A. Bolz

CAALYX: a new generation of location-based services in healthcare

Recent advances in mobile positioning systems and telecommunications are providing the technology needed for the development of location-aware tele-care applications. This paper introduces CAALYX – Complete Ambient Assisted Living Experiment, an EU-funded project that aims at increasing older peoples autonomy and self-confidence by developing a wearable light device capable of measuring specific vital signs of the elderly, detecting falls and location, and communicating automatically in real-time with his/her care provider in case of an emergency, wherever the older person happens to be, at home or outside.

Parameter extraction of ECG signals in real-time.

In order for a mobile ECG recorder to be able to classify a heart rhythm online, the significant parameters must be extracted. The relevant parameters are the beginning, peak and end of the QRS-complex, the P- and T-waves, the ST-segment and other significant intervals, such as the RR-interval. The aim of the development was, firstly, stable, real-time-capable QRS detection, which finally achieved values for sensitivity of 98.9% and a positive predictivity of 99.9% on standard ECG databases. Also, a filter-based detection of P- and T-waves was implemented, which can also be performed in real-time on a microcontroller platform.

Real time heart ischemia detection in the smart home care system

In this paper, a novel real-time algorithm for detecting ischemia in the ECG signal is proposed. The goal of this research is to meet the requirements of some smart cardiac home care devices, which can automatically diagnose the ECG and detect the heart risks outside the hospital, especially heart ischemia without symptoms in their early stages. The algorithm is developed based on a real time R peak detector, time domain traditional ECG parameters, the advanced morphologic parameters from Karhunen-Loeve transform, and the adaptive neuro-fuzzy logic classification. Besides, in order to improve the reliability of our algorithm, several significant constraints of the ECG signal are considered. As a result, the ischemia episodes can be detected if the ischemic alteration persists longer than one minute in the ECG signal

Coaxial waveguide MRI

As ultrahigh‐field MR imaging systems suffer from the standing wave problems of conventional coil designs, the use of antenna systems that generate travelling waves was suggested. As a modification to the original approach, we propose the use of a coaxial waveguide configuration with interrupted inner conductor. This concept can focus the radiofrequency energy to the desired imaging region in the human body and can operate at different Larmor frequencies without hardware modifications, as it is not limited by a lower cut‐off frequency. We assessed the potential of the method with a hardware prototype setup that was loaded with a tissue equivalent phantom and operated with imaging areas of different size. Signal and flip angle distributions within the phantom were analyzed, and imaging at different Larmor frequencies was performed. Results were compared to a finite difference time domain simulation of the setup that additionally provides information on the spatial distribution of the specific absorption rate load. Furthermore, simulation results with a human model (virtual family) are presented. It was found that the proposed method can be used for MRI at multiple frequencies, achieving transmission efficiencies similar to other travelling wave approaches but still suffers from several limitations due to the used mode of wave propagation. Magn Reson Med, 2011.

Three different algorithms for identifying patients suffering from atrial fibrillation during atrial fibrillation free phases of the ECG

The paper presents and compares three different methods to detect atrial fibrillation using algorithms. Each of these algorithms can identify patients suffering from atrial fibrillation even if there is no atrial fibrillation visible on the ECG. All methods are based on RR-intervals; thus, only a single channel ECG is required. These algorithms have been tested using the MIT-BIH atrial fibrillation database and the MIT-BIH normal sinus rhythm database. The sensitivity and specificity of method 1 is 91.5% and 96.9% respectively. Method 2 results in a sensitivity of 93.3% and a specificity of 92.8% and method 3 in a sensitivity of 94.1% and a specificity of 93.4%. Even if an atrial fibrillation burden of 0% is assumed, the sensitivity still proves satisfactory (sensitivity of method 1, 2 and 3 is 82.9%, 96.3% and 94.1%, respectively).

Assessment of Changes in Upper Airway Obstruction by Automatic Identification of Inspiratory Flow Limitation During Sleep

New techniques for automatic invasive and noninvasive identification of inspiratory flow limitation (IFL) are presented. Data were collected from 11 patients with full nocturnal polysomnography and gold-standard esophageal pressure (Pes) measurement. A total of 38,782 breaths were extracted and automatically analyzed. An exponential model is proposed to reproduce the relationship between Pes and airflow of an inspiration and achieve an objective assessment of changes in upper airway obstruction. The characterization performance of the model is appraised with three evaluation parameters: mean-squared error when estimating resistance at peak pressure, coefficient of determination, and assessment of IFL episodes. The models results are compared to the two best-performing models in the literature. The obtained gold-standard IFL annotations were then employed to train, test, and validate a new noninvasive automatic IFL classification system. Discriminant analysis, support vector machines, and Adaboost algorithms were employed to objectively classify breaths noninvasively with features extracted from the time and frequency domains of the breathspsila flow patterns. The results indicated that the exponential model characterizes IFL and subtle relative changes in upper airway obstruction with the highest accuracy and objectivity. The new noninvasive automatic classification system also succeeded in identifying IFL episodes, achieving a sensitivity of 0.87 and a specificity of 0.85.

Algorithm for Identifying Patients with Paroxysmal Atrial Fibrillation without Appearance on the ECG

Although atrial fibrillation is the most common sustained cardiac rhythm disturbance, it remains underdiagnosed. One of the most drastic complications is embolism, and strokes in particular. Patients having atrial fibrillation must be identified in order to reduce the number of strokes. The algorithm presented detects atrial fibrillation, even without it being indicated in the analyzed ECG. Based on parameters of heart rate variability, only a 60-minute single channel ECG is required. At first, all R peaks are detected and all RR intervals are calculated. After normalizing the RR intervals, the time domain parameter SDSD is calculated and the so-called Poincare Plot is generated. The image and the time domain analysis assess a risk level, which determines whether the patient is suffering from atrial fibrillation. The resulting sensitivity calculated for ECG recordings from the MIT-BIH atrial fibrillation database is 91.5% and the specificity determined for the ECG recordings from the MIT-BIH normal sinus rhythm database is 96.9%. The sensitivity depends on the atrial fibrillation burden. Even if a burden of 0% is assumed, the results still prove satisfactory (sensitivity nearly 83%).

An Invasive and a Noninvasive Approach for the Automatic Differentiation of Obstructive and Central Hypopneas

The automatic differentiation of obstructive and central respiratory events is a major challenge in the diagnosis of sleep-disordered breathing. Esophageal pressure (Pes) measurement is the gold-standard method to identify these events. This study presents a new classifier that automatically differentiates obstructive and central hypopneas with the Pes signal and a new approach for an automatic noninvasive classifier with nasal airflow. An overall of 28 patients underwent night polysomnography with Pes recording, and a total of 769 hypopneas were manually scored by human experts to create a gold-standard annotation set. Features were automatically extracted from the Pes signal to train and test the classifiers (discriminant analysis, support vector machines, and adaboost). After a significantly (p <; 0.01) higher incidence of inspiratory flow limitation episodes in obstructive hypopneas was objectively, invasively assessed compared to central hypopneas, the feasibility of an automatic noninvasive classifier with features extracted from the airflow signal was demonstrated. The automatic invasive classifier achieved a mean sensitivity, specificity, and accuracy of 0.90 after a 100-fold cross validation. The automatic noninvasive feasibility study obtained similar hypopnea differentiation results as a manual noninvasive classification algorithm. Hence, both systems seem promising for the automatic differentiation of obstructive and central hypopneas.

The technical possibilities in telemonitoring of physiological parameters

SummaryFor decades, telemonitoring of vital parameters has been a recurring topic among experts. Because of its lack of economical advantages it has not established itself as a standard up to now.Thanks to novel wireless communication technologies such as Bluetooth or Zigbee, the enormous technological progress in mobile communication via GSM, GPRS, as well as UMTS and various radical medical changes within disease management programs, currently very promising new potentials for telemonitoring are appearing. This article summarizes the current technological developments, discusses their advantages and drawbacks, and deduces scenarios and technical requirements for future system architectures.ZusammenfassungTelemonitoring von Vitalparametern ist seit vielen Jahrzehnten ein immer wiederkehrendes Thema in der Fachwelt. Bislang hat es sich jedoch mangels ökonomischer Vorteile noch nicht zum Standard durchgesetzt.Dank neuer drahtloser Kommunikationstechnologien wie Bluetooth oder Zigbee, dem enormen technischen Fortschritt in der Mobilkommunikation über GSM, GPRS und UMTS sowie einiger tiefgreifender medizinischer Veränderungen im Rahmen der Disease Management Programme eröffnen sich jedoch aktuell neue Potenziale für das Telemonitoring, die einen Durchbruch versprechen. Der vorliegende Beitrag fasst die aktuellen technischen Entwicklungen zusammen, diskutiert deren Vor- und Nachteile und leitet daraus Szenarien und Anforderungsprofile zukünftiger Systemarchitekturen ab.

Technische Möglichkeiten des Telemonitorings physiologischer Parameter

SummaryFor decades, telemonitoring of vital parameters has been a recurring topic among experts. Because of its lack of economical advantages it has not established itself as a standard up to now.Thanks to novel wireless communication technologies such as Bluetooth or Zigbee, the enormous technological progress in mobile communication via GSM, GPRS, as well as UMTS and various radical medical changes within disease management programs, currently very promising new potentials for telemonitoring are appearing. This article summarizes the current technological developments, discusses their advantages and drawbacks, and deduces scenarios and technical requirements for future system architectures.ZusammenfassungTelemonitoring von Vitalparametern ist seit vielen Jahrzehnten ein immer wiederkehrendes Thema in der Fachwelt. Bislang hat es sich jedoch mangels ökonomischer Vorteile noch nicht zum Standard durchgesetzt.Dank neuer drahtloser Kommunikationstechnologien wie Bluetooth oder Zigbee, dem enormen technischen Fortschritt in der Mobilkommunikation über GSM, GPRS und UMTS sowie einiger tiefgreifender medizinischer Veränderungen im Rahmen der Disease Management Programme eröffnen sich jedoch aktuell neue Potenziale für das Telemonitoring, die einen Durchbruch versprechen. Der vorliegende Beitrag fasst die aktuellen technischen Entwicklungen zusammen, diskutiert deren Vor- und Nachteile und leitet daraus Szenarien und Anforderungsprofile zukünftiger Systemarchitekturen ab.