An EMFi-film sensor based ballistocardiographic chair: performance and cycle extraction method

Abstract

New sensor technologies open possibilities for measuring traditional biosignals in new innovative ways. This, together with the development of signal processing systems and their computing power, can sometimes give new life to old measurement techniques. Ballistocardiogram is one such technique, originally promising but quickly replaced by the now very popular electrocardiogram. A ballistocardiograph chair, designed to look like a normal office chair, was built and fitted with pressure sensitive EMFi-films. The films are connected via a charge amplifier to a medical bioamplifier. The system was accepted for medical use in Tampere University Hospital and patient measurements have been performed. The system is presented and it's performance evaluated. A wireless version of the system is needed to hide the cabling from the user. This will make the chair indistinguishable from a normal office chair. Overview of first wireless prototype is given. To analyze recorded BCG, individual BCG cycles must be extracted from the signal containing respiration and movement artifacts. A method for this and results of it's application are presented. The developed system can be used for BCG measurements and it is able to automatically extract individual BCG cycles, but it has some limitations which are presented in the paper.

Film-type transducer materials PVDF and EMFi in the measurement of heart and respiration rates

“…However, here the measurement is based on ballistocardiography (BCG). BCG is generated by the movement of heart and blood [8]. The movement can be measured with force or acceleration sensors [14].…”

“…The movement can be measured with force or acceleration sensors [14]. Most relevant components of BCG signal exist within frequencies from 1 to 20 Hz [8]. If only the heart rate is measured, the suitable frequency range is from 0.83 Hz to 3.33 Hz corresponding to the heart rates 50 and 200 beats per minute.…”

“…The sensor was attached to a wheel to monitor the physiological state of a driver [6]. Koivistoinen et al developed a system for measuring ballistocardiogram (BCG) in a sitting position in a normal chair with EMFi sensors [7], [8], [9]. Similar measurements are done by Postolache et al [10] and Kim et al [11].…”

Recognition of aging effect from cardiomechanical signals using novel SF-ART neural network

“…Another technique applies a rigid piezoelectric force transducer resting on steel chair to gather the subject's resting body movement including the BCG signal. The same chair structure has been explored for measurement of BCG using EMFi-film sensors [9].…”

Cardiac induced localised motion of the human torso detected by a long period grating fibre optic sensing scheme

“…These forces occur on the sudden ejection of blood into the great vessels with each heartbeat. The predominant frequency range associated with this technique is 1 to 40Hz and detection can be made non-invasively at the chest surface 11,12 . It is also known that the sounds or mechanical motions of a single cardiac cycle of a human heart can be divided into two dominant events 13 .…”