Gabriela Postolache

Physiological Parameters Measurement Based on Wheelchair Embedded Sensors and Advanced Signal Processing

This paper presents a multisensing system with wireless communication capabilities embedded on a smart wheelchair that can measure physiological parameters such as heart rate and respiratory rate in an unobtrusive way. Ballistocardiography (BCG) sensors and a three-axis inertial microelectromechanical system accelerometer are embedded on the seat or in the backrest of the wheelchair and the acquired data are transmitted by Wi-Fi to a laptop computer for advanced data processing and logging. In addition, a 3-D accelerometer with ZigBee communication capability is used to extract information about the users posture. Considering the static and dynamic use of the wheelchair, an extended set of measurements for different utilization scenarios was analyzed. An important part of this paper is focused on BCG noise and artifacts removal and heart rate and respiratory rate accurate estimation from BCG signal using wavelet-based filtering and independent component analysis algorithms. A study on wavelet-based filtering considering different types of mother wavelets and different levels of decomposition was also carried out. In the future, other signals will also be acquired to improve the system capabilities and flexibility.

Vital Signs Monitoring System Based on EMFi Sensors and Wavelet Analysis

The paper presents a monitoring system for non-obtrusive measuring of vital signs such as respiration and heart activity. Two sensing channels including electromechanical film sensors (EMFi sensor) tapped on an office chair are used to obtain the ballistocardiographyc (BCG) signals from human subjects. The conditioning circuits include amplification stages (charge amplifier, programmable gain amplifier) and 20 Hz low-pass and 50 Hz notch active filters used to improve the signal-to-noise ratio (SNR). The gain control and analog-to-digital conversion is performed using a multifunction I/O device USB compatible connected to a laptop PC. The digital processing of the acquired signals is an important part of the work. It includes digital filtering, based on Stationary Wavelet Transform, and signal decomposition, based on Discrete Wavelet Transform, in order to extract the respiration and heart rate based on BCG signal analyze. A practical approach concerning the dependence of the used wavelet type on vital signs estimation accuracy is reported. The results on respiration rate and heart rate using BCG signal and the implemented algorithms are compared with the values of these parameters measured through ECG and spirometry analysis.

Microwave FMCW Doppler radar implementation for in-house pervasive health care system

In recent years, the research in the area of ubiquitous healthcare has intensified. There are many technological advances regarding the development of unobtrusive sensors for cardiac and respiratory activity, but the current scenario is still far away from an everyday life fulfilled with ubiquitous healthcare systems. In this paper, it is described the usage of 24GHz microwave FMCW (frequency modulated continuous wave) Doppler radar (MDR) as one of the main components of a pervasive biomedical system that is part of an assistive environment for the people with less mobility or people with long term health condition. As parts of the present work, in this paper are mentioned the design and implementation of an assistive environment based on a MDR sensor, an experimental study concerning the microwave Doppler radar characteristics and remote sensing of heart rate and breath rate, based on acquisition and processing of the signals delivered by the used radar.

Unobstrusive heart rate and respiratory rate monitor embedded on a wheelchair

A biomedical system embedded on a wheelchair able to measure heart rate, respiratory rate, and the wheelchair motion state is presented. A wireless multi-channel acquisition module is connected to a BCG (ballistocardiography) unit and to an inertial 3-axial MEMS accelerometer based unit. The sensing units are embedded on the seat and backrest of the wheelchair and the acquired data is transmitted through Wi-Fi connection to a remote processing unit expressed by a laptop PC. Considering the different motion situations of the wheelchair when utilized by the user, an important part of the work was focused on BCG noise and artifacts removal as well as to heart rate and respiratory rate accurate estimation from BCG signal using wavelet based filtering and ICA (Independent Component Analysis) algorithms. Experimental results for different scenarios of wheelchair utilization are included in the paper.

New Approach on Cardiac Autonomic Control Estimation Based on BCG Processing

The work presents a biomedical instrument for unobtrusive heart rate variability measurement, using ballistocardiographyc (BCG) signal based on electromechanical film sensors (EMFi sensor). The ballistocardiogram acquired signals from subjects sitting on a chair is processed in order to improve its signal-to-noise ratio (SNR) using adaptive neuronal network filtering. The accuracy of beat-to-beat intervals detection using ballistocardiography was tested by comparing the heart rate obtained by simultaneously monitoring the electrocardiogram (EKG) and pulse frequency in young healthy subjects. The results show no statistically relevant differences between the heart rate obtained by BCG in comparison with EKG and pulse frequency measurement. By including wavelet analysis of the heart rate variability (HRV), the prototype system permits a more natural lifestyle monitoring of physiological parameters.

Acute vagal modulation of electrophysiology of the atrial and pulmonary veins increases vulnerability to atrial fibrillation

Vagal activity is thought to influence atrial electrophysiological properties and play a role in the initiation and maintenance of atrial fibrillation (AF). We evaluated the effects of acute vagal stimulation on atrial conduction, refractoriness of atrial and pulmonary veins (PVs) and inducibility of AF. An open‐chest epicardial approach was performed in New Zealand White rabbits with preserved autonomic innervation. Atrial electrograms were obtained with four unipolar electrodes placed epicardially along the atria (n= 22) and an electrode adapted to the proximal left PV (n= 10). The cervical vagus nerve was stimulated with bipolar platinum electrodes (20 Hz). Epicardial activation was recorded in sinus rhythm, and effective refractory periods (ERPs), dispersion of refractoriness and conduction times from high‐lateral right atrium (RA) to high‐lateral left atrium (LA) and PVs assessed at baseline and during vagal stimulation. Burst pacing (50 Hz, 10 s), alone or combined with vagal stimulation, was applied to the right (RAA) and left atrial appendage (LAA) and PVs to induce AF. At baseline, ERPs were lower in PVs than in LA and LAA, but did not differ significantly from RA and RAA, and there was a significant delay in the conduction time from RA to PVs compared with the activation time from RA to LA (P < 0.01). During vagal stimulation, ERP decreased significantly at all sites, without significant differences in the dispersion of refractoriness, and the atrial conduction times changed from 39 ± 19 to 49 ± 9 ms (RA to PVs; n.s.) and from 14 ± 7 to 28 ± 12 ms (RA to LA; P= 0.01). Induction of AF was reproducible in 50% of cases with 50 Hz and in 82% with 50 Hz combined with vagal stimulation (P < 0.05). During vagal stimulation, AF cycle length decreased at all sites, and AF duration changed from 1.0 ± 0.9 to 14.0 ± 10.0 s (P < 0.01), with documentation of PV tachycardia in three cases. In 70% of the animals, AF ceased immediately after interruption of vagal stimulation. We conclude that in the intact rabbit heart, vagal activity prolongs interatrial conduction and shortens atrial and PV ERP, contributing to the vulnerability to the induction and maintenance of AF. This model may be useful in the assessment of the autonomic influence in the mechanisms underlying AF.

Cardio-respiratory and daily activity monitor based on FMCW Doppler radar embedded in a wheelchair

Unobtrusive monitoring of the cardio-respiratory and daily activity for wheelchair users became nowadays an important challenge, considering population aging phenomena and the increasing of the elderly with chronic diseases that affect their motion capabilities. This work reports the utilization of FMCW (frequency modulated continuous wave) Doppler radar sensors embedded in a manual wheelchair to measure the cardiac and respiratory activities and the physical activity of the wheelchair user. Another radar sensor is included in the system in order to quantify the motor activity through the wheelchair traveled distance, when the user performs the manual operation of the wheelchair. A conditioning circuit including active filters and a microcontroller based primary processing module was designed and implemented to deliver the information through Bluetooth communication protocol to an Android OS tablet computer. The main capabilities of the software developed using Android SDK and Java were the signal processing of Doppler radar measurement channel signals, graphical user interface, data storage and Wi-Fi data synchronization with remote physiological and physical activity database.

Indoor monitoring of respiratory distress triggering factors using a wireless sensing network and a smart phone

A wireless sensing network Bluetooth enabled was designed and implemented for continuous monitoring of indoor humidity and temperature conditions as well as to detect pollutant gases and vapors. The novelty of the work is related to the development of an embedded software using Java2ME technology for a smart phone that materializes a user friendly HMI. Two mobile software modules assure sensor nodes data reading through Bluetooth connection, primary data processing, data storage and alarm generation according with imposed thresholds for air quality parameters. Additional .NET developed software for a Notebook PC platform permits to remotely configure the mobile application and to receive the data logged in the mobile phone. Using the implemented distributed measurement system, including the smart phone, an intelligent assessment of air conditions for risk factor reduction of asthma or chronic obstructive pulmonary disease is carried out. Several experimental results are also included.

Multi-usage of microwave Doppler radar in pervasive healthcare systems for elderly

Health assessment requirements for aging population have accentuated the need of ubiquitous and pervasive e-Health environments. Recently, new implemented embedded vital signs sensors were joined to ubiquitous computation in order to materialize Ubi-Health systems with lower price and augmented interoperability in comparison with traditional clinical instrumentation for in house health status monitoring needs. The work reports the utilization of the smart sensor based on 24GHz microwave FMCW (frequency modulated continuous wave) Doppler embedded in smart objects such as wheelchairs, walkers or crutches used by elderly, that perform cardiorespiratory signs and physical activity monitoring. According to the requirements of sensor identification and wireless data communication between the smart sensor and the advanced signal processing, data logging and web publishing unit, a combination between Bluetooth MAC based identification and Virtual Transducer Electronic Data Sheet was implemented. The system allows vital signs and motor activity monitoring, including gait characterization.

Non-invasive Mobile Homeostasis Instrument

In the paper a mobile instrument for non-invasive homeostasis monitoring with abnormalities automatic notification is presented. The tool is designed for physiological research and clinical practice. A small size, portable measuring system based on a personal digital assistant (PDA) with embedded software component was designed to provide information related with vital bio-signals that characterize the human homeostasis. Using a set of sensors, conditioning blocks, a compact flash acquisition board plug-in PDA and Wi-Fi communication module the system provides information concerning the clinical state to experts through a Health Wireless Network. Thus, the instrument is useful for the patients that need continuous homeostasis monitoring