Radar-based sleep stage classification in children undergoing polysomnography: a pilot-study.

STUDY OBJECTIVES: Unobtrusive monitoring of sleep and sleep disorders in children presents challenges. We investigated the possibility of using Ultra-Wide band (UWB) radar to measure sleep in children. METHODS: Thirty-two children scheduled to undergo a clinical polysomnography participated; their ages ranged from 2 months to 14 years. During the polysomnography, the children's body movements and breathing rate were measured by an UWB-radar. A total of 38 features were calculated from the motion signals and breathing rate obtained from the raw radar signals. Adaptive boosting was used as machine learning classifier to estimate sleep stages, with polysomnography as gold standard method for comparison. RESULTS: Data of all participants combined, this study achieved a Cohen's Kappa coefficient of 0.67 and an overall accuracy of 89.8% for wake and sleep classification, a Kappa of 0.47 and an accuracy of 72.9% for wake, rapid-eye-movement (REM) sleep, and non-REM sleep classification, and a Kappa of 0.43 and an accuracy of 58.0% for wake, REM sleep, light sleep and deep sleep classification. CONCLUSION: Although the current performance is not sufficient for clinical use yet, UWB radar is a promising method for non-contact sleep analysis in children.

An improved system approach towards future cochlear implants.

Cochlear implants (CIs) have been used for many years to restore hearing for deaf patients. Unfortunately, today's CIs are still bulky devices and uncomfortable to wear. In this paper we present three innovations that ultimately should pave the way to a fully implantable bionic ear. First a microfabrication process used to fabricate the polymer metal microelectrode array for auditory nerve stimulation is discussed. Subsequently, a compact biphasic programmable stimulator chip to be used along with this electrode array is presented. By using a double loop feedback circuit topology, the circuit provides a precise stimulation current while requiring only little voltage headroom. The resulting low power consumption and reduced chip area allow for integration of the electronic circuitry onto the electrode array. Finally, as reliability and data transmission rate are two of the most critical issues in CI devices, we propose a software method to improve both data rate and reliability of transmitting digital data from the external part of the CI to the internal part with negligible power consumption.

Multiwavelet design for cardiac signal processing.

An approach for designing multiwavelets is introduced, for use in cardiac signal processing. The parameterization of the class of multiwavelets is in terms of associated FIR polyphase all-pass filters. Orthogonality and a balanced vanishing moment of order 1 are built into the parameterization. An optimization criterion is developed to associate the wavelets with different meaningful segments of a signal. This approach is demonstrated on the simultaneous detection of QRS-complexes and T-peaks in ECG signals.