An endo-tracheal catheter for use in an anesthetic procedure comprises a catheter tube to be inserted into the trachea of a patient, the catheter tube having a tubular wall defining an inner lumen for guiding a gaseous flow, and a connection piece which defines a chamber in fluid connection with the catheter tube and comprising a port for connecting a detection device to the endo-tracheal catheter for detecting at least one substance in the gaseous flow flowing through the catheter tube. An insert tube is received in the inner lumen of the catheter tube for guiding the gaseous flow through the catheter tube and/or a coating covers the tubular wall at a side facing the inner lumen for guiding the gaseous flow through the catheter tube.