part 200 can quickly and easily be attached to the back plate 100 by means of the snap locking without requiring any manual securing measures as schematically shown in fig1 b an opening or a cut out 202 is provided at the central part 205 of the front part 200 for enabling arrangement of a treatment unit 300 of fig5 at the central part 205 of the front part 200 the treatment unit 300 can for example be a unit providing compression and or decompression of the chest or sternum of a patient suffering from a cardiac arrest further the treatment unit 300 can comprise or be realized as a monitoring unit such as an electrocardiograph registering the cardiac activity such a unit can comprise necessary electrodes a control unit and interaction means such as a display unit and or a command unit the treatment unit 300 can further comprise or be realized as a sphygmomanometer arranged to measure the blood pressure the treatment unit can in this case comprise necessary cuffs pressure means a control unit and an interaction means the treatment unit 300 can further comprise or be realized as a means for measuring the oxygen saturation in blood when fastening or securing the legs 210 220 of the front plate 200 to the back plate 100 the shaft like member 130 140 will exert a force on a heel 286 of a claw like member 280 of.