A dual lumen CO.sub.2 catheter is formed of medical grade dual lumen silicone rubber tubing which has been impregnated with tridodecyl amine. The silicone tubing is gas permeable, and an external reference electrode is used to monitor the potential across the impregnated outer wall of the dual lumen...http://www.google.fr/patents/US4834101?utm_source=gb-gplus-shareBrevet US4834101 - Catheter-type electrochemical sensors
