Apparatus for the electrochemical determination of the partial oxygen pressure in a liquid measuring medium

• US 5,225,063 A
• Filed: 07/10/1991
• Issued: 07/06/1993
• Est. Priority Date: 07/11/1990
• Status: Expired due to Term

• Current Assignee: Sphere Medical Limited (Sphere Medical Holding Ltd.)
• Original Assignee: Siemens AG
• Inventors: Hofmann-Tikkanen, Roland, Gumbrecht, Walter, Preidel, Walter, Schelter, Wolfgang
• Primary Examiner(s): Tung, T.
• Application Number:
  US07/727,981
• Time in Patent Office: 727 Days
• Field of Search: 204/400, 204/412, 204/415, 204/403, 204/402, 204/409, 204/411
• US Class Current: 600/355
• CPC Class Codes: A61B 5/14542 for measuring blood gases A61B5/14551 takes precedence
• CPC Class Codes: A61B 5/1473 invasive, e.g. introduced into the body by a catheter A61B5/1482 takes precedence
• CPC Class Codes: G01N 33/4925 measuring blood gas content, e.g. O2, CO2 , HCO3

Abstract

An apparatus for electrochemically determining the partial oxygen pressure pO₂ in a liquid measuring medium includes a measuring sensor having a working electrode and a counter-electrode. The electrodes are manufactured in thin-film technology and are arranged on a substrate in a measuring channel, to which the measuring medium and a rinse medium can be supplied in alternation. The measuring channel connects a device which controls the flow rate of the measuring medium to a lumen of a double lumen catheter. The rinse medium is suppliable to a second lumen of the double lumen catheter with reversible flow direction. Both lumens have a common orifice which can be introduced into the measuring medium. So-called poisoning of the electrodes in this arrangement is suppressed because the electrodes are flooded in alternation by the measuring medium in a measuring phase and by the rinse medium in a regeneration phase.

Claims

1. An apparatus for electrochemically determining the partial oxygen pressure in a liquid measuring medium comprising:

a measurement cell having a measurement channel;

a multiple lumen catheter having a first lumen in fluid communication at a first end with a source of rinse solution and a second lumen in fluid communication at a first end with said measurement channel, said first and second lumens having common respective orifices at respective second ends adapted for immersion in said fluid medium;

a means for maintaining a constant flow of said fluid medium in said second lumen;

reversible pump means for periodically transferring rinse solution from said source of rinse solution via said first lumen, said common orifices, and said second lumen to said measurement channel so that an alternating sequence of said fluid medium and said rinse solution flows through said measurement channel;

a thin-film microstructure having a working electrode and a counter electrode disposed in a wall of said measuring channel;

means for alternatingly simultaneously covering said working electrode and said counter electrode with said fluid medium during a measuring phase and simultaneously covering said working electrode and said counter electrode with said rinse medium during a regeneration phase; and

measuring circuitry including means for alternatingly electrically connecting said working electrode and said counter electrode to generate a current therebetween in a first direction during said measuring phase for reducing oxygen in said fluid medium and electrically connecting said working electrode and said counter electrode to generate a current therebetween in a second direction during said regeneration phase for desorbing material accumulating on said working electrode, and further including means for measuring said current in said first direction relative to a reference potential during said measuring phase as a measure of said partial oxygen pressure.

2. An apparatus as claimed in claim 1, wherein said microstructure further has a reference electrode also disposed in said wall of said measuring channel, and wherein said means for measuring said current in said first direction is electrically connected to said reference electrode to generate said reference potential at said reference electrode.

3. An apparatus as claimed in claim 2, further comprising a hydrophilic membrane covering said reference electrode, said working electrode, and said counter electrode.

4. An apparatus as claimed in claim 1, further comprising a hydrophilic membrane covering said working electrode and said counter electrode.

5. An apparatus as claimed in claim 1, wherein said working electrode consists of platinum.

6. An apparatus as claimed in claim 1, wherein said working electrode consists of carbon.

7. An apparatus as claimed in claim 1 wherein said means for measuring said current in said first direction is electrically connected to said counter electrode for generating said reference potential at said counter electrode.