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Resource-Constrained Device for Unobtrusive Estimation of Sleep Stages Using R-R Interval Data

Identifying the Sleep stages is an essential component of sleep studies. It is normally done by observing collective behavior of various physiological signals, including EEG, EMG, EOG, etc. Recently it has been demonstrated that respiration and ECG can be computationally augmented to reasonably estimate the sleep stages. This paper describes a dedicated wireless device developed to acquire the cardiorespiratory data to distinguish the sleep stages. The device extracts R-R intervals and respiration data from the ECG and transmits it over the Bluetooth. The miniature hardware device and its energy efficient firmware design, presented in this work, are tested against the standard ECG machine for accuracy of R-R interval periods and ECG derived respiration (EDR). The experimental results show very good agreement of observed data with that obtained using commercial wired machine. The device can be very useful in unobtrusively screening the patients suffering with sleep related problems, especially in an out of center setting.