Medical appts. monitoring vital functions of patient - uses piezoelectric film connected to observation device for recording respiratory and cardiac functions together with body movement

摘要

A piezo-electric polyvinylidenfluoride film is used, and under its surface layer is an earthed metal foil layer (12). The top and bottom surfaces (11) of the film are of rubber or plastic sheeting, inside which is a plastic foam layer (13). Inside the foam layer are metal foils, e.g. aluminium chrome foils with a thickness of approximately 30 micrometres, and in the centre is the PVDF plastic film, with a thickness of approximately 40 micrometres. In the appts. is incorporated a band filter for respiration frequencies, and one for ballistocardiography. These filters simultaneously filter out from the signals from the film a frequency band of 0.1-3HZ for passage to a respiratory recording appts. and a frequency band of 10-30 Hz for passage to a ballistocardiographic recording appts. Alarms are a part of the euipment, and function when the frequencies filtered out for respiration and pulse are below predetermined levels.