Non-Contact Monitoring of ECG in the Home Environment-Selecting Optimal Electrode Configuration.

Capacitive electrocardiography (cECG) is most often used in wearable or embedded measurement systems. The latter is considered in the paper. An optimal electrocardiographic lead, as an individual feature, was determined based on model studies. It was defined as the possibly highest value of the R-wave amplitude measured on the back of the examined person. The lead configuration was also analyzed in terms of minimizing its susceptibility to creating motion artifacts. It was found that the direction of the optimal lead coincides with the electrical axis of the heart. Moreover, the electrodes should be placed in the areas preserving the greatest voltage and at the same time characterized by the lowest gradient of the potential. Experimental studies were conducted using the developed measurement system on a group of 14 people. The ratio of the R-wave amplitude (as measured on the back and chest, using optimal leads) was less than 1 while the SNR reached at least 20 dB. These parameters allowed for high-quality QRS complex detection with a PPV of 97%. For the "worst" configurations of the leads, the signals measured were practically uninterpretable.

Coupling between Blood Pressure and Subarachnoid Space Width Oscillations during Slow Breathing.

The precise mechanisms connecting the cardiovascular system and the cerebrospinal fluid (CSF) are not well understood in detail. This paper investigates the couplings between the cardiac and respiratory components, as extracted from blood pressure (BP) signals and oscillations of the subarachnoid space width (SAS), collected during slow ventilation and ventilation against inspiration resistance. The experiment was performed on a group of 20 healthy volunteers (12 females and 8 males; BMI=22.1±3.2 kg/m2; age 25.3±7.9 years). We analysed the recorded signals with a wavelet transform. For the first time, a method based on dynamical Bayesian inference was used to detect the effective phase connectivity and the underlying coupling functions between the SAS and BP signals. There are several new findings. Slow breathing with or without resistance increases the strength of the coupling between the respiratory and cardiac components of both measured signals. We also observed increases in the strength of the coupling between the respiratory component of the BP and the cardiac component of the SAS and vice versa. Slow breathing synchronises the SAS oscillations, between the brain hemispheres. It also diminishes the similarity of the coupling between all analysed pairs of oscillators, while inspiratory resistance partially reverses this phenomenon. BP-SAS and SAS-BP interactions may reflect changes in the overall biomechanical characteristics of the brain.

Can we rely on the pulse transit time - pressure relationship - models comparison.

An unobtrusive, noninvasive and continuous pressure measurement is invaluable however, still being under research and development. There are many attempts proposing an appropriate relationship between pulse pressure velocity and pressure. Fifteen different formulas, both theoretical and experimental, describing relation between blood pressure and cross-sectional area of the vessel were examined. Using these formulas the relation between blood pressure and pulse transit time were derived. The results obtained show variety of dependences. For some of them an explicit derivation was not possible due to non-linear characteristics of the models. It follows from the study performed that depending on the assumptions accepted, even using the same approach, one can obtain contradictory results.

Respiratory signal of bathing person - preliminary study.

The scope of this paper is analysis of applicability of modern biomedical acquisition system installed in bathtub towards reception of respiratory signals of bathing person. An analysis of the possibility of such measurement is shown as well as preliminary results.

Methodology for assessing end-user requirements in the Ella4Life project: elders' perspectives about self-monitoring.

The purpose of this paper is to explore elders' perspectives about self-monitoring and using specially developed sensor technology for measuring health indicators. The qualitative research method is focus-groups with guidelines that were designed for understanding elder's requirements about monitoring health indicators. We present them two devices: the first sensor is a device for monitoring of cardiac action potential fixed into an armchair, the second sensor for monitoring vital signs is placed in a bathtub. The people express their needs and expectations regarding the idea of having sensors for monitoring health indicators and body movement in their own house.

Electrodes array for contactless ECG measurement of a bathing person - a sensitivity analysis.

An applicability of a remote (contactless) electrocardiogram (ECG) measurements in a bathtub is presented in the paper. Possibility of ECG measurements in shallowly filled tube with a water was examined. A bathing person was, both, sitting and lying during experiments performed. The problem became non-trivial when the bathing person was moving in reference to a fixed set of electrodes and located at the longer walls of the bathtub. However, the results obtained indicate that the sensitivity of a developed electrode array could enable such measurements. However, a spatial sensitivity distribution determines, both, the recorded ECG signal parameters and quality.

A Meta-Analysis of Pulse Arrival Time Based Blood Pressure Estimation.

The paper presents a preliminary meta-analysis of the sample correlation between pulse arrival time (PAT) and blood pressure (BP). The aim of the study was to verify sample correlation coefficient between PAT and BP using an affine model $ BP = a . PAT+b $ for systolic and diastolic blood pressure. The databases included in the search were the IEEE Xplore Digital Library, Springer Link and Google Scholar. Only papers from 2005 to 2017 wereincluded into analysis. The random-effects model was considered. The resulting sample correlation coefficient was equal to -0.82 (95 % CI; -0.89, -0.72) for systolic blood pressure and -0.64 (95% CI, -0.74 -0.51) for diastolic one. Egger's regression test showed that there was no evidence of publication bias. Obtained 95% CI intervals for sample correlation coefficients for SBP and DBP are almost separate, which may indicate different relation between PAT and BP for systolic and diastolic pressure.

A body position influence on ECG derived respiration.

An influence of a human body position on ECG derived respiration (EDR) signal is presented in the paper. Examinations were performed during deep, suspended and normal breathing for eight people in four different body positions. EDR and thoracic impedance signals were compared using correlation and standard deviation coefficients. Obtained results have shown that it is possible to monitor breath activity of people being in different position, however a precise interpretation of the obtained signal is limited.

A novel sensor for measuring temperature profile during the thermoablation.

A novel approach for monitoring a temperature distribution inside a tissue during thermoablation is presented in the paper. A thermal profile is measured using a set of serially connected thermistors each bypassed by a capacitor. This technique allows a two-wire and simultaneous multi-point measurements using a multi-frequency measurement of electrical impedance. It is shown that application signals of appropriately selected frequency allows simultaneous measurement of temperature at five distinct points. This technique can be utilized in the assisting of a thermoablation process, and in other applications based on resistive or capacitive sensors.

Monitoring of myocardium state during off-pump coronary artery by-pass grafting.

A measurement technique for evaluation of processes occurring in the myocardium during blood flow arrest is presented. The system is devoted to monitoring the myocardium state during off-pump coronary artery by-pass grafting, i.e. during a surgical operation performed on a beating heart. A substantial part of the system is a probe whose construction is similar to a mechanical stabilizer. Such a stabilizer is used for preventing the myocardium from moving, thus it enables stitching of the graft and artery. In comparison to the commercially available stabilizer the developed probe is enhanced with a set of electrodes. These electrodes enable simultaneous measurements of impedance and electrograms. Examples of recordings made during in vivo studies are also presented. Thus, the proposed method is applicable and potentially very useful in clinical practice.

A modified cardiac stabilizer used for recording electrograms.

Originally, tissue stabilizer has been developed by Medtronic, Inc. It is used to prevent a certain part of myocardium from moving. For example, such an approach is utilized during Coronary Artery Bypass Grafting (CABG). Moreover, medical procedures during such operations involve blood arrest, thus, potentially may involve ischemia of myocardium. A construction of the modified tissue stabilizer used during surgery on a beating heart is presented in the paper. We have developed a stabilizer that aside preventing part of myocardium from moving enables recording of epicardial electrograms. Four electrograms are recorded simultaneously together with one lead of standard ECG as a reference signal. Time relations between electrograms, recorded at four different points surrounding potentially ischemic area, are strongly modified by processes triggered by myocardium ischemia. Aside a construction of the stabilizer the associated measurement system is also presented. Measurement properties of the developed stabilizer and measurement system have been examined during tank studies. Finally, the waveforms obtained during in vivo study are also presented.

A six-ring probe for monitoring conductivity changes.

This paper presents the construction of a six-ring probe for monitoring immittance changes. The spatial sensitivity of the probe is defined. This is used to examine the uniqueness of the probe in terms of its application to monitoring conductivity changes. A spatial distribution of the sensitivity is presented for isotropic and anisotropic cases. The latter case is restricted only to anisotropy met when measuring muscles, i.e. diagonal anisotropy. Theoretical calculations performed using the finite element method were verified experimentally using a specially developed measuring system. An example of in vivo measurements is included.