Comparison of Temporal and Spectral Properties of EMFi and SCSB Signals

J.I. Alametsä, A.J. Saastamoinen, E.J. Huupponen, A.O. Värri, A.S. Joutsen, J. Hasan, E.R. Rauhala, and S.-L.J. Himanen (Finland)


EMFi, SCSB, BCG, apnea, sleep research


In this paper we describe methods developed and applied for comparing temporal and spectral properties of signal from an Electromechanical Film (EMFi) sensor and signal from a Static Charge Sensitive Bed (SCSB) mattress in order to evaluate the different properties of these sensors and their suitability for sleep studies. The SCSB mattress has been used earlier in sleep research for simultaneous recordings of respiration, BCG (ballistocardiogram) and movements in order to detect different sleep disorders like apneas and for sleep scoring. Nowadays also the EMFi sheet has shown potential in sleep recordings. For this study a single simultaneous recording was made from one person with SCSB mattress and EMFi sheet and three signal analysis methods were developed in order to compare obtained signals in suppressed respiration and in normal respiration. Measures of amplitude similarity, correlation degree and spectral similarity were studied. Comparisons between EMFi and SCSB signals produced high similarity with all three comparison methods. During both suppressed and unsuppressed respiration, amplitude similarity and correlation were quite close to each other. In spectral comparison the EMFi and SCSB signals were very similar in the frequency range 616 Hz during both suppressed and unsuppressed respiration. In 0-16 Hz frequency range the similarity was higher during suppressed respiration.

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