Jens Krauss

Wrist-located pulse detection using IR signals, activity and nonlinear artifact cancellation

We present a new integrated device for monitoring heart rate at the wrist using an optical measure. Motion robustness is obtained by using accurate motion reference signals of 3D low noise accelerometers together with dual channel optical sensing. Nonlinear modelling allows to remove the motion contributions in the optical signals and the spatial diversity of the sensors is used to remove reciprocal contributions in the two channels. Finally a statistical estimation, based on physiological properties of the heart, gives a robust estimation of the heart rate. Qualitative and quantitative performance evaluation of the performances on real signals clearly show that the proposed system gives an accurate estimation of the heart rate, even under intense physical activity.

Validation of a wrist monitor for accurate estimation of RR intervals during sleep

While the incidence of sleep disorders is continuously increasing in western societies, there is a clear demand for technologies to asses sleep-related parameters in ambulatory scenarios. The present study introduces a novel concept of accurate sensor to measure RR intervals via the analysis of photo-plethysmographic signals recorded at the wrist. In a cohort of 26 subjects undergoing full night polysomnography, the wrist device provided RR interval estimates in agreement with RR intervals as measured from standard electrocardiographic time series. The study showed an overall agreement between both approaches of 0.05 ± 18 ms. The novel wrist sensor opens the door towards a new generation of comfortable and easy-to-use sleep monitors.

Continuous multi-parameter health monitoring system

A concept for continuous multi-parameter health monitoring system is presented. The system can measure and process physiological signals of high medical value, but difficult to measure in an unobtrusive and comfortable ambulatory way. Blood pressure, SpO2, core body temperature, activity, as well as multi-lead ECG and respiration with dry electrodes are addressed. There are only four interfaces with the body, and they are located at the chest. The European Space Agency has mandated CSEM to develop a prototype of its concept for a long-term survey at the Concordia Base Station in the Antarctica, in order to prepare future long-term manned missions. The delivery of the fully functional ready-touse prototype is for mid 2007. This paper outlines the general concept and presents some first experimental results for the SpO2 probe place at the manubrium sterni (upper sternum).

On the reliability of pulse oximetry at the sternum

Non-invasive assessment of arterial oxygen saturation has traditionally been entrusted to pulse oximetry. Whereas commercial probes are confined to the finger tip or the forehead, several recent works aim at enlarging the range of placement sites. In the context of the development of a continuous multi-parameter health monitoring system, CSEM is exploring the reliability of pulse oximetry measurements at the sternum. This talk will address both theoretical and practical aspects of the development of such a sensor with special emphasis on the reliability of the measurement. Experimental data obtained from a novel eight channels sensor will be presented.

Getting rid of the wires and connectors in physiological monitoring

One of the main limitations towards an easy-to-use, comfortable, and reliable product for physiological monitoring comes from wires and associated connectors. Wireless solutions for data transmission are more and more common in every domain, but for biopotential and impedance measurements, at least one galvanic line will always be needed. This paper describes a new technology that can make possible the measurement of biopotentials and body impedances with high quality standard using only one wire. As this wire requires neither shield nor isolation, one can imagine a conductive garment that simply connects several sensors distributed over the body. From the user point of view, the product would be ‘cableless’.

Robust extraction of autonomous nervous profile using a non-invasive method

An improved algorithm for the non-invasive estimation of the autonomous nervous profile is presented. It is based on a previously published method using blind source separation on inter-beat intervals and systolic pressure time series. Improvements focus on robust extraction of cardiovascular parameters and management of singular solutions of blind source separation algorithm. Clinical validation has been performed successfully in 104 experiments on 38 subjects. The method has been finally applied to estimate the autonomic nervous profile during vasovagal syncope, and results have been compared to classical heart rate variability methods.