Development of a PVDF Piezopolymer Sensor for Unconstrained In-Sleep Cardiorespiratory Monitoring

This paper reports the development of an unconstrained sensing technique for monitoring the respiration and heartbeats during sleep using a polyvinylidene fluoride (PVDF) piezopolymer film sensor with the aim that the sensor can be used on the ordinary bed together with the condition that the use of the sensor does not interfere the daily sleep of the patient under measurement. A PVDF film is used as the sensory material in the sensor system. The film is placed under the sheet at the location of the thorax to pick up the fluctuation of the pressure on the bed caused by the respiratory movement and heartbeats. Wavelet multiresolution decomposition analysis is used for the detection of respiration and heartbeat from the sensor output. It is shown that the respiration and heartbeats can simultaneously be detected by the sensor with the use of the wavelet multiresolution decomposition analysis.