A system for monitoring cardiac vibration, respiration, and body movement in bed
Mukai, K.; Yonezawa, Y.; Maki, H.; Ogawa, H.; Ninomiya, I.; Sada, K.; Hamada, S.; Hahn, A.W.
Biomedical Sciences Instrumentation 44: 507-512
2008
ISSN/ISBN: 0067-8856 PMID: 19141966 Document Number: 628102
We have developed a non-invasive system for monitoring cardiac vibrations, respiration and body movement of in-bed hospitalized patients and elderly people who need constant care. These physiological parameters are recorded by 40 kHz ultrasonic transmitter and receiver, which are installed into the bed mattress. The ultrasonic transmitter diffuses an ultrasonic wave into the mattress. The diffusion of the ultrasonic energy is changed by mattress shape variations, which modulate the amplitude of the received ultrasonic signal. The amplitude is also modulated by physiological parameters such as heart pulse, respiration and body movement. The received ultrasonic signal is demodulated by an envelope detection circuit, and the physiological parameters are detected by low, high and band pass filters.