A dilator assembly (1) serves for percutaneous dilatational tracheostomy. The dilator assembly comprises a dilator element (2) having a wall (11) and a proximal end part (5) extending into a distal tip part (6) via an intermediate part (7). At least the wall (11) of the proximal end part (5) of the dilator element (2) has a U-shaped cross section defining a dilator opening (20) along at least the length of the proximal end part (5). The dilator assembly may taper towards the distal tip part. The dilator assembly is used in a device for facilitating tracheostomy. The device has a first branch (52) for arranging inside the trachea (74), and a second branch (53) for creating a tracheostoma (84). The first branch (52) has a first end (54) to be introduced into the trachea (74), which first end (54) has a receiving means (55), and an opposing second end (56) provided with a first coupling part (57). The second branch (53) has a first end (58) with a guide means (59) for a neck penetration means (60) and an opposing second end (61) with a second coupling part (62) for detachably coupling with the first coupling part (57) of the first branch (52).
