Near-infrared noninvasive determination of pH in pulse mode

• US 6,073,037 A
• Filed: 08/10/1998
• Issued: 06/06/2000
• Est. Priority Date: 07/06/1992
• Status: Expired due to Term

• Current Assignee: Luminous Medical, Inc., Sandia Corporation (Martin Marietta Corporation), Rio Grande Medical Technologies Incorporated
• Original Assignee: Sandia Corporation (Martin Marietta Corporation), Rio Grande Medical Technologies Incorporated
• Inventors: Alam, Mary K., Robinson, Mark R.
• Primary Examiner(s): Dvorak, Linda C. M.
• Assistant Examiner(s): YARNELL, BRYAN KEITH
• Application Number:
  US09/131,944
• Time in Patent Office: 666 Days
• Field of Search: 600/310, 600/322, 600/323, 600/326, 600/327, 600/341, 600/342, 356/39-41
• US Class Current: 600/310
• CPC Class Codes: A61B 5/02007 Evaluating blood vessel condition, e.g. elasticity, compliance
• CPC Class Codes: A61B 5/14539 for measuring pH
• CPC Class Codes: A61B 5/14546 for measuring analytes not otherwise provided for, e.g. ions, cytochromes
• CPC Class Codes: A61B 5/1455 using optical sensors, e.g. spectral photometrical oximeters
• CPC Class Codes: A61B 5/352 Detecting R peaks, e.g. for synchronising diagnostic apparatus; Estimating R-R interval
• CPC Class Codes: A61B 5/6826 Finger
• CPC Class Codes: A61B 5/6838 Clamps or clips

Abstract

Methods and apparatus for, preferably, determining noninvasively and in vivo pH in a human. The non-invasive method includes the steps of: generating light at three or more different wavelengths in the range of 1000 nm to 2500 nm; irradiating blood containing tissue; measuring the intensities of the wavelengths emerging from the blood containing tissue to obtain a set of at least three spectral intensities v. wavelengths; and determining the unknown values of pH. The determination of pH is made by using measured intensities at wavelengths that exhibit change in absorbance due to histidine titration. Histidine absorbance changes are due to titration by hydrogen ions. The determination of the unknown pH values is performed by at least one multivariate algorithm using two or more variables and at least one calibration model. The determined pH values are within the physiological ranges observed in blood containing tissue. The apparatus includes a tissue positioning device, a source, at least one detector, electronics, a microprocessor, memory, and apparatus for indicating the determined values.

Claims

1. A method of determining pH in pulsatile blood in a human utilizing spectra which contains histidine information, said method comprising steps of:

a) generating light at three or more different wavelengths, said wavelengths being in the range of 1000 nm to 2500 nm;

b) irradiating blood containing tissue with said wavelengths so that there is differential attenuation of at least some intensities of said wavelengths, said wavelength dependent differential attenuation being a function of said blood containing tissue, including histidine in said blood containing tissue;

c) measuring at least a portion of said intensities of said wavelengths emerging from said blood containing tissue;

d) using the presence of blood pulsations in said blood containing tissue and said measured intensities to obtain blood specific spectral information; and

e) estimating said value of said blood pH from said blood specific spectral information by utilizing wavelength dependent differential attenuation derived from said histidine.

2. A quantitative analysis instrument for noninvasive spectroscopic measurement of pH in pulsatile blood in human tissue, said instrument comprising:

a) a source of at least three different wavelengths of light, said wavelengths being in the range of 1000 nm to 2500 nm, at least some of the said wavelengths having a wavelength dependent differential attenuation due to histidine;

b) optics for directing said wavelengths into said blood containing tissue;

at least one detector for measuring the intensity of at least a portion of said wavelengths emerging from said blood containing tissue;

c) electronics for processing said measured intensities to obtain blood specific spectral information; and

d) electronics for processing said blood specific spectral information containing wavelengths that are differentially attenuated by histidine to estimate pH values in said blood; and

e) means for indicating said estimated values of blood pH.

3. A method of determining non-invasively and in vivo, pH in arterial blood in a human utilizing spectra which contains histidine information, said method comprising steps of:

a) generating light at three or more different wavelengths, said wavelengths being in the range of 1000 nm to 2500 nm;

b) irradiating in vivo and non-invasively blood containing tissue with said wavelengths, so that there is differential attenuation of at least some intensities of said wavelengths, said wavelength dependent differential attenuation being a function of said blood containing tissue. including histidine in said arterial blood;

c) measuring at least a portion of said intensities of said wavelengths emerging from said blood containing tissue during the diastolic portion of the cardiac cycle of said human to obtain a diastolic set of at least three spectral intensities v wavelengths, some of said wavelengths having some attentuation due to histidine;

d) measuring at least a portion of said intensities of said wavelengths emerging from said blood containing tissue during the systolic portion of said cardiac cycle to obtain a systolic set of at least three spectral intensities v. wavelengths, some of said wavelengths having some attentuation dule to histidine;

e) determining the measure of change between said diastolic and systolic sets of spectral intensities v. wavelengths; and

f) estimating the values of pH in said arterial blood from said wavelength depedent attenuation due to histidine included in said measure of change between said diastolic and systolic sets of spectral intensities v. wavelengths, said values being within the ranges observed in arterial blood.

4. The method as set forth in claim 3, further including the step of determining whether said set of spectral intensities v. wavelengths from said blood containing tissue represents an outliner by comparing said set of spectral intensities v. wavelengths from said blood containing tissue with a set of spectral intensities v. wavelengths obtained from radiating calibration samples.

5. The method as set forth in claim 4, wherein said determination of whether said set of spectral intensities v. wavelengths from said blood containing tissue represents an outliner includes the step of comparing said set of spectral intensities v. wavelengths from said blood containing tissue to said set of spectral intensities v. wavelengths from said calibration samples, to determine a measure of the magnitude of the difference between said set of spectral intensities v. wavelengths from said blood containing tissue and said set of intensities v. wavelengths from said calibration samples.