For many decades the measurement of body core temperature has been ubiquitously established in medical and non-medical applications, e.g., in hospitals, occupational medicine, sports medicine, military and other settings. However, there are still numerous challenges, such as the precise definition of the body core temperature, establishing the clinical importance of the measured temperature and the lack of a reliable, non-invasive and fast measurement method for body core temperature. After an introduction to the topic, the medical aspects from a user point of view are presented, i.e., the needs for temperature measurements, as well as possible measurement sites and clinical specifications and needs are highlighted. Subsequently, technical methods are presented which are used for temperature measurement. The analysis of the technical methods is divided into two sections: the first deals with the standard methods, which are currently used and the second describes methods, which are currently under development. Although temperature measurement appears very easy and is very common in daily use, it has many constraints, which are considered later. The need for further research is deduced from the above-mentioned sections and is finally followed by the conclusions section.

Wearable electronics may become a key element in the future to measure a patient's physiological parameters not only in a clinical environment. This work describes dry electrodes based on conductive rubber, which can be integrated into clothing for monitoring purposes. Characteristic electrical properties like warm up time, skin-electrode impedance and motion artefacts will be discussed.

The paper describes an approach to monitor a person's ECG and activity continuously with functional clothing. A belt with integrated electronics has been developed and has proven long-term robustness of all electrical components. A low-power module measures the ECG signal as well as the acceleration (2-axis) and stores data continuously up to two days. A user test has been performed to evaluate the belt according to system performance at different daily-life activities like sleeping, walking and so on. System parameters are ECG-signal quality, system up-time, and ECG-signal coverage during a day.

Measurement of hemodynamic parameters such as stroke volume (SV) via impedance cardiography (ICG) is an easy, non-invasive and inexpensive way to assess the health status of the heart. We present a possibility to use this technology for monitoring risk patients at home. The IMPACT Shirt (IMPedAnce Cardiography Textile) has been developed with integrated textile electrodes and textile wiring, as well as with portable miniaturized hardware. Several textile materials were characterized in vitro and in vivo to analyze their performance with regard to washability, and electrical characteristics such as skin-electrode impedance, capacitive coupling and subjective tactile feeling. The small lightweight hardware measures ECG and ICG continuously and transmits wireless data via Bluetooth to a mobile phone (Android) or PC for further analysis. A lithium polymer battery supplies the circuit and can be charged via a micro-USB. Results of a proof-of-concept trial show excellent agreement between SV assessed by a commercial device and the developed system. The IMPACT Shirt allows monitoring of SV and ECG on a daily basis at the patient's home.

Impedance cardiography is a simple and inexpensive method to acquire data on hemodynamic parameters. This study analyzes the influence of four dynamic physiological sources (aortic expansion, heart contraction, lung perfusion and erythrocyte orientation) on the impedance signal using a model of the human thorax with a high temporal resolution (125 Hz) based on human MRI data. Simulations of electromagnetic fields were conducted using the finite element method. The ICG signal caused by these sources shows very good agreement with the measured signals (r = 0.89). Standard algorithms can be used to extract characteristic points to calculate left ventricular ejection time and stroke volume (SV). In the presented model, the calculated SV equals the implemented left ventricular volume change of the heart. It is shown that impedance changes due to lung perfusion and heart contraction compensate themselves, and that erythrocyte orientation together with the aortic impedance basically form the ICG signal while taking its characteristic morphology from the aortic signal. The model is robust to conductivity changes of tissues and organ displacements. In addition, it reflects the multi-frequency behavior of the thoracic impedance.

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Heart failure (HF) and atrial fibrillation (AF), emerging as two epidemics of the twenty-first century, are commonly associated with each other. Both have been mechanistically linked to changes in cardiac vagal control. The importance of peripheral chemosensors, located in the carotid body, has not been elucidated so far. We therefore investigated whether tonic activation of excitatory chemoreceptor afferents contributes to the altered vagal control in HF patients with a history of AF. In 18 patients (72 ±9 year, 7 male) with sinus rhythm and a history of AF (n=9, without any evidence of structural heart disease, AF group; n=9 with structural heart disease and clinical presentation of HF, AFHF group) we investigated the impact of chemosensory deactivation (by breathing 100% oxygen) on heart rate, blood pressure, cardiac output, total peripheral resistance, oxygen saturation and breathing rate. Ten healthy individuals served as a control group. In addition, we performed a deep breathing test demonstrating an impaired heart rate variation in patients with and without HF as compared with controls (expiration/inspiration difference: 23.9±6.9 vs. 6.9±6.1 bpm, and 23.9±6.9 vs. 7.8±4.8 bpm; p<0.05). In both control and AF groups, heart rate decreased during chemoreceptor deactivation (control: -4.8±3.4%; AF: -5.1±3.0%; p<0.05), whereas heart rate did not change in AFHF patients. This resulted in impaired cardiac chemoreflex sensitivity in AFHF patients (1.9±1.6 vs. 0.5±1.2 ms/mmHg; p<0.05). In conclusion, our data suggest that tonic activation of excitatory chemoreceptor afferents contributes to a low vagal tone in heart failure patients with a history of AF (Clinical Trials NCT01262508).