Abstract: The invention relates to a device for detecting physiological measured variables within the body, comprising a catheter which has a tip supporting a sensor and which can be introduced into a blood vessel, the catheter (1) being connected to a transponder unit (2) for wireless transmission of at least one measured variable to an external reading station which is arranged outside the blood vessel (4) after insertion of the catheter (1) into said blood vessel (4), the catheter (1) and the transponder (2) being sealed in a leaktight manner. The invention also relates to a sluice/sleeve for coaxial arrangement on an element for insertion into a blood vessel, in particular a needle and/or a catheter, the sluice/sleeve (6,10,11) being able to be divided at least once in the longitudinal direction.