Eugenijus Kaniusas

Method for continuous nondisturbing monitoring of blood pressure by magnetoelastic skin curvature sensor and ECG

This paper concerns continuous nondisturbing estimation of blood pressure using mechanical plethysmography in connection with standard electrocardiography (ECG). The plethysmography is given by a novel magnetoelastic skin curvature sensor (SC-sensor) applied on the neck over the carotid artery. The sensor consists of a magnetoelastic bilayer partly enclosed by a coil. Bending the bilayer causes large changes of magnetic permeability which can be measured by the coil. The SC-sensor signal and the ECG signal are adaptively processed in order to estimate blood pressure according to a specifically established theoretical model. The model uses estimated vessel radius changes and pulse transit time as parameters. The results show cross correlation coefficients in the range 0.8 up to 0.9 between reference and estimated values of systolic blood pressure, diastolic blood pressure, and systolic/diastolic blood pressure change, whereas the estimation error was below 4 +/- 7 mmHg at rest and increased with the stress level. Limitations of the model applicability are given by a hysteretic behavior of both model parameters due to inert changes in artery stiffness. The SC-sensor and the ECG electrodes cause minimal inconvenience to the patient and offer an approach for a continuous nondisturbing monitoring of blood pressure changes, as being relevant for sleep monitoring or biomechanic feedback

Magnetostrictive amorphous bimetal sensors

The paper describes the application of a magnetostrictive amorphous ribbon (AR) for the detection of bending. In order to increase sensitivity, a bimetal structure is used which consists of AR and a nonmagnetic carrier ribbon. Several methods for the preparation of the bimetal are discussed. Results of the bending sensitivities are given for various combinations of the material types indicating crucial problems of bimetal preparation.

Acoustical signal properties for cardiac/respiratory activity and apneas

Traditionally, auscultation is applied to the diagnosis of either respiratory disturbances by respiratory sounds or cardiac disturbances by cardiac sounds. In addition, for sleep apnea syndrome diagnosis, snoring sounds are also monitored. The present study was aimed at synchronous detection of all three sound components (cardiac, respiratory, and snoring) from a single spot. The sounds were analyzed with respect to the cardiorespiratory activity, and to the detection and classification of apneas. Sound signals from 30 subjects including 10 apnea patients were detected by means of a microphone connected to a chestpiece which was applied to the heart region. The complex nature of the signal was investigated using time, spectral, and statistical approaches, in connection with self-defined time-based and event-based characteristics. The results show that the obstruction is accompanied by an increase of statistically relevant spectral components in the range of 300 to 2000 Hz, however, not within the range up to 300 Hz. Signal properties are discussed with respect to different breathing types, as well as to the presence and the type of apneas. Principal component analysis of the event-based characteristics shows significant properties of the sound signal with respect to different types of apneas and different patient groups, respectively. The analysis reflects apneas with an obstructive segment and those with a central segment. In addition, aiming for an optimum detection of all three sound components, alternative regions on the thorax and on the neck were investigated on two subjects. The results suggest that the right thorax region in the seventh intercostal space and the neck are optimal regions. It is concluded that for patient assessment, extensive acoustic analysis offers a reduction in the number of required sensor components, especially with respect to compact home monitoring of apneas.

A magnetostrictive acceleration sensor for registration of chest wall displacements

Abstract The present study concerns a novel acceleration sensor built up using a bimetallic strip with one freely oscillating end. The strip consists of a magnetostrictive amorphous ribbon glued on a nonmagnetic metal ribbon. The sensor’s effectiveness is demonstrated for the case of chest wall displacements as resulting from cardiorespiratory activity. The cheap and easy-to-handle novel sensor offers multiple information on the so-called sleep apnea syndrome.

Magnetostrictive amorphous bilayers and trilayers for thermal sensors

Abstract The study concerns agglutinated bilayers as thermal sensors. Different thermal expansion coefficients of the bilayer—a magnetostrictive amorphous ribbon and a non-magnetic metal counter ribbon—yield mechanical stress of the first by temperature change and thus a change of permeability. The sensitivity is of the order 1% permeability change per Kelvin which can be increased by preventing bilayer bending.

User demands for sensory feedback in upper extremity prostheses

This paper presents the results of 108 responses to a survey asking users of electrical upper limb prostheses about sensory feedback. The survey aimed to identify whether sensory feedback was of interest to users, which kinds of information were important and what feedback modality would be suited for transfer of information. Moreover the situations in which sensory feedback would be most useful should be identified. To answer these questions we designed a survey which was sent by mail and was also available online. 88% of respondents placed different degree of importance on obtaining sensory feedback from their prosthesis. Grip force was most important followed by proprioceptive information. First contact during grasping and end of contact during release of an object was also of interest to respondents. Vibration, pressure and electrical stimulation were identified as appropriate means for transmission of sensory information from the prosthesis to the amputee, based on their acceptance and sensitivity at the residual limb. These findings allow conclusions for further development on what information has to be measured by feedback prostheses and how this information can be transmitted to the amputee. Investigation of perceptions respondents apply to control their current electrical prosthesis reveals that observation, listening and sensations at the residual limb are used and applied to gain certain information about the prosthesis. This could be the basis for a training of prosthesis users aiming at prosthesis control with less visual attention.

Fully Implantable Multi-Channel Measurement System for Acquisition of Muscle Activity

This paper presents intramuscular electromyogram (EMG) signals obtained with a fully implantable measurement system that were recorded during goal directed arm movements. In a first implantation thin film electrodes were epimysially implanted on the deltoideus of a rhesus macaque and the encapsulation process was monitored by impedance measurements. Increase of impedance reached a constant level after four weeks indicating a complete encapsulation of electrodes. EMG recorded with these electrodes yielded a signal-to-noise ratio of about 80 dB at 200 Hz. The EMG recorded during goal-directed arm movements showed a high similarity to movements in the same direction and at the same time presented clear differences between different movement directions in time domain. Six classifiers and seven time and frequency domain features were investigated with the aim of discriminating the direction of arm movement from EMG signals. Reliable recognition of arm movements was achieved for a subset of the movements under investigation only. A second implantation of the whole measurement system for nine weeks demonstrated simple handling during surgery and good biotolerance in the animals.

Automatic multimodal detection for long-term seizure documentation in epilepsy

OBJECTIVE This study investigated sensitivity and false detection rate of a multimodal automatic seizure detection algorithm and the applicability to reduced electrode montages for long-term seizure documentation in epilepsy patients. METHODS An automatic seizure detection algorithm based on EEG, EMG, and ECG signals was developed. EEG/ECG recordings of 92 patients from two epilepsy monitoring units including 494 seizures were used to assess detection performance. EMG data were extracted by bandpass filtering of EEG signals. Sensitivity and false detection rate were evaluated for each signal modality and for reduced electrode montages. RESULTS All focal seizures evolving to bilateral tonic-clonic (BTCS, n=50) and 89% of focal seizures (FS, n=139) were detected. Average sensitivity in temporal lobe epilepsy (TLE) patients was 94% and 74% in extratemporal lobe epilepsy (XTLE) patients. Overall detection sensitivity was 86%. Average false detection rate was 12.8 false detections in 24h (FD/24h) for TLE and 22 FD/24h in XTLE patients. Utilization of 8 frontal and temporal electrodes reduced average sensitivity from 86% to 81%. CONCLUSION Our automatic multimodal seizure detection algorithm shows high sensitivity with full and reduced electrode montages. SIGNIFICANCE Evaluation of different signal modalities and electrode montages paces the way for semi-automatic seizure documentation systems.

Fundamentals of Biosignals

Sensing technologies in physiology gain a lot of importance for the assessment of the human functional state. The registered biomedical signals—referred to as biosignals here—are important not only for timeless classical applications concerning medical diagnosis and subsequent therapy, but also for future applications such as daily driver monitoring.

Magnetoelastic skin curvature sensor for biomedical applications

The present paper concerns the versatile applicability of a novel skin curvature sensor family for multiparametric monitoring of physiological parameters. The basic element of the sensor is a magnetoelastic bilayer which shows a magnetoelastic amorphous layer and a nonmagnetic layer. Bending the bilayer causes the magnetoelastic layer to experience either tensile or compressive stress, depending on the direction of bending. The resulting large changes of magnetic permeability can be measured using a coil. The extreme thinness of the sensor favors its application on the skin in various medical diagnostic areas. On the neck and on the chest wall, the sensor registers cardiorespiratory activity and interrupted breathing, both being relevant for the so-called sleep apnea syndrome. Registration of leg movements is demonstrated on the calf for the diagnosis of the restless leg syndrome. Assessment of eye movements is shown using a miniature sensor version.