Antti Vehkaoja

Wireless, Multipurpose In-Home Health Monitoring Platform: Two Case Trials

We propose a general purpose home area sensor network and monitoring platform that is intended for e-Health applications, ranging from elderly monitoring to early homecoming after a hospitalization period. Our monitoring platform is multipurpose, meaning that the system is easily configurable for various user needs and is easy to set up. The system could be temporarily rented from a service company by, for example, hospitals, elderly service providers, specialized physiological rehabilitation centers, or individuals. Our system consists of a chosen set of sensors, a wireless sensor network, a home client, and a distant server. We evaluated our concept in two initial trials: one with an elderly woman living in sheltered housing, and the other with a hip surgery patient during his rehabilitation phase. The results prove the functionality of the platform. However, efficient utilization of such platforms requires further work on the actual e-Health service concepts.

Night-Time EKG and HRV Monitoring With Bed Sheet Integrated Textile Electrodes

A system for unobtrusive night-time electrocardiogram (EKG) and heart rate variability (HRV) monitoring as well as data analysis methods are presented, comparing bed sheet HR and HRV values with corresponding parameters obtained by a reference measurement. Our system uses eight embroidered textile electrodes attached laterally to a bed sheet for measuring bipolar contact EKG from multiple channels. The electrodes are arranged in a line so that at least two adjacent electrodes make sufficient skin contact. The focus of the signal processing development has been on selecting the best measurement channel for further analysis and minimizing the amount of incorrectly detected R-peaks. The test measurements were performed with four healthy men without previously known cardiac disorders and one who frequently had premature ventricular contractions (ectopic beats). For healthy test subjects, an average of 94.9% heartbeat detection coverage was achieved with the system during 29 measurement nights (in total 213.8 h of data). In most cases, the quality of the signal obtained from bed sheet electrodes is good enough for the computer-assisted cardiac arrhythmia detection. Applications for EKG derived RR-interval data include the calculation of HRV parameters that can be utilized in sleep quality analysis and other wellness-related topics as well as sleep apnoea detection.

Wireless Head Cap for EOG and Facial EMG Measurements

A head cap made of fabric for measuring EOG and facial EMG signals is presented. Reusable and easy to use electrodes, embroidered of silver coated thread, are integrated into the cap. A two-way wireless data transmission link operating at license free 2.4 GHz frequency band is used for transferring the 16-bit measurement data, sampled with 1 kHz frequency from six channels at maximum, to the receiver device connected to a PC. Tailored PC software is used for displaying the signals and controlling the measurement parameters. The measurement system is intended for recording facial expressions during human emotion studies but it can also be utilized in computer user interface control. The paper shows preliminary results from EOG and facial EMG measurements

Wearable wireless biopotential measurement device

A light wearable wireless biopotential measurement device built up of commercial components is presented. The device utilizes 868 MHz ISM license free frequency band. Very low noise and good interference rejection is achieved using three electrode differential amplifier design and wireless signal transfer. The device has a possibility of calculating heart rate when ECG signal is measured, and transmitting only the heart rate value while conserving power.

Comparison of HRV parameters derived from photoplethysmography and electrocardiography signals

Heart rate variability (HRV) has become a useful tool in analysis of cardiovascular system in both research and clinical fields. HRV has been also used in other applications such as stress level estimation in wearable devices. HRV is normally obtained from ECG as the time interval of two successive R waves. Recently PPG has been proposed as an alternative for ECG in HRV analysis to overcome some difficulties in measurement of ECG. In addition, PPG-HRV is also used in some commercial devices such as modern optical wrist-worn heart rate monitors. However, some researches have shown that PPG is not a surrogate for heart rate variability analysis. In this work, HRV analysis was applied on beat-to-beat intervals obtained from ECG and PPG in 19 healthy male subjects. Some important HRV parameters were calculated from PPG-HRV and ECG-HRV. Maximum of PPG and its second derivative were considered as two methods for obtaining the beat-to-beat signals from PPG and the results were compared with those achieved from ECG-HRV. Our results show that the smallest error happens in SDNN and SD2 with relative error of 2.46% and 2%, respectively. The most affected parameter is pNN50 with relative error of 29.89%. In addition, in our trial, using the maximum of PPG gave better results than its second derivative.

Miniature Wireless Measurement Node for ECG Signal Transmission in Home Area Network

A miniature wireless node for ECG measurements is presented. The ECG node is designed to be used in various applications including measurement of heart rate during physical exercise and continuous long term measurement of ECG for people assumed having, or being recovering from a cardiac disease. The ECG node is wirelessly connected to a computer using IEEE 802.15.4 based radio protocol. The device sends the measured ECG signal together with additional measurement parameters including battery voltage to the computer, where the ECG signal can be analyzed on-line. The ECG node can operate alone or it can be used as a part of an overall system being designed for monitoring people that are transferred from hospital to home treatment

Is 50 Hz high enough ECG sampling frequency for accurate HRV analysis

With the worldwide growth of mobile wireless technologies, healthcare services can be provided at anytime and anywhere. Usage of wearable wireless physiological monitoring system has been extensively increasing during the last decade. These mobile devices can continuously measure e.g. the heart activity and wirelessly transfer the data to the mobile phone of the patient. One of the significant restrictions for these devices is usage of energy, which leads to requiring low sampling rate. This article is presented in order to investigate the lowest adequate sampling frequency of ECG signal, for achieving accurate enough time domain heart rate variability (HRV) parameters. For this purpose the ECG signals originally measured with high 5 kHz sampling rate were down-sampled to simulate the measurement with lower sampling rate. Down-sampling loses information, decreases temporal accuracy, which was then restored by interpolating the signals to their original sampling rates. The HRV parameters obtained from the ECG signals with lower sampling rates were compared. The results represent that even when the sampling rate of ECG signal is equal to 50 Hz, the HRV parameters are almost accurate with a reasonable error.

Utilization of wireless sensor network for health monitoring in home environment

The health care costs in developed countries are increasing fast due to the aging of the population. In-home monitoring of health is becoming more and more attractive both because of expected cost-savings and technical development of suitable measurement devices and wireless sensor networks. In this paper, we present on-going work about embedding health monitoring devices into ordinary homes. The developed system is targeted both for monitoring elderly and for monitoring rehabilitation after hospitalization period. The paper presents the utilized sensor network implementation, chosen set of sensors for the first test trial, as well as other design choices for the trial. In addition, further objectives about concentrating on one special case, the ubiquitous heart rate measurement, are discussed. Our objective is to install several non-contact heart rate monitors into a home environment. The designed system performed well during the trial. However, some issues, such as sensor addressing in WSN and user identification, will be better taken into account in the next trials.

System for ECG and heart rate monitoring during group training

We present a system for measuring ECG signals simultaneously from multiple persons during a group training session. The system transmits the signals to a coordinating computer where heart rate and other parameters are calculated from the signals. The heart rate values can then be shown for example through a video projector on a large display along with individual information about the training intensity.

Age dependence of arterial pulse wave parameters extracted from dynamic blood pressure and blood volume pulse waves

Atherosclerosis is a significant cause of mortality in the aged population, and it affects arterial wall properties causing differences in measured arterial pulse wave (PW). In this study, both dynamic arterial blood pressure PWs and blood volume PWs are analyzed. The PWs are recorded noninvasively from multiple measurement points from the upper and lower limbs from 52 healthy (22–90-year-old) volunteers without known cardiovascular diseases. For each signal, various parameters earlier proposed in the literature are computed, and 25 different novel parameters are formed by combining these parameters. The results are evaluated in terms of age and heart rate (HR) dependence of the parameters. In general, the results show that 14 out of 25 tested combined parameters have stronger age dependence than any of the individual parameters. The highest obtained linear correlation coefficients between the age and combined parameter and individual parameter equal to 0.85 (