The invention relates to medical devices and is designed to automatically identify the epidural space in the implementation of epidural anesthesia. The technical problem to be solved by the claimed utility model, is to provide a reliable determination of the epidural space during epidural anesthesia. An apparatus for detecting the epidural space of the first embodiment comprises a delivery fluid comprising a housing with inlet and outlet openings provided with abutments with the inlet port, the plunger comprising a head and a stem, the plunger is provided fixed on a head seal and placed in the cavity the housing so that between its head and the housing wall a chamber for a fluid displacement unit disposed in the liquid delivery unit and is designed to maintain a constant force displacement fluid contained in the fluid delivery unit, a tubular needle device coupled to the fluid delivery unit. The apparatus according to the second embodiment differs from the first embodiment in that the plunger rod includes an elongate cavity that has an opening at the rear (aft) of the stem and comprises a needle unit. The apparatus according to the third embodiment differs from the device of the first embodiment in that the plunger has a second delivery channel the liquid which passes from the head to the rear end of the rod and allows delivering additional agent (e.g., an anesthetic for epidural anesthesia) into the patients body, in addition to the liquid in chamber used for the detection of the epidural space. The valve in the tail portion of the channel provides a one-way delivery of substances through the delivery channel to the outlet opening of the housing and prevents reflux of the substance. The apparatus according to the fourth embodiment differs from the device of the first embodiment in that instead of sealing plunger comprises a container of variable volume, which is located in front of the head-piston rod in the body cavity and can also be connected to the outlet of th
