Combined sensor for the transcutaneous measurement of oxygen and carbon dioxide in the blood

• US 4,840,179 A
• Filed: 11/17/1987
• Issued: 06/20/1989
• Est. Priority Date: 11/17/1986
• Status: Expired due to Fees

• Current Assignee: PPG Hellige GmbH
• Original Assignee: Hellige GmbH
• Inventors: Ullrich, Georg J.
• Primary Examiner(s): Cohen, Lee S.
• Application Number:
  US07/121,713
• Time in Patent Office: 581 Days
• Field of Search: 128/633, 128/635, 128/664-667
• US Class Current: 600/326
• CPC Class Codes: A61B 5/14539 for measuring pH
• CPC Class Codes: A61B 5/14542 for measuring blood gases A61B5/14551 takes precedence
• CPC Class Codes: A61B 5/14552 Details of sensors specially adapted therefor
• CPC Class Codes: A61B 5/1477 non-invasive

Abstract

The combined sensor with a thermostatted heating device (7, 23) for the simultaneous and continuous transcutaneous measurement of oxygen (O₂) and of carbon dioxide (CO₂) in the blood contains a measuring device (1) for the partial pressure of CO₂ (pCO₂), in which there is pure optical/spectrometric operation or which operates on the principle of pH measurement in an electrolyte (8), and which is separated from the measuring site on the skin by a membrane (13) which is permeable to both CO₂ and light, and contains another measuring device (24, 25, 26) for the spectrometric measurement of the blood oxygen saturation (sO₂). The advantage over a known pO₂ /pCO₂ combined sensor is that the combined sensor according to the invention can be operated at a low operating temperature of, for example, 42° C. or less, so that continuous measurement for 24 hours, for example, is possible without resiting or recalibrating the sensor, and thus it is simple to use in the domestic milieu.

Claims

1. A sensor element for simultaneous, continuous, transcutaneous measurement of the partial pressure of carbon dioxide and of the oxygen saturation in the blood of a living body, said sensor element comprising:

a housing having a planar measuring surface;

a membrane, permeable to carbon dioxide, sealably disposed about the measuring surface, said membrane having inner and outer surfaces;

a reference electrode and a measuring electrode embedded in the measuring surface and electrically insulated each from the other;

two light emitting diodes embedded in the measuring surface each emitting light of different wave length and so positioned that the emitted light beams do not mutually interfere;

photoelectric receptor means embedded in the measuring surface; and

a thin layer of electrolyte disposed between the measuring surface and the inner surface of the membrane;

whereby when the outer surface of the membrane is brought in contact with the skin, carbon dioxide diffuses through the membrane changing the pH of the electrolyte solution which change in pH is sensed by the reference electrode and the measuring electrode which change in pH is related to the partial pressure of carbon dioxide and whereby the light emitted from the diodes after diffusion through the skin is detected by the photoelectric receptor means and the oxygen saturation of the blood is determined by the principle of pulse oximetry.

2. The sensor element of claim 1 wherein said housing has a heating coil embedded therein.

3. The sensor element of claim 1 wherein the reference electrode is a silver/silver chloride electrode and the measuring electrode is an iridium/iridium oxide electrode.

4. The sensor element of claim 1 wherein one of the diodes emits light at a wavelength in the infrared region of the electromagnetic spectrum and the other diode emits light at a wavelength in the red region of the electromagnetic spectrum.

5. The sensor element of claim 4 wherein the infrared wavelength is 805 nanometers and the red wavelength is 650 nanometers.