Giedrius Varoneckas

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

Management of obstructive sleep apnea in Europe

OBJECTIVES In Europe, the services provided for the investigation and management of obstructive sleep apnoea (OSA) varies from country to country. The aim of this questionnaire-based study was to investigate the current status of diagnostic pathways and therapeutic approaches applied in the treatment of OSA in Europe, qualification requirements of physicians involved in diagnosis and treatment of OSA, and reimbursement of these services. METHODS Two questionnaires were sent to 39 physicians in 22 countries in Europe. In order to standardize the responses, the questionnaire was accompanied by an example. RESULTS Sleep centers from 21 countries (38 physicians) participated. A broad consistency among countries with respect to the following was found: pathways included referral to sleep physicians/sleep laboratories, necessity for objective diagnosis (primarily by polysomnography), use of polygraphic methods, analysis of polysomnography (PSG), indications for positive airway pressure (PAP) therapy, application of standard continuous PAP (CPAP) therapy (100% with an CPAP/APAP ratio of 2.24:1), and the need (90.5%) and management of follow-up. Differences were apparent in reimbursement of the diagnostic procedures and follow-up, in the procedures for PAP titration from home APAP titration with portable sleep apnea monitoring (38.1%) up to hospital monitoring with PSG and APAP (85.7%), and in the qualification requirements of sleep physicians. CONCLUSIONS Management of OSA in different European countries is similar except for reimbursement rules, qualification of sleep specialists and procedures for titration of the CPAP treatment. A European network (such as the one accomplished by the European Cooperation in Science and Technology [COST] B26 Action) could be helpful for implementing these findings into health-service research in order to standardize management in a cost effective perspective.

Insomnia symptoms and mortality: a register‐linked study among women and men from Finland, Norway and Lithuania

Evidence on the association between insomnia symptoms and mortality is limited and inconsistent. This study examined the association between insomnia symptoms and mortality in cohorts from three countries to show common and unique patterns. The Finnish cohort comprised 6605 employees of the City of Helsinki, aged 40–60 years at baseline in 2000–2002. The Norwegian cohort included 6236 participants from Western Norway, aged 40–45 years at baseline in 1997–1999. The Lithuanian cohort comprised 1602 participants from the City of Palanga, aged 35–74 years at baseline in 2003. Mortality data were derived from the Statistics Finland and Norwegian Cause of Death Registry until the end of 2012, and from the Lithuanian Regional Mortality Register until the end of 2013. Insomnia symptoms comprised difficulties initiating sleep, nocturnal awakenings, and waking up too early. Covariates were age, marital status, education, smoking, alcohol, physical inactivity, obesity, diabetes, cardiovascular diseases, depression, shift work, sleep duration, and self‐rated health. Cox regression analysis was used. Frequent difficulties initiating sleep were associated with all‐cause mortality among men after full adjustments in the Finnish (hazard ratio 2.51; 95% confidence interval 1.07–5.88) and Norwegian (hazard ratio 3.42; 95% confidence interval 1.03–11.35) cohorts. Among women and in Lithuania, insomnia symptoms were not statistically significantly associated with all‐cause mortality after adjustments. In conclusion, difficulties initiating sleep were associated with mortality among Norwegian and Finnish men. Variation and heterogeneity in the association between insomnia symptoms and mortality highlights that further research needs to distinguish between men and women, specific symptoms and national contexts, and focus on more chronic insomnia.

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.

Optic Visualization of Auricular Nerves and Blood Vessels: Optimisation and Validation

Auricular blood vessels can be visualized by transillumination of the auricular tissue. The optimisation and validation of the optic visualization are the main subject of this work. Since blood vessels and nerve fibers can be found along one another, the transillumination reveals locations of auricular nerves to unaided human eye. The visualization of the nerves is needed by physicians to precisely insert needles into the auricle for electrical stimulation of auricular nerves. The stimulation is applied to relieve chronic pain and normalize vital physiological parameters. Theoretical approaches are shortly considered which are related to light absorption coefficients of different auricular tissue types and coefficient changes over wavelength. The theory predicts optimal optical contrasts if green and blue colors of light are applied. An experimental validation has been carried out using a novel transillumination device, a finger thimble, among young and elderly, male and female; in total 22 volunteers. Complementary experimental approaches have confirmed theoretical reasoning and have been used to optimize the optical contrast and applied color mixture even further.

Effects of the auricular electrical stimulation on heart rate variability assessed in phase space: Pilot study

The electrical punctual stimulation (P-Stim) of the vagal nerve in the ear is a new stimulation technique for pain relief therapy. A few studies exist regarding the effects of the P-Stim, considering mainly subjective pain relief. In this pilot study we assess objectively the vagal effects of the P-Stim by the appropriate heart rate variability analysis reflecting vagal activity of the autonomous nerve system. In particular, the variability was investigated in the phase space by the recurrence quantification analysis. The results have shown a more deterministic and less divergent heart rhythm not only during the stimulation period but also afterwards, which indicates temporally sustainable effects of the P-Stim.

Embedded Electrocardiographic Amplifier without Reference Electrode

The present paper introduces a patient-friendly embedded electrographic (ECG) amplifier. In contrast to the standard ECG amplifier, the presented system uses only two electrodes to insure unobtrusiveness and compact design. The abandoned third reference electrode and required low power consumption introduce problems in ECG signal preamplification and handling. In order to meet them, a novel adaptive cancellation of 50 Hz power line interference in combination with gain/attenuation controlling is designed and implemented. In particular, the interference is reduced by the use of a self-generated 50 Hz signal with an adoptively adjusted amplitude and phase. On the other hand, the gain/attenuation of the ECG signal is controlled in a way that the range of the analog-to-digital converters is efficiently used. The introduced ECG amplifier without the reference electrode facilitates the portable minimally obtrusive monitoring with potential possibilities of on-site diagnosis

Cardiovascular Oscillations of the Carotid Artery Assessed by Magnetoelastic Skin Curvature Sensor

The present study concerns the nondisturbing assessment of cardiovascular oscillations of the carotid artery using a novel skin curvature sensor on the neck. The mechanical oscillations of the skin reflect changes of the artery radius and thus relevant physiological data such as cardiac and respiratory activities, their mutual dependencies, and even changes of blood pressure. The skin curvature sensor is easy to handle and it minimally disturbs the patient, which is relevant for many medical areas such as sleep monitoring.

Optic visualisation of auricular blood vessels

Optic visualization of auricular blood vessels is considered using transillumination. Since the vessels and nerves course alongside one another, the locations of the nerves are disclosed. The visualization of the nerves is needed for a precise needle application by physician within the scope of electrical stimulation of auricular nerves; the stimulation being applied for pain relieve. Theoretical approaches are considered based on light absorption coefficients over wavelength of different auricular tissue types, which predict optimal optical contrasts for green and blue light. Complementary experimental approaches are introduced which statistical results have proved theoretical reasoning.

Correlations in heart beat data as quantitative characterization of heart pathology

Correlation between heart pathology and statistical properties of heart beat data has been studied. It is shown that heart beat data has different scaling behavior for healthy and disease cases. Possibilities to develop new monitoring technique based on the permanent control of the correlations in heart beat data are discussed.