# US 6,819,950 B2 · Method for noninvasive continuous determination of physiologic characteristics

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- Number: US 6,819,950 B2
- Document ID: US6819950B2
- Status: Granted
- Kind: B2
- Application number: 10/008,245
- Filed: 2001-11-07
- Published: 2003-06-12
- Granted: 2004-11-16
- Earliest claimed: 2000-10-06
- Inventors: Alexander K. Mills
- Web page: https://patentgrep.com/patent/US6819950B2

## CPC

- A61B 5/6826: {Finger}
- A61B 5/02028: {Determining haemodynamic parameters not otherwise provided for, e.g. cardiac contractility or left ventricular ejection fraction}
- A61B 5/0205: Simultaneously evaluating both cardiovascular conditions and different types of body conditions, e.g. heart and respiratory condition
- A61B 5/02055: {Simultaneously evaluating both cardiovascular condition and temperature}
- A61B 5/02125: {of pulse wave propagation time}
- A61B 5/0285: Measuring or recording phase velocity of blood waves
- A61B 5/14539: {for measuring pH}
- A61B 5/14546: {for measuring analytes not otherwise provided for, e.g. ions, cytochromes}
- A61B 5/14551: {for measuring blood gases}
- A61B 5/14552: {Details of sensors specially adapted therefor}
- A61B 5/318: Heart-related electrical modalities, e.g. electrocardiography [ECG]
- A61B 5/6838: {Clamps or clips}
- A61B 5/021: Measuring pressure in heart or blood vessels
- A61B 5/029: Measuring blood output from the heart, e.g. minute volume
- A61B 5/14532: {for measuring glucose, e.g. by tissue impedance measurement}
- A61B 2560/0261: using hydrostatic pressure
- A61B: DIAGNOSIS; SURGERY; IDENTIFICATION (usefulness limited to only animals A61D)

## Abstract

The invention comprises methods for noninvasively monitoring physiological characteristics of a patient's blood. Determinations of blood constituent concentrations may be made by comparing absorbance of radiation at varying parameters, such as path length and blood pressure. Preferably, changes in pressure are effected by changing the height of the probes relative to the patient's heart. Determinations of blood pH may be made by comparing absorbance of the blood at different wavelengths. The temperature of the blood, and thus of the patient's core, may also be accurately determined. Further, cardiac output characteristics and blood pressures may be noninvasively determined using the methods of the invention.

## Claims

### Claim 1

A method for noninvasively determining the concentration of a blood constituent comprising the steps of:
providing a tissue probe, said tissue probe including a first radiation emitter adapted to emit radiation having a first wavelength and a first radiation detector adapted to receive said radiation after absorbance through a radiation path length of a patient's blood;
measuring absorbance of said patient's blood by transmitting said radiation at said first wavelength through said patient's blood and detecting said radiation after passage through said patient's blood;
varying the volume of said patient's blood through gravitational force to change said path length of said tissue probe to provide multiples of said path length;
measuring absorbance of said patient's blood at each multiple of said path length; and
determining the concentration of the blood constituent based on said measured absorbance.

### Claim 2 (depends on 1)

The method of claim 1, wherein said blood constituent comprises hemoglobin.

### Claim 3 (depends on 1)

The method of claim 1, wherein said blood comprises venous blood.

### Claim 4 (depends on 1)

The method of claim 1, wherein said blood comprises arterial blood.

### Claim 5 (depends on 1)

The method of claim 1, further comprising the step of:
verifying said determination of concentration by comparing said radiation path length multiplied by said determined concentration to said measured absorbance.

### Claim 6 (depends on 1)

The method of claim 1, wherein said step of providing tissue probe comprises providing a tissue probe having a first and second radiation emitters, said first radiation emitter being adapted to emit first radiation having a first wavelength, said second radiation emitter being adapted to emit second radiation having a second wavelength, and first and second radiation detectors adapted to receive said first and second radiations, respectively, after absorbance through a radiation path length of said patient's blood and wherein said step of measuring said absorbance comprises measuring said absorbance at said first and second wavelengths.

### Claim 7

A method for noninvasively determining the concentration of a blood constituent comprising the steps of:
providing at least one tissue probe, said tissue probe including a first radiation emitter adapted to emit radiation having a first wavelength and a first radiation detector adapted to receive said radiation after absorbance through a first path length of a patient's blood;
measuring absorbance of said patient's blood by transmitting said radiation at said first wavelength through said patient's blood and detecting said radiation after passage through said patient's blood;
determining absorbance values of said patient's blood at multiples of said path length; and
determining the concentration of the blood constituent based on said absorbance values.

### Claim 8 (depends on 7)

The method of claim 7, wherein said blood constituent comprises hemoglobin.

### Claim 9 (depends on 7)

The method of claim 7, wherein said blood comprises venous blood.

### Claim 10 (depends on 7)

The method of claim 7, wherein said blood comprises arterial blood.