J. Ottenbacher

Context-aware mobile health monitoring: Evaluation of different pattern recognition methods for classification of physical activity

There are various applications of physical activity monitoring for medical purposes, such as therapeutic rehabilitation, fitness enhancement or the use of physical activity as context information for evaluation of other vital data. Physical activity can be estimated using acceleration sensor-systems fixed on a persons body. By means of pattern recognition methods, it is possible to identify with certain accuracy which movement is being performed. This work presents a comparison of different methods for recognition of daily-life activities, which will serve as basis for the development of an online activity monitoring system.

Integration of a Bluetooth based ECG system into clothing

This article describes the methods used to integrate a Bluetooth based ECG system into a T-Shirt. Some of the components are integrated into the garment, while the flexible electronic system is removable so that the garment can be washed. Technologies that need to be improved for manufacturing smart clothes were identified.

Reliable motion artifact detection for ECG monitoring systems with dry electrodes

Reliable signals are the basic prerequisite for most mobile ECG monitoring applications. Especially when signals are analyzed automatically, capable motion artifact detection algorithms are of great importance. This article presents different artifact detection algorithms for ECG systems with dry electrodes. The algorithms are based on the measurement of additional parameters that are correlated with the artifacts. We describe a mobile measurement system and the procedure used for the evaluation of these algorithms. The algorithms are assessed based upon their effect on QRS detection. The best algorithm improved sensitivity (Se) from 98.7% to 99.8% and positive predictive value (+P) from 98.3% to 99.9%, while 15% of the signal was marked as artifact. This corresponds to a decrease in false positive and false negative detected beats by 89.9%. Different metrics to evaluate the performance of an artifact detection algorithm are presented.

Motion Artefacts in Capacitively Coupled ECG Electrodes

Various applications for capacitive ECG measurement are currently topic of research, several systems to demonstrate the feasibility of contactless measurement have been implemented by different research groups. One problem common to all approaches is the sensitivity to motion artefacts due to relative movement between the body and the measurement system. This paper presents an analysis of motion artefacts in capacitively coupled ECG measurement. A capacitive electrode has been modeled in order to investigate and simulate the time domain behavior and the influence of movements on the output signal. The analysis offers different approaches to reduce these artefacts and a model is presented that allows for artefact correction and reconstruction of the original ECG signal even for artefacts within the ECG spectrum.

An approach to reliable motion artifact detection for mobile long-term ECG monitoring systems using dry electrodes

The authors present a research project aiming to develop a context-aware cardiac permanent monitoring system. A significant challenge addressed by this project is to acquire reliable ECG signals with dry electrodes in order to do an automatic analysis und alerting. A method to detect motion artifacts by the simultaneous measurement of electrode/skin-impedance is proposed. Investigations of the correlation of motion artifacts and impedance signal are presented. Results of applying an impedance signal based artifact detection algorithm on QRS detection is shown.

ECG electrodes for a context-aware cardiac permanent monitoring system

The authors present a research project aiming to develop a context-aware cardiac permanent monitoring system. A significant challenge addressed by this project is to provide ECG electrodes that are suitable for permanent use. Because traditional adhesive gel electrodes seem not to be appropriate, two different approaches for electrodes are investigated: dry electrodes and capacitively coupled electrodes. These types of electrodes have been compared, considering signal quality, necessary analog front-ends, motion artifacts, usability for patients and possible implementations of these electrodes. Methods for artifact detection and artifact supression, which can be applied to these electrode types, are presented.

Using DWT for ECG motion artifact reduction with noise-correlating signals

Dealing with motion artifacts in long-term ECG recordings is a big issue. The frequency spectrum of motion artifacts is similar to the frequencies of the QRS complex — the wanted signal in the ECG. The deletion of motion artifacts often leads to a deformation of QRS complexes, too. These risks can be minimized by using a noise-correlating signal as a second channel for artifact reduction. This paper presents an approach using the electrode-skin impedance as a second channel for the reduction of motion artifacts. Using the discrete wavelet transform, motion artifacts can be deleted time and frequency selective. This filter approach leads to an improvement of the automatic QRS detection and decreases the number of false detections by 35 %.

Obtaining Energy Expenditure and Physical Activity from Acceleration Signals for Context-aware Evaluation of Cardiovascular Parameters

This work presents the design and development of an online daily-life activity measurement system. This system has been conceptualized to be used along with other vital parameter sensor-systems, e.g. blood-pressure and electrocardiogram (ECG), to provide the necessary context information for the evaluation of the health status of cardiovascular risk patients who are not hospitalized, but must be permanently monitored during their daily routines. The activity and energy expenditure are captured and estimated from accelerometers, which are placed on different points of the body. The activity, the ECG and the blood pressure are sent to a base station (smart phone or a PDA) and from there to a data base, to which the physicians have access. Thus it is possible to continuously analyze the vital data of a cardiovascular patient taking into consideration the activity or physical strain.

Ambulant ECG Recording with Wet and Dry Electrodes: A Direct Comparison of two Systems

Long-term ECG monitoring has established itself as a standard cardiologic diagnostic method since it allows the detection of rare occurring arrhythmias. Conventional Holter recorders that use wet electrodes have however proven to have the restriction of limited application periods and poor wearing-comfort. Recent approaches have focused to benefiting from the extended durability of dry electrodes and modern smart textile technologies with a view to achieving convenient wearing comfort.

A Mobile Device for Textile-integrated Long-term ECG Monitoring

The widespread adoption of telemedical home monitoring can make a contribution to reduce the costs of health-care systems. In this context cardiac monitoring is expected to become one main field of application. However, to leverage this approach a new generation of monitoring devices is necessary. In this paper we specify the requirements for such a long-term cardiac telemonitoring device, with a focus on the special needs of elderly or diseased people. Afterwards, a system prototype fullfilling these requirements is presented: A garment with integrated dry electrodes has been developed, as well as a low-power processing unit featuring recording and embedded processing of ECG and activity signals. In order to ensure connectivity, wireless data transmission via GPRS has been implemented. A detailed description of the system components and a summary of its properties are given.