A device for the determination of at least one compression parameter during the administration of cardiopulmonary resuscitation (CPR) on a patient. The device includes a compression unit adapted to move in accordance with the chest of a patient and a surface unit adapted to move in accordance with a surface supporting the patient. The compression unit has one of a signal component and reference component, the surface unit has the other of the signal component and the reference component. The device also includes a processor configured to determine a relative measurement between the compression unit and the surface unit using data derived from the signal component and the reference component. The processor is further configured to determine the at least one compression parameter based on the relative measurement. The determined at least one compression parameter takes into account any motion and/or displacement of the surface.