The invention relates to a sensor for measuring a vital parameter in the auditory canal of a human or of an animal and to a method for determining tissue variables, preferably the oxygen saturation in the blood, particularly for performing pulse oximetry, preferably transmission pulse oximetry, in the auditory canal. The sensor comprises a sensor element support (2), which can be positioned at least partially in the auditory canal (8), a sensor element (1), which is connectable to the sensor element support (2) and can be positioned at least partially in the auditory canal (8), and a positioning element (3) suitable for positioning the sensor element support (2) in the auditory canal (8), wherein the positioning element (3) is connectable at least at one end to the sensor element support (2), wherein the position of the sensor element (1) in the auditory canal (8) is determined by the depth of insertion of the sensor element support (2) in the auditory canal (8), and wherein the positioning element (3) has a suitable shape, simulating the anatomy of the inside of the pinna, and is suitable for pressing the sensor element support (2) into the interior of the auditory canal (8) in such a way that the sensor is held stably and a continuous measurement of the vital parameter takes place in the auditory canal (8). A sensor is thus provided that is able to carry out continuous and exact measurement of vital parameters during movement of the body and that at the same time is cosmetically inconspicuous.
