Abstract— In this paper, we present a home device for the continuous monitoring of sleep and investigate its reliability regarding sleep evaluation. The system has been particularly designed for healthy people and for preventive purposes. It is not obtrusive and therefore can be used every night without impeding sleep in itself and without interfering with the normal way of life. The signal used for sleep evaluation is the HRV derived from the ECG recorded by means of a sheet and a pillow. Patients in a sleep lab and healthy subjects at home were monitored during sleep with the textile system, while also standard ECG and respiration were recorded. For the textile ECG sensor, coverage of the signal on a beat-to-beat basis ranged from 47,9 – 95,8% of the overall night for the healthy subjects, with a mean coverage of 81,8%. In the group of sleep laboratory patients, the mean coverage was lower - 64,4% - although even in this group the coverage of a single night ranged up to 98.4%. After frequency analysis, the spectral parameters used for sleep staging and derived at the same time from standard and textile ECG signals were compared. The trends along the night are very similar, indicating the possibility of using textile HRV for sleep evaluation. I. INTRODUCTION N previous papers we demonstrated the possibility of providing indices on the quality of sleep in healthy subjects from the heart rate variability (HRV) signal [1-3]. It is well known that the quality of sleep has a great impact on daily life and on the performance one can obtain at work, in sports, etc. Daytime somnolence can be the cause of serious incidents at work or while driving. Further, many researchers have proven how sleep deprivation or a bad quality of sleep for prolonged periods could be related to the rise of hypertension, cardiovascular pathologies, obesity, diabetes and to a decrease in the efficiency of the immune system [4]. For all those reasons, an indication on the sleep quality may really constitute a good parameter for prevention also in healthy subjects. However, the usual tool for a complete sleep evaluation is the polysomnography that requires a well-equipped laboratory in a sleep clinic and specialized medical personnel. Thus only people with well-defined Manuscript received April 16, 2007. This work was supported in part by the MyHeart Project IST 507816 of the European Community. A. M. Bianchi, M. O. Mendez, S. Cerutti are with the Department of Biomedical Engineering of the Polytechnic University in Milan, Italy (e- mail: annamaria.bianchi@polimi.it) S. Devot, E. Naujokat and A. Brauers are with Philips Research Europe, Weisshausstrasse 2, 52066 Aachen, Germany (e-mail: sandrine.devot@philips.com) . symptoms are assigned to such an evaluation, which is not indicated for prevention because of its costs, the need of at least one night in the clinic, and the limited number of sleep centers. In this paper we present a home device for the continuous monitoring of sleep that was particularly designed for healthy people. The system is not obtrusive and can be used every night without impeding sleep in itself and therefore without interfering with the normal way of life. A similar device for monitoring ECG during sleep has been already proposed by [5]. In the present work we address the problem of obtaining a reliable sleep evaluation from the HRV signal derived from the ECG signal recorded by means of a textile sheet and pillow and discuss the accuracy of the estimated HRV parameters. II. METHODS Sleep is a physiological condition mainly involving the Central Nervous System (CNS), and is usually studied through the EEG signal associated with EMG and EOG. The classical sleep staging, according to [6], is based on those signals, as well as the identification of other relevant events, such as microarousals, CAP sleep, etc. However, it is well known that also the Autonomic Nervous System (ANS) is strongly affected by the status of the CNS and many researchers testify the presence of autonomic changes related to different sleep stages [7]. The influence of the ANS produces spontaneous fluctuations in blood pressure and in heart rate, which can be highlighted and quantified by the frequency domain analysis of the heart rate variability signal. It is generally accepted that three main components contribute to HRV: • the very low frequency (VLF) component is assumed to be due to long-term regulatory mechanisms such as humoral factors, temperature, and other slow components; • the rhythm corresponding to vasomotor waves, which is present in heart period and arterial pressure variabilities is defined as the low frequency (LF) component. Since it increases during sympathetic stimulation, it can be considered as a marker of sympathetic activation; • the respiratory rhythm, synchronous with the respiration rate, defined as the high frequency (HF) component, is generally considered as a marker of vagal modulation. A reciprocal relation does exist between the power of the LF and HF rhythms. This balance can be quantified by the LF/HF ratio [8, 9]. Sleep Monitoring Through a Textile Recording System Sandrine Devot, Anna M. Bianchi, Member IEEE, Elke Naujokat, Martin O. Mendez, Andreas Brauers, and Sergio Cerutti, Member IEEE I Proceedings of the 29th Annual International Conference of the IEEE EMBS Cité Internationale, Lyon, France August 23-26, 2007. FrB01.4 1-4244-0788-5/07/$20.00 ©2007 IEEE 2560