OXIMETER FOR MONITORING OXYGEN SATURATION IN BLOOD

• US 3,799,672 A
• Filed: 09/15/1972
• Issued: 03/26/1974
• Est. Priority Date: 09/15/1972
• Status: Expired due to Term

• Current Assignee: Gerald G. Vurek
• Original Assignee: Gerald G. Vurek
• Inventors: Vurek, Gerald G.
• Primary Examiner(s): Corbin, John K.
• Assistant Examiner(s): McGraw, V. P.
• Application Number:
  US05/289,287
• Time in Patent Office: 557 Days
• Field of Search: 356/39,41,87,88,93,95,97 250/218
• US Class Current: 356/41
• CPC Class Codes: G01N 21/3151 using two sources of radiation of different wavelengths G01N21/33 - G01N21/39 take precedence

Abstract

A device for monitoring blood oxygen saturation during extracorporeal bypass procedures comprises a dual wavelength oximeter utilizing an infrared (905 nm) light-emitting diode and a visible red (655nm) light emitting diode to alternately illuminate blood as it flows through a plastic cuvet. The ratio of the infrared signal to the red signal received by a phototransistor is computed by a simple electro-optical feedback circuit, the ratio being linearly related to blood oxygen saturation over the range extending from 100 percent to below 40 percent.

Claims

1. An oximeter for measuring oxygen content in the blood comprising:

a first controllable source of light;

a second controllable source of light;

light sensitive means located so as to be illuminated by the first and second source of light;

means for placing a blood sample in the optical paths between the two light sources and the light sensitive means so that light from said sources illuminates the blood;

means for alternately energizing the light sources such that the output of the second source of light is controlled by and proportional to the optical signal of the first source of light; and

means for determining the ratio of the signals received by the light sensitive means from the two light sources.

2. The oximeter of claim 1 wherein the output light from each light source is directly and linearly related to its input current.

3. The oximeter of claim 2 wherein the first and second light sources operate at different wavelengths.

4. The oximeter of claim 3 wherein the first light source has a wavelength of about 655 nm.

5. The oximeter of claim 4 wherein the second light source has a wavelength of about 905 nm.

6. The oximeter of claim 5 wherein the light sensitive means is a phototransistor.

7. The oximeter of claim 6 wherein the means for holding the blood sample is a U-shaped slot with light channels in the bottom of the slot.

8. The oximeter of claim 7 wherein the means for alternately energizing the light sources comprises electronic switches.

9. The oximeter of claim 8 wherein the means for determining the ratio between the two optical sigNals is a high gain difference amplifier.

10. An oximeter for measuring oxygen saturation of the blood comprising two light sources operating at different wavelengths and having their output light directly and linearly related to their input currents;

a common light detector to receive light from both sources;

means for placing the blood to be measured in the optical paths of both light sources so that the blood is illuminated by the light sources and the scattered light from the blood falls on the light detector;

a high gain difference amplifier connected to the output of the detector;

switching means for alternately energizing the light sources;

a voltage to current converter connected to the output of the difference amplifier;

voltage storage means connected to the output of the difference amplifier to store the output signal from the detector when the first light source is energized;

means for applying the voltage on the storage means to the input of the difference amplifier; and

means for applying the output of the converter to the second light source whereby the output of this second light source is proportional to the output from the converter and therefore the optical signal from the first light source.