The invention relates to a device and a method for stopping bleeding at the puncture sites of vessels of patients undergoing an extracorporeal treatment, in particular dialysis. The device has a controller which controls the introduction of fluid into an expandable chamber arranged on a strip-shaped basic element and/or draining from the chamber. The invention also relates to an evaluation unit having at least one sensor for measuring the degree of filling of the chamber. Furthermore, the invention relates to a medical technical treatment unit as an arrangement of a hemodialysis machine and the device.
