The invention relates to a medico-technical device for at least partially introducing into a body passage. Said device comprises an elongate, tubular, flexible internal body (2), an elongate exterior enveloping body (3) which surrounds, at least partially, said internal body (2) on the periphery thereof, and a device (4) for transferring the device (1) from a flexible state to a rigid state and vice-versa. The invention is characterized in that the internal body (2), which is in the form of a double tube (5), comprises an inner tube (6) which forms an inner wall (8) of the internal body (2) and an external tube (7) which forms an external wall (9) of the internal body (2), said external tube (7) surrounding the inner tube (6) in a concentric manner on the periphery thereof. The invention is characterized in that the device (4) for transferring the device (1) from a flexible state into a rigid state and vice-versa is embodied in such a manner that the external tube (7) lengthens in a radial manner by increasing the pressure in an annular shaped intermediate chamber (10) and exerts pressure on the enveloping body (3).
