Session SB2.5

Measurement of Heart Rate and Respiratory Rate Using a Textile-Based Wearable Device in Heart Failure Patients

F Chiarugi*, I Karatzanis, G Zacharioudakis, P Meriggi, F Rizzo, M Stratakis,
S Louloudakis, C Biniaris, M Valentini, M Di Rienzo, G Parati

FORTH - Institute of Computer Science
Heraklion, Greece

Changes in heart rate (HR) and respiratory rate (RespR) may be used as markers of early decompensation in chronic heart failure (CHF) patients monitored at home. Aimed at improving quality of care and at reducing hospitalization rate and health care costs in CHF, progress in technology has led to the development of small portable and even wearable devices for the acquisition and transmission of vital signs of interest to a remote monitoring centre. In this paper we describe a system of signal acquisition and processing to be used at home and in ambulatory conditions in CHF patients, aimed at providing the necessary information to a clinical decision support system (CDSS).
The CHF patient wears a MagIC (Maglietta Interattiva Computerizzata) wearable device, which consists of a sensorized vest and a portable electronic board. The vest is mainly made of cotton and lycra, and is fully washable. At the thorax level the vest includes two woven electrodes made by conductive fibres so to obtain an ECG lead. The contact between textile electrodes and the thorax is guaranteed by the elastic properties of the garment, without requiring application of gel or of any other medium. The vest also includes a textile-based transducer for the measurement of the chest movements (changes in the thorax volume). Via connections made of conductive fibres, ECG and respiratory signals feed an electronic board (having the size of a small cell phone) firmly placed on the vest through a velcro strip. The electronic board is designed to acquire the signals, store them into a local memory card and transmit them to a PDA or other monitoring stations, which can visualize the incoming data and send them via Wi-Fi to a home or mobile gateway for signal processing and production of the HR and the RespR time series. The HR time series is obtained with a time domain processing using a QRS detector with an adaptive threshold applied to a QRS enhanced signal. The RR intervals are averaged on a specified moving window in order to finally obtain the HR time series with 1 Hz sampling frequency. The RespR time series is obtained with a frequency domain processing in order to minimize the effect of signal artefacts that are usually more evident in the chest movement signal than in the ECG lead. The signal is pre-filtered and transformed in the frequency domain using a STFT (short term Fourier transform) with a moving window progressively advancing with steps of 1 sec. The frequency of the peak of the spectrogram is the RespR that is finally averaged in a window of 8 sec.
The home or mobile gateway is able to pack these data also with other vital signs collected using different devices and to send them in XML format to a central repository where they can be elaborated by the CDSS for detection of early decompensation episodes. The system has successfully overcome a preliminary test phase and it is ready for a more extensive test in a real clinical environment.

(Abstract Control Number: 336)