A Wireless Device for Ambulatory Cardiac and Respiratory Monitoring - Design Considerations and Essential Performance

In recent years, utilization of mobile devices for tracking health parameters has increased. These devices are able to monitor different parameters such as heart rate, respiration patterns, amount of activity and energy expenditure. The devices specialized for medical applications provide more accurate measurements, assisting medical decision-makings and diagnosis procedures. This thesis work presents the development of an ambulatory health monitoring system for measuring heart activity, respiration and movement. The developed system consists of a measurement unit, an Android application and a computer software. The measurement device, along with capturing the data from the required sensors, is also able to locally store and/or transmit the data wirelessly to a hand-held device. The designed Android application is responsible for receiving this data, reconstructing it and visualizing it in real-time. The computer software is developed to extract the locally stored information after the recordings. The electronic design of the measurement unit is thoroughly described and the limitations are explored. Additionally, the structure of the implemented embedded software is illustrated and justified. Some brief overview of the structure of the Android application and the computer software is also provided. The signal quality achieved by the system was evaluated and the power consumption was measured for different use cases. Our results showed that the developed system provides a competing signal quality comparing to devices in the market. Additionally, it has been shown that transmitting the data via Bluetooth Smart is less power hungry than storing it to a memory card. The report is finalized by mentioning the challenges faced during the development process

Evaluation of Dry Electrodes in Canine Heart Rate Monitoring

The functionality of three dry electrocardiogram electrode constructions was evaluated by measuring canine heart rate during four different behaviors: Standing, sitting, lying and walking. The testing was repeated (n = 9) in each of the 36 scenarios with three dogs. Two of the electrodes were constructed with spring-loaded test pins while the third electrode was a molded polymer electrode with Ag/AgCl coating. During the measurement, a specifically designed harness was used to attach the electrodes to the dogs. The performance of the electrodes was evaluated and compared in terms of heartbeat detection coverage. The effect on the respective heart rate coverage was studied by computing the heart rate coverage from the measured electrocardiogram signal using a pattern-matching algorithm to extract the R-peaks and further the beat-to-beat heart rate. The results show that the overall coverage ratios regarding the electrodes varied between 45-95% in four different activity modes. The lowest coverage was for lying and walking and the highest was for standing and sitting.Peer reviewe

A Wireless Device for Ambulatory Cardiac and Respiratory Monitoring - Design Considerations and Essential Performance

In recent years, utilization of mobile devices for tracking health parameters has increased. These devices are able to monitor different parameters such as heart rate, respiration patterns, amount of activity and energy expenditure. The devices specialized for medical applications provide more accurate measurements, assisting medical decision-makings and diagnosis procedures. This thesis work presents the development of an ambulatory health monitoring system for measuring heart activity, respiration and movement. The developed system consists of a measurement unit, an Android application and a computer software. The measurement device, along with capturing the data from the required sensors, is also able to locally store and/or transmit the data wirelessly to a hand-held device. The designed Android application is responsible for receiving this data, reconstructing it and visualizing it in real-time. The computer software is developed to extract the locally stored information after the recordings. The electronic design of the measurement unit is thoroughly described and the limitations are explored. Additionally, the structure of the implemented embedded software is illustrated and justified. Some brief overview of the structure of the Android application and the computer software is also provided. The signal quality achieved by the system was evaluated and the power consumption was measured for different use cases. Our results showed that the developed system provides a competing signal quality comparing to devices in the market. Additionally, it has been shown that transmitting the data via Bluetooth Smart is less power hungry than storing it to a memory card. The report is finalized by mentioning the challenges faced during the development process

A review of transient suppression methods of IIR notch filters used for power-line interference rejection in ECG measurement

Bioelectric signals are often corrupted by noise. The most common form of noise is power-line interference and its harmonics. A convenient way for eliminating these unwanted components is to use a single or multiple notch filters. One of the problems about this approach is the effect of transient response of the filter at the beginning of its output in short time measurements. In this work, three initialization methods, which can be used to reduce/overcome this problem are reviewed and their performance and computational complexity are evaluated using ECG as an example signal. These methods are projection initialization, pole radius-varying filtering and vector projection. Additionally, some implementation variations and memory usage considerations are discussed. Our study shows that, pole radius-varying method is computationally cheap but introduces longer transient than the others. On the other hand, vector projection provides a more accurate reconstruction of the signal in the transient part of the output but with a more expensive computation. There are also two drawbacks about vector projection. One is its computational complexity dependency to the sampling frequency of the signal and the other is the fact that it cannot provide the results in real-time.acceptedVersionPeer reviewe

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.acceptedVersionPeer reviewe

Comparison of Simple Algorithms for Estimating Respiration Rate from Electrical Impedance Pneumography Signals in Wearable Devices

Respiration rate (RR) is considered as a useful parameter in characterizing the health condition of a person. Among the methods used for respiration measurement, Electrical Impedance Pneumography (EIP) can be easily obtained in wearable applications due to the possibility of using the electrocardiography (ECG) electrodes for the EIP measurement. In the fast growing field of wearable devices, having clinically valuable and reliable information along with providing the convenience of the user, is probably the most important and challenging issue. To address the need of small sized devices for ECG (and EIP) measurements, EASI electrode configuration is an acceptable solution. The signals from EASI system not only provide useful information by themselves when directly used for cardiological analyses, but can also be converted to the standard 12-lead ECG information. With aforementioned advantages of EASI system, the question then arises how suitable the electrode locations of the system are for EIP measurements and what algorithms perform better for respiration rate derivation. In this work, we evaluated eight methods for deriving respiration rate from EIP signals measured from 15 subjects (10 males +5 females) in three conditions: standing, walking slowly, and walking fast. The algorithms were autoregressive (AR) modeling (three different approaches), Fast Fourier Transform (FFT), autocorrelation, peak detection and two counting algorithms. Our results show that advanced counting method is the most promising approach among the ones studied in this work. For this algorithm, the concordance correlation coefficients of the respiration rate estimates between EIP and the reference measurement were 0.96, 0.90 and 0.97 for standing, walking with 3 km/h speed, and walking with 6 km/h speed, respectively.acceptedVersionPeer reviewe

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.acceptedVersionPeer reviewe

Printed soft-electronics for remote body monitoring

Wearable electronics has emerged into the consumer markets over the past few years. Wrist worn and textile integrated devices are the most common apparatuses for unobtrusive monitoring in sports and wellness sectors. Disposable patches and bandages, however, represent the new era of wearable electronics. Soft and stretchable electronics is the enabling technology of this paradigm shift. It can conform to temporary transfer tattoo and deform with the skin without detachment or fracture. In this paper, we focus on screen-printed soft-electronics for remote body monitoring. We will present a fabrication process of a skin conformable electrode bandage designed for long-term outpatient electrocardiography (ECG) monitoring. The soft bandage is designed to be attached to the patient chest and miniaturized data collection device is connected to the bandage via Micro-USB connector. The fabricated bandage is tested in short exercise as well as continued long-term (72 hours) monitoring during normal daily activities. The attained quality of the measured ECG signals is fully satisfactory for rhythm-based cardiac analysis also during moderate-intensity exercise. After pre-processing, the signals could be used also for more profound morphological analysis of ECG wave shapes.acceptedVersionPeer reviewe

A novel technique for analysis of postural information with wearable devices

These days, as many jobs involve sitting behind desks and working with computers for extended periods, more and more people are suffering from back problems. Maintenance of an appropriate posture may prevent future back problems. There are various medical methods for studying postures abnormalities of the back but most of these methods are limited to be utilized in diagnostics and follow-up of treatment and not used in a continuous or in a preventive manner. Therefore, designing and developing methods for measuring, analyzing and reporting of posture information, aimed for prevention of future back problems is of fundamental interest. In this work, a proof-of-concept system, including five accelerometer sensor units is presented. Additionally, an index, which we call spine inclination index (SII), is introduced and used for converting the raw data to meaningful presentable information. Initial evaluation includes measurements with six subjects. Subjects were asked to mimic accentuated kyphotic, straight and accentuated lordotic postures while sitting. Our results show that the designed device and SII index are able to distinguish between different postures very well. In addition, since this device measures the inclination angle of different spinal postures, its output can be directly compared with other widely used methods.acceptedVersionPeer reviewe

Optimal short distance electrode locations for impedance pneumography measurement from the frontal thoracic area

Electrical impedance pneumography signal is a valuable tool in qualifying better the person’s health condition. It can be used in monitoring of respiration rate, rhythm and tidal volume. Impedance pneumography has also the potential in ambulatory physiological monitoring systems that are increasingly often implemented using plaster-like on-body devices. In such cases, the area of electrode substrate may be limited and therefore, the electrode configuration, which is able to provide both a clinically valuable electrocardiogram signal and accurate pulmonary information, is an issue. EAS is a useful small area electrode configuration that can be used for electrocardiogram measurements. In this work, different two-electrode bipolar pairs of EAS system are tested for impedance pneumography measurements. Two additional electrodes are also considered in these tests. Our results show that the electrode pair S-A provides the most accurate respiration cycle length and is least affected by movement artifact. Additionally, the results show that this electrode pair produces the signals with highest amplitude.acceptedVersionPeer reviewe