The invention relates to a needle assembly (1,101,201,301,401,501,601), comprising a hollow needle (3,103,203,303,403,503,603) with a flow channel (3.1,103.1,203.1,303.1,403.1,503.1,603.1) and a needle hub (2,102,202,302,402,502,602). At least one pressure sensitive element (4,104,204,304,404,504,604) is adapted to detect an occlusion in the flow channel (3.1,103.1,203.1,303.1,403.1,503.1,603.1), wherein the pressure sensitive element (4,104,204,304,404,504,604) is modifiable if a pressure in the flow channel (3.1,103.1,203.1,303.1,403.1,503.1,603.1) exceeds a predetermined value.
