Devices and procedures for in vitro calibration of pulse oximetry monitors

• US 4,834,532 A
• Filed: 12/05/1986
• Issued: 05/30/1989
• Est. Priority Date: 12/05/1986
• Status: Expired due to Fees

• Current Assignee: Oregon State University (Oregon University System)
• Original Assignee: Oregon State University (Oregon University System)
• Inventors: Yount, John E.
• Primary Examiner(s): MIS, DAVID C
• Application Number:
  US06/938,275
• Time in Patent Office: 907 Days
• Field of Search: 356/39, 356/40, 356/41, 356/42, 356/243, 250/252.1, 128/632, 128/633
• US Class Current: 356/41
• CPC Class Codes: A61B 2560/0233 Optical standards
• CPC Class Codes: A61B 5/1495 Calibrating or testing of in-vivo probes
• CPC Class Codes: G01N 2021/3144 for oxymetry
• CPC Class Codes: G01N 21/274 Calibration, base line adjustment, drift correction
• CPC Class Codes: G01N 2201/127 Calibration; base line adjustment; drift compensation

Abstract

A device and method for calibration of pulse oximeters is disclosed. A standard specimen that has optical charactertistics of hemoglobin of a known oxygen saturation is placed in the light path of a pulse oximeter probe. The image of a pulse is also created by providing a filter that periodically increases and decreases the amount of light allowed to reach the sensor of the probe. In one embodiment, the filter can comprise a pair of polarizing filters rotated with respect to one another. In another embodiment, a wedge of a filtering medium, such as oxygenated blood, is reciprocated in the light path, the wide portions of the wedge attenuating a greater amount of light than the narrow portions.

Claims

1. A device for testing the accuracy of a pulse oximeter which comprises a light source and a light detector in opposing relationship to one another such that said source directs a beam of light toward said detector, said device comprising:

pulse means for creating an image of a pulse by varying the intensity of light received by said light detector and for providing a sample of material which simulates hemoglobin of known oxygen saturation between said source and detector as said pulse means creates said image;

said pulse means comprising a polarization filter which periodically increases and decreases the amount of light which passes from said light source to said light detector.

2. A device for testing the accuracy of a pulse oximeter which comprises a light source and a light detector in opposing relationship to one another such that said source directs a beam of light toward said detector, said device comprising:

pulse means for creating an image of a pulse by varying the intensity of light received by said light detector and for providing a sample of material which simulates hemoglobin of a known oxygen saturation between said source and detector as said pulse means creates said image;

said pulse means comprising a member which is reciprocated back and forth along a path of movement between said light source and light detector, said member having progressively changing light transmissivity along said path of movement.

3. A device for testing the accuracy of a pulse oximeter which comprises a light source and a light detector in opposing relationship to one another such that said source directs a beam of light toward said detector, said device comprising:

pulse means for creating an image of a pulse by varying the intensity of light received by said light detector and for providing a sample of material which simulates hemoglobin of a known oxygen saturation between said source and detector as said pulse means creates said image;

said pulse means comprising a member which is reciprocated back and forth along a path of movement between said light source and light detector, said member being a cuvette defining a wedge-shaped chamber filled with a medium that has optical characteristics of hemoglobin of a known oxygen saturation so that the cuvette has a progressively changing light transmissivity along said path of movement.

4. A device for testing the accuracy of a pulse oximeter which comprises a light source and a light detector in opposing relationship to one another such that said source directs a beam of light toward said detector, said device comprising:

pulse means for simulating an image of a cardiovascular pulsation by gradually varying the intensity of light received by said light detector;

said pulse means comprising a body of a light-absorbing medium which simulates hemoglobin of a known oxygen saturation, which body is moved along a path of movement between said light source and light detector, said body varying in thickness to be progressively changing in light transmissivity along said path of movement such that as said body is moved, said image of cardiovascular pulsation is simulated.

5. A method for testing the accuracy of a pulse oximeter wherein said pulse oximeter comprises a light source and light detector in opposing relationship to one another such that said light source directs a beam of light toward said detector, said method comprising:

actuating said light source to shine light toward said detector; and

creating an image of a pulse by placing a pair of parallel polarizing plates between said source and detector and then rotating one of said plates in a manner suitable to produce a variation of light intensity received by said source which mimics the variation of light intensity produced by a pulse and by providing a sample of material that simulates hemoglobin of a known oxygen saturation between said source and detector as said light intensity is being varied.

6. A method for testing the accuracy of a pulse oximeter wherein said pulse oximeter comprises a light source and light detector in opposing relationship to one another such that said light source directs a beam of light toward said detector, said method comprising:

actuating said light source to shine light toward said detector; and

creating an image of a pulse by providing a wedge of a light-absorbing medium, which wedge increases in thickness along a path of reciprocation, then reciprocating said wedge along said path between said source and detector.

7. The method of claim 6 wherein said wedge contains hemoglobin of a known oxygen saturation.

8. A cuvette suitable for use in testing the accuracy of a pulse oximeter, the cuvette defining a wedge-shaped chamber filled with a medium that has optical characteristics of hemoglobin of a known oxygen saturation.