US 5,355,880 A · Reliable noninvasive measurement of blood gases

Abstract

Methods and apparatus for, preferably, determining noninvasively and in vivo at least two of the five blood gas parameters (i.e., pH, PCO.sub.2, [HCO.sub.3.sup.- ], PO.sub.2, and O.sub.2 sat.) in a human. The non-invasive method includes the steps of: generating light at three or more different wavelengths in the range of 500 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 at least two of pH, [HCO.sub.3.sup.- ], PCO.sub.2 and a measure of oxygen concentration. The determined values are within the physiological ranges observed in blood containing tissue. The method also includes the steps of providing calibration samples, determining if the spectral intensities v. wavelengths from the tissue represents an outlier, and determining if any of the calibration samples represents an outlier. The determination of the unknown values is performed by at least one multivariate algorithm using two or more variables and at least one calibration model. Preferably, there is a separate calibration for each blood gas parameter being determined. The method can be utilized in a pulse mode and can also be used invasively. The apparatus includes a tissue positioning device, a source, at least one detector, electronics, a microprocessor, memory, and apparatus for indicating the determined values.

Claims62

Dependent claims

A method of determining non-invasively and in vivo at least two blood gas parameters in a human, said method comprising steps of:

a. generating light at three or more different wavelengths, said wavelengths being in the range of 500 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 and the direct and indirect spectral influences resulting from the unknown values of pH, HCO.sub.3.sup.-, PCO.sub.2, PO.sub.2 and O.sub.2 saturation in said blood containing tissue;
c. measuring said intensities of said wavelengths emerging from said blood containing tissue to obtain a set of at least three spectral intensities v. wavelengths;
and
d. determining said unknown values of at least two of pH, HCO.sub.3.sup.-, PCO.sub.2, and a measure of oxygen concentration in said blood containing tissue from said intensities emerging from said blood containing tissue, said values being within the physiological ranges observed in blood containing tissue.

2 more elements

A method of determining invasively and in vivo at least two blood gas parameters in human blood, said method comprising steps of:

a. generating light at three or more different wavelengths, said wavelengths being in the visible and infrared region;
b. irradiating blood 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 the direct and indirect influences resulting from the unknown values of pH, HCO.sub.3.sup.-, PCO.sub.2, PO.sub.2 and O.sub.2 sat. in said blood;
c. measuring said intensities of said wavelengths from said blood to obtain a set of at least three spectral intensities v. wavelengths;
and
d. determining said values of at least two of pH, HCO.sub.3.sup.-, PCO.sub.2, and a measure of oxygen concentration in said blood from said intensities emerging from said blood, said values being within the ranges observed in blood.

2 more elements

A method of determining non-invasively and in vivo two or more blood gas parameters in arterial blood in a human, said method comprising steps of:

a. generating light at three or more different wavelengths, said wavelengths being in the range of 500 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 and the direct and indirect spectral influences resulting from the unknown values of pH, HCO.sub.3.sup.-, PCO.sub.2, PO.sub.2 and O.sub.2 sat. in said arterial blood;
c. measuring 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;
d. measuring 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;
e. determining the measure of change between said diastolic and systolic sets of spectral intensities v. wavelengths;
and
f. determining said unknown values of at least two of pH, HCO.sub.3.sup.-, PCO.sub.2, and a measure of oxygen concentration in said arterial blood from 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 more elements

A quantitative analysis instrument for noninvasive measurement of two or more blood gas parameters present in blood containing tissue of a human, said instrument comprising:

a. a device for positioning said blood containing tissue;
b. a source of at least three different wavelengths of light positioned relative to said tissue positioning device, to direct light into said blood containing tissue, said wavelengths being in the range of 500 to 2500 nm;
c. at least one detector positioned relative to said tissue positioning device for measuring the spectral intensities of at least three wavelengths of said light emerging from said blood containing tissue during the diastolic portion of the cardiac cycle of said human, to obtain a diastolic set of spectral intensities v. wavelengths, and for measuring the spectral intensities of at least three wavelengths of said light emerging from said blood containing tissue during the systolic portion of the cardiac cycle of said human, to obtain a systolic set of spectral intensities v. wavelengths;
d. memory means for storing said diastolic set of spectral intensities v. wavelengths and said systolic set of spectral intensities v. wavelengths;
e. electronics, a microprocessor and said memory means for processing said diastolic and systolic sets of spectral intensities to determine a measure of change between said diastolic and systolic sets, to obtain a blood specific set of spectral intensities v. wavelengths, said memory means including a multivariate algorithm and a multivariate calibration model, said electronics, said microprocessor and said memory means processing said blood specific set of spectral intensities v. wavelengths to determine at least two of pH, PCO.sub.2, HCO.sub.3.sup.-, and a measure of oxygen saturation at values within the physiological ranges observed in said blood, said algorithm using at least two variables, said model being a function of conventionally measured blood gas parameters obtained from calibration samples and a set of spectral intensities v. wavelengths obtained from irradiating said calibration samples with at least three wavelengths of light in the range of 500-2500 nm;
and
f. means for indicating said determined values of said blood gas parameters.

4 more elements

Dependencies are inferred from the claim text.

Reliable noninvasive measurement of blood gases

Life of this patent

Reliable noninvasive measurement of blood gases

Life of this patent

Abstract

Claims62