Near-infrared noninvasive determination of pH in pulse mode

• US 6,542,762 B1
• Filed: 06/05/2000
• Issued: 04/01/2003
• Est. Priority Date: 07/06/1992
• Status: Expired due to Fees

• Current Assignee: Luminous Medical, Inc.
• Original Assignee: Mark R. Robinson, Mary K. Alam
• Inventors: Robinson, Mark R., Alam, Mary K.
• Primary Examiner(s): Hindenburg, Max F.
• Assistant Examiner(s): KREMER, MATTHEW J
• Application Number:
  US09/587,478
• Time in Patent Office: 1,030 Days
• Field of Search: 600/309-310, 600/322-324, 600/326-327, 600/341-342, 600/336, 356/39-42
• 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 including three or more different wavelengths which exhibit attenuation due to histidine, said wavelengths being in the near infrared range;

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

c) measuring at least a portion of said some 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 related spectral information; and

e) estimating the value of said blood pH from said blood related spectral information.

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

a) a source including at least three different wavelengths of light which exhibit attenuation due to histidine, said wavelengths being in the near infrared range;

b) optics for directing said wavelengths into said tissue;

c) at least one detector for measuring the intensities of at least a portion of said wavelengths emerging from said tissue; and

d) electronics for processing said measured intensities to estimate pH values; and

e) means for indicating said estimated values of pH.

3. A method of determining noninvasively 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 which exhibit attenuation due to histidine, said wavelengths being in the near infrared range;

b) irradiating in vivo and noninvasively said arterial blood with said wavelengths, so that there is attenuation of at least some intensities of said wavelengths, said attenuation being a function of said arterial blood, including histidine in said arterial blood;

c) measuring at least a portion of said some intensities of said wavelengths emerging from said arterial blood 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 intensity attenuation due to histidine;

d) measuring at least a portion of said some intensities of said wavelengths emerging from said arterial blood 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 intensity attenuation due to histidine;

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

f) estimating the value of pH in said arterial blood from said intensity attenuation due to histidine in said measure of change between said diastolic and systolic sets of spectral intensities v. wavelengths.

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

a) irradiating blood containing tissue with wavelengths of light in the near infrared range which are attenuated by histidine, so that there is attenuation of at least some intensities of said wavelengths of said light, said attenuation being a function of said blood containing tissue, including histidine in said blood containing tissue;

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

c) using the presence of blood pulsations in said blood containing tissue and said measured intensities to obtain blood related information; and

d) estimating the value of said blood pH from said blood related information.

5. The method of claim 4, wherein said step of irradiating is performed on pulsatile blood in a human.

6. A quantitative analysis instrument for noninvasive spectroscopic measurement of pH in tissue, said instrument comprising:

a) a source of at least three different wavelengths of light which are attenuated by histidine, said wavelengths being in the near infrared range;

b) optics for directing said wavelengths into said tissue;

c) at least one detector for measuring the intensities of at least a portion of said wavelengths emerging from said tissue;

d) electronics for processing said measured intensities to obtain tissue related information;

e) electronics for processing said tissue related information to estimate pH values; and

f) means for indicating said estimated values of pH.

7. A quantitative analysis instrument for noninvasive spectroscopic measurement of pH in tissue, said instrument comprising:

a) a source of at least three different wavelengths of light which are attenuated by histidine, said wavelengths being in the near infrared range;

b) means for directing said wavelengths into said tissue;

c) at least one means for measuring the intensities of at least a portion of said wavelengths emerging from said tissue;

d) means for processing said measured intensities to obtain tissue related information;

e) means for processing said tissue related information to estimate pH values; and

f) means for indicating said estimated values of pH.

8. A method of determining noninvasively and in vivo, pH in arterial blood utilizing spectra which contains histidine information, said method comprising steps of:

a) irradiating in vivo and noninvasively said arterial blood with wavelengths of light in the near infrared range which exhibit attenuation due to histidine, so that there is attenuation of at least some intensities of said wavelengths of said light;

b) measuring at least a portion of said some intensities of said wavelengths of said light emerging from said arterial blood during a portion of the cardiac cycle of said human to obtain spectral intensities;

c) determining a measure of change in said spectral intensities; and

d) estimating the values of pH in said arterial blood from said measure of change.