A catheter structure equipped with an adjustable self-locating device comprises a flexible tube (16,116,216) which has one end (18,118,218) intended to be introduced into the cavity to be evacuated and provided with a hole (20,120,220). A duct (28,43,128,228) associated with the flexible tube (16,116,216) connects a diametral chamber (22,122,222) to means for supplying and controlled discharging of a pressurised fluid. The diametral chamber (22,122,222) consists of a circular rim portion concentric with the flexible tube (16,116,216) and defined by a membrane (24,124,224) which forms a single surface zone (30,130,230) of said flexible tube without diametral chamber (22,122,222), in which said hole (20,120,220) is formed.
