Abstract: An electrode device for transcutaneous PCO.sub.2 measurement with a pH-sensitive measuring electrode behind a CO.sub.2 -permeable membrane, a reference electrode, and an electrical heating device for thermostating the measuring electrode and thermally stimulating the blood flow in the skin in the measuring area, the reference electrode being in direct heat-conductive contact with the electrical heating device and being designed so that it surrounds the measuring electrode. This permits compact design of the electrode in a very small size.

Abstract: The invention relates to an electrochemical measuring device for transcutaneous measurement of arterial partial gas pressure, especially partial pressure of oxygen or carbon dioxide. The measuring device comprises an annular mounting member having a skin contacting surface adapted to be fastened to the skin surface of a patient, and a sensor of the type having a semi-permeable membrane adapted to be releasably connected to the mounting member. In the connected position of the sensor, the membrane is axially spaced from the skin contacting surface of the mounting member so that the membrane, the inner wall of the annular mounting member, and the skin surface define a measuring chamber which may be filled with a gel or another medium, if desired.