An endo-tracheal catheter (1) for use in an anesthetic procedure comprises a catheter tube (10) to be inserted into the trachea (40) of a patient (4), the catheter tube (10) having a tubular wall (101) defining an inner lumen (102) for guiding a gaseous flow, and a connection piece (11) which defines a chamber (110) being in fluid connection with the catheter tube (10) and comprising a port (110) for connecting a detection device (2) to the endo-tracheal catheter (1) for detecting at least one substance in the gaseous flow flowing through the catheter tube (10). Herein, an insert tube (13) is received in the inner lumen (102) of the catheter tube (10) for guiding the gaseous flow through the catheter tube (10) and/or a coating (103) covers the tubular wall (101) at a side facing the inner lumen (102) for guiding the gaseous flow through the catheter tube (10). In this way, an endo-tracheal catheter is provided which allows for an accurate measurement of a substance concentration in a gaseous flow, in particular in the context of an anesthesia procedure.
