Pulse oximeter with probe difference compensation

• US 5,267,562 A
• Filed: 08/07/1992
• Issued: 12/07/1993
• Est. Priority Date: 05/28/1992
• Status: Expired due to Fees

• Current Assignee: Nihon Kohden Corporation
• Original Assignee: Nihon Kohden Corporation
• Inventors: Ozawa, Hideo, Takeda, Sunao, Ukawa, Teiji
• Primary Examiner(s): Cohen, Lee S.
• Assistant Examiner(s): PONTIUS, KEVIN LANE
• Application Number:
  US07/925,636
• Time in Patent Office: 487 Days
• Field of Search: 128/633, 356/41
• US Class Current: 600/323
• CPC Class Codes: A61B 2562/085 combined with means for recording calibration data
• CPC Class Codes: A61B 5/14551 for measuring blood gases

Abstract

A pulse oximeter of the present invention is to provide a greatly simplified in construction and a simplified procedure for performing arithmetic operations. The pulse oximeter of the present invention comprises a light-emitting diode which is provided in a probe and that illuminates a living tissue with red light of a reference wavelength, a light-emitting diode that illuminates the living tissue with infrared light, a light-receiving device that detects the optical output that remains after the living tissue absorbs the two wavelengths of red light and infrared light that have been issued from the light-emitting diodes, detectors which, on the basis of the detection output of the light-receiving device, compute the pulsating components of absorbances for the two wavelengths, a multiplier that multiplies the value from the detector by an appropriate coefficient in order to adjust that the value detected when using red light of a wavelength offset from the reference wavelength is gain-adjusted for correction to a known value obtained when using red light of the reference wavelength, a computing means that computes an absorbance ratio using both the value after gain adjustment that is delivered from the multiplier and the value from the detector, and a computing means that computes the oxygen saturation of arterial blood using the computed value. Information on the coefficient is provided by resistor which is built in the probe.

Claims

1. A pulse oximeter comprising:

a probe adapted to be attached to an organism, said probe including;

a first light source for illuminating a living tissue of said organism including an arterial blood stream with a first light of a first predetermined wavelength;

a second light source for illuminating said living tissue of said organism including said arterial blood stream with a second light of a second predetermined wavelength; and

light receiving means for detecting optical outputs of said first and second lights which pass through and are not absorbed by said tissue of said organism;

first computing means, responsive to detection outputs of said light receiving means, for computing pulsating components of absorbance of said first light and said second light due to said arterial blood stream based on said detection outputs of said light receiving means;

gain adjusting means for multiplying a first output of said first computing means by a coefficient to compensate for differences between the first predetermined wavelength of said first light and a predetermined reference wavelength so as to produce a gain-adjusted value;

second computing means, responsive to a second output of said first computing means and said gain-adjusted value, for computing an absorbance ratio based on said second output of said first computing means and said gain-adjusted value; and

third computing means for computing an oxygen saturation of arterial blood on a basis of said absorbance ratio delivered from said second computing means.

2. A pulse oximeter as claimed in claim 1, wherein said gain adjusting means comprises:

a resistor disposed in said probe having a value of resistance corresponding to said coefficient; and

a multiplier coupled to said resistor for multiplying said first output of said first computing means by said coefficient.

3. A pulse oximeter as claimed in claim 1, wherein said first light source is a red light source.

4. A pulse oximeter as claimed in claim 1, wherein said predetermined reference wavelength is substantially 660 nm.

5. A pulse oximeter as claimed in claim 1, wherein said second light source is an infrared source.