood therein using a radiation detector situated within said blood conduit receiver, said detected portion of said directed radiation comprising a second quantity of radiation at the chosen radiation wavelength; and

(d) detecting energy from the flowing blood within the blood conduit using an energy transducer situated within said blood conduit receiver, said energy transducer for measuring the time rate of change of blood volume, said energy defining a transduced energy comprising a quantity of energy which when detected from the flowing blood within the blood conduit, has a value which varies with the normalized change of the pulsatile blood; and

(e) operating exclusively on the second quantity of the radiation and the transduced energy to determine the desired biologic constituent concentration.

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

(a) determining the 1 intensity of the radiation wavelength; and

(b) determining a radiation wavelength pulsatile value representing the intensities of a pulsatile component of the radiation wavelength at discreet time intervals during the pulse.

3. A method as defined in claim 1, wherein the step of detecting the transduced energy comprises the steps of:

(a) determining the electronic signal generated from the transduced energy; and

(b) determining a transduced energy pulsatile value representing the intensities of a pulsatile component of the transduced energy at discreet time intervals during the pulse.

4. A method as defined in claim 1, wherein the step of operating exclusively on the second quantities of the radiation at the radiation wavelength to determine the desirers biologic constituent concentration of the patient comprises the steps of:

(a) mathematically operating on the second quantity of the radiation such that the time derivative of the pulsatile intensities is normalized by the average intensity over the pulse interval followed by a distance derivative of that quantity to produce a value proportional to ∂

α

/∂

t; and

(b) mathematically operating on the second quantity of the radiation such that the logarithm of the intensity is distance differentiated to produce the value α

.

5. A method as defined in claim 1, wherein the step of operating exclusively on the transduced energy comprises the step of performing the time derivative of the normalized pulsatile transduced energy to obtain the value ∂

X_b∂

t, where X_b is the fractional volume of blood per total tissue volume and t is time.

6. A method as defined in claim 1, wherein the step of operating exclusively on the second quantity of the radiation and the transduced energy comprises the step of mathematically solving the relationship K_b=B·

(α

·

∂

α

/∂

t)/(∂

X_b/∂

t) with a polynomial function or empirically determined value, where K_b is the macroscopic absorption coefficient for whole blood, α

is the bulk attenuation coefficient of the tissue sample, t is time, and X_b is the fractional volume of blood per total tissue volume.

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

8. A method as defined in claim 1, wherein the first attenuation value is substantially the same amount for oxyhemoglobin and for reduced hemoglobin in the flowing blood and the second attenuation value is at least ten items smaller than said first attenuation value for any competing constituent in the flowing blood.

9. A method as defined in claim 1, wherein the radiation wavelength is in the range from about 790 nanometers to 850 nanometers.

10. A method as defined in claim 1, wherein the radiation wavelength is in the range from about 550 nanometers to 600 nanometers.

11. A method as defined in claim 1, wherein the energy transducer means is a pressure transducer element, a strain gage element, a piezo electric film element, or a doppler detection element.

12. A method for determining a desired biological constituent concentration of the blood of a patient, the blood flowing in a pulsatile fashion in a body part of the patient so as to be subjectable to transcutaneous examination in the body part, the body part defining a blood conduit and the method comprising the steps of:

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

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

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

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

(B) has a second attenuation value which varies with the concentration of components other than the desired biologic constituent in the flowing blood, which second attenuation value is at least ten times smaller than said first attenuation 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 attenuation value which for varying concentrations in the flowing blood of the desired blood constituent is a non-fixed multiple of said first attenuation value; and

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

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

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

,

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

(d) detecting energy from the flowing blood within the blood conduit using an energy transducer situated within said blood conduit receiver, said energy transducer for measuring the time rate of change of blood volume, said energy defining a transduced energy comprising a quantity of energy which when detected from the flowing blood within the blood conduit, has a value which varies with the normalized blood change of the pulsatile blood; and

(e) operating exclusively on the second quantities of the radiations and the transduced energy to determine the desired biologic constituent concentration.

13. A method as defined in claim 12, wherein the step of operating exclusively on the transduced energy comprises the step of performing the time derivative of the normal pulsatile transduced energy of the second radiation wavelength to obtain the value ∂

X_b/∂

t, which is the time rate of change of blood volume.

14. A method as defined in claim 12, wherein the step of operating exclusively on the second quantities of the radiations and the transduced energy comprises the step of solving the relationship ƒ

(H)=G (α

^·

∂

α

/α

t) for the first wavelength divided by (α

^·

∂

α

/∂

t) for the second wavelength with a polynomial function or empirically determined value, where H is hematocrit, G is a constant related to bulk tissue absorption and scattering, α

is the bulk attenuation coefficient of a tissue sample, and t is time.

15. A method for determining a desired biological constituent concentration of the blood of a patient, the blood flowing in a pulsatile fashion in a body part of the patient so as to be subjectable to transcutaneous examination in the body part, the body part defining a blood conduit and the method comprising the steps of:

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

(b) directing radiation into the flowing blood within the blood conduit using a radiation generator situated within said blood conduit receiver, said radiation defining a directed radiation comprising a first quantity of radiation at a chosen radiation wavelength which, when directed into the flowing blood within the blood conduit,

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

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

(c) detecting the portion of said directed radiation which passes through both the blood conduit and the flowing blood therein using a radiation detector situated within said blood conduit receiver, said detected portion of said directed radiation comprising a second quantity of radiation at the chosen radiation wavelength; and

(d) detecting energy from the flowing blood within the blood conduit using an energy transducer situated within said blood conduit receiver, said energy transducer for measuring the time rate of change of blood volume, said energy defining a transduced energy comprising a quantity of energy which when detected from the flowing blood within the blood conduit, has a value which varies with the normalized blood volume; and

(e) operating exclusively on the second quantity of the radiation and the transduced energy to determine the desired biologic constituent concentration.

16. A method as defined in claim 15, wherein the step of operating exclusively on the transduced energy comprises the step of measuring the transduced energy when the blood conduit is blood-filled, then later made blood-less in order to obtain the value X_b, which is the volume of blood per total tissue volume.

17. A method as defined in claim 16, wherein the step of determining X_b is accomplished by solving (V_o/_ƒ

)−

1 where V_o is the volume of a bloodless finger and V_ƒ

is the volume of a blood filled finger.

18. A method as defined in claim 16, wherein the step of determining, X_b is accomplished by solving (V_o/V_ƒ

)−

1 with a polynomial function and the energy transducer is a pressure transducer and where V_o is the volume of a bloodless finger and V_ƒ

is the volume of a blood filled finger.

19. 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 so as to be subjectable to transcutaneous examination in the body part, the body part defining a blood conduit and the method of comprising the steps of:

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

(b) directing radiation into the flowing blood within the blood conduit using a radiation generator situated within said blood conduit receiver, said radiation defining a directed radiation comprising a first quantity of a radiation at a chosen radiation wavelength which, when directed into the flowing blood within the blood conduit,

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

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

(c) detecting the portion of said directed radiation which passes through both the blood conduit and the flowing blood therein using a radiation detector situated within said blood conduit receiver, said detected portion of said directed radiation comprising a second quantity of radiation at the chosen radiation wavelength;

(d) detecting energy from the flowing blood within the blood conduit using an energy transducer situated within said blood conduit receiver, said energy transducer for measuring the time rate of change of blood volume, said energy defining a transduced energy comprising a quantity of energy which when detected from the flowing blood within the blood conduit, has a value which varies with the normalized change of the pulsatile blood; and

(e) operating exclusively on the second quantity of the radiation and the transduced energy to determine the desired biologic constituent concentration by quantifying the tissue'"'"'s homogeneity from the linearity of the distance differentiation.

20. A method as defined in claim 19, wherein the step of operating exclusively on the second quantity of the radiation at the radiation wavelength to determine the desired biologic constituent concentration of the patient comprises the steps of:

(a) mathematically operating on the second quantity of the radiation wavelength such that the logarithm of the intensity is distance differentiated to produce the value α

;

(b) mathematically operating on the second quantity of the radiation wavelength such that the time derivative of the pulsatile intensities is normalized by the average intensity over the pulse interval followed by a distance derivative of that quantity to produce a value proportional to ∂

α

/∂

t;

which is the change in the bulk attenuation coefficient over time;

(c) mathematically determining the linearity and deviation of the logarithm of the intensity and the (∂

i/∂

t)/i values versus distance where i is light intensity and t is time; and

(d) mathematically decoupling, isolating, and determining the individual constituent absorptive and scattering coefficients from the values of a (the bulk attenuation coefficient), ∂

α

/∂

t and ∂

X_b/∂

t (the change in blood volume over time).