Apparatus and method for measuring blood constituents

• US 4,863,265 A
• Filed: 10/16/1987
• Issued: 09/05/1989
• Est. Priority Date: 10/16/1987
• Status: Expired due to Fees

• Current Assignee: MSA, Mine Safety Appliances Company (MSA Safety, Inc.)
• Original Assignee: Mine Safety Appliances Company (MSA Safety, Inc.)
• Inventors: Olsen, Robert W., Flower, Ronald J., Van Ells, Michael A., Flatau, Ralph
• Primary Examiner(s): Rosenberger, Richard A.
• Application Number:
  US07/109,760
• Time in Patent Office: 690 Days
• Field of Search: 356/41, 356/42, 128/633
• US Class Current: 356/41
• CPC Class Codes: A61B 5/14551 for measuring blood gases
• CPC Class Codes: G01J 2001/4242 Modulated light, e.g. for synchronizing source and detector circuit
• CPC Class Codes: G01J 2001/444 Compensating; Calibrating, e.g. dark current, temperature drift, noise reduction or baseline correction; Adjusting
• CPC Class Codes: G01N 21/3151 using two sources of radiation of different wavelengths G01N21/33 - G01N21/39 take precedence

Abstract

An apparatus for noninvasive determination of constituent concentrations utilizing light wave absorption measurements and methods for processing signals generated by such measurements.

Claims

1. An apparatus for non invasive measurement of blood constituents in a living body comprising:

(a) energy emitting means for emitting electromagnetic energy at a plurality of predetermined wavelengths;

(b) holder means for holding said energy emitting means and directing said electromagnetic energy through an area of living tissue containing flowing blood;

(c) detector means for receiving said electromagnetic energy through said area of living tissue and for producing electrical signals in response to receiving said predetermined wavelengths of electromagnetic energy;

(d) said detector means also receiving ambient electromagnetic energy and producing an electrical signal in response thereto;

(e) signal discriminating means connected to said detector means for separating said electrical signals;

(f) storage means connected to said signal discriminating means for storing said separated signals;

(g) subtraction means connected to said storage means for subtracting said ambient electrical signal from said predetermined wavelength electrical signals to produce data signals;

(h) signal processing means connected to said signal discriminating and signal storage means for amplifying, filtering and conditioning said data signals for further processing;

(i) electrical signal conversion means connected to said signal processing means for converting said data signals to digital data signals;

(j) first control means connected to said energy emitting means and said signal processing means for controlling said energy emissions;

(k) second control means connected to said signal discriminating means and said storage means for controlling said signal separation and storage, to said signal processing means for controlling said signal processing and to said signal conversion means for controlling said signal conversion;

(l) programmable digital arithmetic computation processor means connected to said signal conversion means for receiving said digital data signals and connected to said first and second control means for programmed direction of said control means;

(m) memory means connected to said digital arithmetic processor means for storing program processes;

(n) program processes stored in said memory means for analyzing said digital data signals, for detecting the presence of noise in said signals and for directing said first and second control means whereby said predetermined wavelength electrical signals are produced and received to the exclusion of said ambient electrical signals and said noise;

(o) program processes stored in said memory means for calculating from said predetermined wavelength data signals preselected blood constituent levels; and

(p) display means connected to said processor means for displaying the results of said preselected blood constituent level calculations.

2. The apparatus of claim 1 wherein the presence of noise is detected by deenergizing said energy means, processing the signals received, and directing said display means on the basis of the results to not display data and indicate the presence of excessive noise.

3. The apparatus of claim 1 wherein said processor means directs said control means to produce ambient and predetermined wavelength signals in a plurality of sequences whereby optimum data signals are obtained.

4. An apparatus for non invasive measurement of blood constituents in a living body comprising:

(a) energy emitting means for emitting electromagnetic energy at a plurality of predetermined wavelengths;

(b) holder means for holding said energy emitting means and directing said electromagnetic energy through an area of living tissue containing flowing blood;

(c) detector means for receiving said electromagnetic energy through said area of living tissue and for producing electrical signals in response to receiving said predetermined wavelengths of electromagnetic energy;

(d) said detector means also receiving ambient electromagnetic energy and producing an electrical signal in response thereto;

(e) signal discriminating means connected to said detector means for separating said electrical signals;

(f) signal sampling and storage means connected to said signal discriminating means for sampling and storing said separated signals;

(g) subtraction means connected to said storage means for subtracting said ambient electrical signal from said predetermined wavelength electrical signals to produce data signals;

(h) signal processing means connected to said signal discriminating and signal storage means for amplifying, filtering and conditioning said data signals for further processing;

(i) electrical signal conversion means connected to said signal processing means for converting said data signals to digital data signals;

(j) first control means connected to said energy emitting means and said signal processing means for controlling said energy emissions;

(k) second control means connected to said signal discriminating means and said storage means for controlling said signal separation and storage to said signal processing means for controlling said signal processing and to said signal conversion means for controlling said signal conversion;

(l) programmable digital arithmetic computation processor means connected to said signal conversion means for receiving said digital data signals and connected to said first and second control means for programmed direction of said control means;

(m) memory means connected to said digital arithmetic processor means for storing program processes;

(n) program processes stored in said memory means for analyzing said digital data signals, for detecting the presence of noise in said signals and for directing said first and second control means whereby said predetermined wavelength electrical signals are produced and received to the exclusion of said ambient electrical signals and said noise;

(o) program processes stored in said memory means for calculating from said predetermined wavelength data signals preselected blood constituent levels; and

(p) program processes stored in said memory means for selecting said predetermined wavelength data signals so as to suppress the Traube-Herring effect and calculating said preselected blood constituent levels from said selected signals;

(q) display means connected to said processor means for displaying the results of said preselected blood constituent level calculations.

5. The apparatus of claim 4 wherein said signal sampling storage means have time constants that are longer than the sample period whereby said means provide a high frequency noise filter at a frequency near the sampled data frequency without distorting the desired data.

6. The apparatus of claim 4 wherein said signals are selected by using data at the minimum photoplethysmographic wave point and then at the maximum wave point to calculate a first value of blood constituent level, using data at the next minimum wave point and the preceding maximum wave point to calculate a second value of blood constituent level, repeating said cycle of calculations to provide a final calculated blood constituent level which is averaged to suppress low frequency noise including the Traube-Herring effect.

7. An apparatus for non invasive measurement of blood constituents in a living body comprising:

(a) energy emitting means for emitting electromagnetic energy at a plurality of predetermined wavelengths;

(b) holder means for holding said energy emitting means and directing said electromagnetic energy through an area of living tissue containing flowing blood;

(c) detector means for receiving said electromagnetic energy through said area of living tissue and for producing electrical signals in response to receiving said predetermined wavelengths of electromagnetic energy;

(d) said detector means also receiving ambient electromagnetic energy and producing an electrical signal in response thereto;

(e) signal discriminating means connected to said detector means for separating said electrical signals;

(f) storage means connected to said signal discriminating means for storing said separated signals;

(g) subtraction means connected to said storage means for subtracting said ambient electrical signal from said predetermined wavelength electrical signals to produce data signals;

(h) electrical signal conversion means connected to said signal processing means for converting said data signals to digital data signals;

(i) first control means connected to said energy emitting means and said signal processing means for controlling said energy emissions;

(j) second control means connected to said signal discriminating means and said storage means for controlling said signal separation and storage to said signal processing means for controlling said signal processing and to said signal conversion means for controlling said signal conversion;

(k) programmable digital arithmetic computation processor means connected to said signal conversion means for receiving said digital data signals and connected to said first and second control means for programmed direction of said control means;

(l) memory means connected to said digital arithmetic computation processor means for storing program processes;

(m) program processes stored in said memory means for analyzing said digital data signals, for detecting the presence of noise in said signals and for directing said first and second control means whereby said predetermined wavelength electrical signals are produced and received to the exclusion of said ambient electrical signals and said noise;

(n) program processes stored in said memory means for calculating from said predetermined wavelength data signals preselected blood constituent levels;

(o) adaptive filter means connected with said processor means level for evaluating the results of said preselected blood constituent level calculations with respect to the results of previous calculations and determining a value of the quality of the received signals based on such evaluation; and

(p) display means connected to said processor means for displaying the results of said preselected blood constituent level calculations, and said signal quality value.

8. The apparatus of claim 7 including program processes for calculating from said predetermined wavelength data signals a pulse rate value, further including adaptive filter means connected with said processor means for evaluating the results of said pulse rate calculations with respect to the results of previous calculations, adjusting said value of the quality of the received signals on the basis of that evaluation, and wherein said display means displays the results of said pulse rate calculations and said adjusted signal quality value.