A Wearable Device For Physical and Emotional Health Monitoring

Personal health monitoring systems are emerging as promising solutions to develop ultra-small, portable devices that can continuously monitor and process several vital body parameters. In this work, we present a wearable device for physical and emotional health monitoring. The device obtains user’s key physiological signals: ECG, respiration, Impedance Cardiogram (ICG), blood pressure and skin conductance and derives the user’s emotion states as well. We have developed embedded algorithms that process the bio-signals in real-time to detect any abnormalities (cardiac arrhythmias and morphology changes) in the ECG and to detect key parameters (such as the Pre- Ejection Period and fluid status level) from the ICG. We present a novel method to detect continuous beat-by-beat blood pressure from the ECG and ICG signals, as well as a realtime embedded emotion classifier that computes the emotion levels of the user. Emotions are classified according to their attractiveness (positive valence) or their averseness (negative valence) in the horizontal valence dimension. The excitement level induced by the emotions is represented by high to low positions in the vertical arousal dimension of the valence-arousal space. The signals are measured either intermittently by touching the metal electrodes on the device (for point-of-care testing) or continuously, using a chest strap for long term monitoring. The processed data from device is sent to a mobile phone using a Bluetooth Low Energy protocol. Our results show that the device can monitor the signals continuously, providing accurate detection of the motion state, for over 72 hours on a single battery charge

Enabling Wearable Hemodynamic Monitoring Using Multimodal Cardiomechanical Sensing Systems

Hemodynamic parameters such as blood pressure and stroke volume are instrumental to understanding the pathogenesis of cardiovascular disease. Unfortunately, the monitoring of these hemodynamic parameters is still limited to in-clinic measurements and cumbersome hardware precludes convenient, ubiquitous use. To address this burden, in this work, we explore seismocardiogram-based wearable multimodal sensing techniques to estimate blood pressure and stroke volume. First, the performance of a multimodal, wrist-worn device capable of obtaining noninvasive pulse transit time measurements is used to estimate blood pressure in an unsupervised, at-home setting. Second, the feasibility of this wrist-worn device is comprehensively evaluated in a diverse and medically underserved population over the course of several perturbations used to modulate blood pressure through different pathways. Finally, the ability of wearable signals—acquired from a custom chest-worn biosensor—to noninvasively quantify stroke volume in patients with congenital heart disease is examined in a hospital setting. Collectively, this work demonstrates the advancements necessary towards enabling noninvasive, longitudinal, and accurate measurements of these hemodynamic parameters in remote settings, which offers to improve health equity and disease monitoring in low-resource settings.Ph.D

Dynamic relationship between cardiac imaging and physiological measurements

PhD ThesisImpedance cardiography (ICG) is a non-invasive technique to measure the dynamic changes in electrical impedance of the thorax. Photoplethymgraphy (PPG) is an optical- based non-invasive physiological measurement technique used to detect the blood volume pulses in the microvascular bed of tissue. These two physiological measurements have potential clinical importance to enable simple and cost-efficient ways to examine cardiovascular function and provide surrogate or additional clinical information to the measures from cardiac imaging. However, because the origins of the characteristic waveforms of the impedance and pulse are still not well understood, the clinical applications of these two techniques are limited. There were two main aims in this study: 1) to obtain a better understanding of the origins of the pulsatile impedance changes and peripheral pulse by linking their characteristic features beat-by-beat to those from simultaneous echocardiograms; 2) to validate the clinical indices from ICG and PPG with those well-established echocardiographic indices. Physiological signals, including ECGs, impedance, the first derivative impedance and finger and ear pulses, were simultaneously recorded with echocardiograms from 30 male healthy subjects at rest. The timing sequence of cardiovascular events in a single cardiac cycle was reconstructed with the feature times obtained from the physiological measurements and images. The relations of the time features from the impedance with corresponding features from images and pulses were investigated. The relations of the time features from peripheral pulses with corresponding features from images were also investigated. Furthermore, clinical time indices measured from the impedance and pulse were validated with the reference to the echocardiograms. Finally, the effects of age, heart rate and blood pressure on the image and physiological measurements were examined. According to the reconstructed timing sequence, it was evident that the systolic waves of the thoracic impedance and peripheral pulse occurred following left ventricular ejection. The impedance started to fall 26 ms and the pulse arrived at the fingertip 162 ms after the aortic valve opened. A diastolic wave was observed during the ventricular passive filling phase on the impedance and pulse. The impedance started to recover during the late ventricular ejection phase when the peripheral pulse was rising up. While the pulsatile impedance changes were mainly correlated with valve movement, the derivative impedance (velocity of impedance change) was more correlated with aortic flow (velocity of blood 2 flow). The foot of the finger pulse was significantly correlated with aortic valve open (R = 0.361, P < 0.05), while its systolic peak was strongly correlated with the aortic valve 2 closing (R = 0.579, P < 0.001). Although the pulse had similar waveform shapes to the inverted impedance waveform, the associations between the time features of these two signals were weak. During the validation of potential clinical indices from ICG, significant correlation was found between the overall duration of the derivative impedance systolic wave (359 ms) and the left ventricular ejection time (LVET) measured by aortic valve open duration from M- 2 mode images (329 ms) (R = 0.324, P < 0.001). The overall duration from the finger pulse foot to notch (348 ms) was also significantly correlated with the LVET from M-mode 2 images (R = 0.461, P < 0.001). Therefore, both ICG and PPG had the potential to provide surrogates to the LVET measurement. Age influenced the cardiovascular diastolic function more than systolic function on normal subjects. With age increasing, the reduction of the left ventricular passive filling was compensated by active filling. The ratio of the passive filling duration to the active 2 filling duration decreased with age (R = 0.143, P < 0.05). The influence of age on the diastolic wave of the impedance signals was striking. The impedance diastolic wave disappeared gradually with age. The effects of age on the peripheral pulse were mainly on the shortened pulse foot transit time (PPT) and prolonged pulse rise time. The large artery f stiffness index (SI) increased with age. Most time intervals were prolonged with heart rate slowing down. The effects of systolic blood pressure were evident on pulse transit time and pulse diastolic rising time. Driven by higher systolic blood pressure, both PPT and rising f time decreased significantly (P < 0.001). In conclusion, from the analysis based on simultaneous physiological measurements and echocardiograms, both the pulsatile impedance changes and peripheral volume pulse were initiated by left ventricular ejection. The thoracic impedance changes reflected volume changes in the central great vessels, while the first derivative impedance was associated with the velocity of blood flow. Both ICG and PPG had the potential to provide surrogates for the measures of cardiac mechanical functions from images. The PPG technique also enabled the assessment of changes in vascular function caused by age.Institute of Cellular Medicine Newcastle Universit

Aerospace medicine and biology: A continuing bibliography with indexes, supplement 183

This bibliography lists 273 reports, articles, and other documents introduced into the NASA scientific and technical information system in July 1978

Aerospace Medicine and Biology: A continuing bibliography with indexes, supplement 171

This bibliography lists 186 reports, articles, and other documents introduced into the NASA scientific and technical information system in August 1977

A cumulative index to the 1976 issues of a continuing bibliography on Aerospace Medicine and Biology

This publication is a cumulative index to the abstracts contained in Supplements 151 through 162 of Aerospace Medicine and Biology: A continuing bibliography. It includes three indexes - subject, personal author, and corporate source

Evidence of left ventricular wall movement actively decelerting aortic

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.Efficient function of the left ventricle (LV) is achieved by coherent behaviour of its circumferential and longitudinal myocardial components. Little was known about the direct association between the long and minor axis velocities and the overall haemodynamics generated by ventricular systolic function such as aortic waves. The forward running expansion wave (FEW) during late systole contains important information about the condition of the LV and its interaction with the arterial system. The aim of this thesis was to underpin the mechanics and timing of the LV wall velocities, which are associated with the deceleration of flow. Both invasive and noninvasive data have been analysed in canines and humans and the following conclusions can be drawn. LV long axis peak shortening velocity lags consistently behind the minor axis, representing a degree of normal asynchrony. The FEW is seen to have a slow onset before a rapid increase in energy. The slow onset corresponds with the time that the long axis reaches its peak velocity of shortening. After both axes reach their respective maximum shortening velocity they continue to contract, although at a slow steady velocity until late ejection when there is a sudden simultaneous change of shortening velocity of both axes. This time corresponds with peak aortic pressure and the rapid increase in energy of the FEW. The time that the minor axis reaches its maximum velocity of shortening interestingly coincides with the arrival of the reflected wave at the LV during mid-systole. During canine aortic manipulation through the introduction of total occlusions along the aorta, the sequence of events observed in control conditions remains unchanged. In humans both LV wall movement and carotid wave intensity can be measured successfully using non-invasive methods. The FEW is generated when the last long axis segment begins to slow. The minor axis begins to slow before this time and corresponds to the time of peak aortic flow

Aerospace medicine and biology: A cumulative index to the continuing bibliography of the 1973 issues

A cumulative index to the abstracts contained in Supplements 112 through 123 of Aerospace Medicine and Biology A Continuing Bibliography is presented. It includes three indexes: subject, personal author, and corporate source