Cardiac period responses after cessation of vagai stimulation were analyzed in the cat and the dog using non-linear curve fittting techniques. The relative undershoot (post vagai tachycardia) was investigated before and after muscarinic blockade with atropine. It was found that after atropine the tachycardia was abolished in the cat but persisted in the dog. However the altered temporal dynamics to that pre-atropine indicated that this tachycardia had a different etiology to that before blockade. It is hypothesized that this tachycardia is due to co-release of vasoactive intestinal polypeptide (VIP) from vagai nerve terminals.
Features were developed which accounted for the changing orientation of the inertial measurement unit (IMU) relative to the body, and demonstrably improved the performance of models for human activity recognition (HAR). The method is proficient at separating periods of standing and sedentary activity (i.e., sitting and/or lying) using only one IMU, even if it is arbitrarily oriented or subsequently re-oriented relative to the body; since the body is upright during walking, learning the IMU orientation during walking provides a reference orientation against which sitting and/or lying can be inferred. Thus, the two activities can be identified (irrespective of the cohort) by analyzing the magnitude of the angle of shortest rotation which would be required to bring the upright direction into coincidence with the average orientation from the most recent 2.5 s of IMU data. Models for HAR were trained using data obtained from a cohort of 37 older adults (83.9 ± 3.4 years) or 20 younger adults (21.9 ± 1.7 years). Test data were generated from the training data by virtually re-orienting the IMU so that it is representative of carrying the phone in five different orientations (relative to the thigh). The overall performance of the model for HAR was consistent whether the model was trained with the data from the younger cohort, and tested with the data from the older cohort after it had been virtually re-oriented (Cohen's Kappa 95% confidence interval [0.782, 0.793]; total class sensitivity 95% confidence interval [84.9%, 85.6%]), or the reciprocal scenario in which the model was trained with the data from the older cohort, and tested with the data from the younger cohort after it had been virtually re-oriented (Cohen's Kappa 95% confidence interval [0.765, 0.784]; total class sensitivity 95% confidence interval [82.3%, 83.7%]).
With the increasing shift in the population profile to the older demographic and rising healthcare costs, it is more critical for developed countries to deliver long-term and financially sustainable healthcare services, especially in the area of residential aged care. A consensus exists that innovations in the area of Wireless Sensor Networks (WSNs) are key enabling technologies for reaching this goal. The major focus of this article is WSN design considerations for ubiquitous wellness monitoring systems in residential aged care facilities. Major enabling technologies for building a pervasive WSN will be detailed, including descriptions on sensor design, wireless communication protocols and network topologies. Also examined are data processing methods and knowledge management tools to support the collection of sensor data and their subsequent analysis for health assessment. To introduce future healthcare reform in residential aged care, two aspects of wellness monitoring, vital signs and activities of daily living (ADL) monitoring, will be discussed.
Abstract Despite the rapid advancement of left ventricular assist devices (LVADs), adverse events leading to deaths have been frequently reported in patients implanted with LVADs, including bleeding, infection, thromboembolism, neurological dysfunction and hemolysis. Cannulation forms an important component with regards to thrombus formation in assisted patients by varying the intraventricular flow distribution in the left ventricle (LV). To investigate the correlation between LVAD cannula placement and potential for thrombus formation, detailed analysis of the intraventricular flow field was carried out in the present study using a two way fluid structure interaction (FSI), axisymmetric model of a passive LV incorporating an inflow cannula. Three different cannula placements were simulated, with device insertion near the LV apex, penetrating one-fourth and mid-way into the LV long axis. The risk of thrombus formation is assessed by analyzing the intraventricular vorticity distribution and its associated vortex intensity, amount of stagnation flow in the ventricle as well as the level of wall shear stress. Our results show that the one-fourth placement of the cannula into the LV achieves the best performance in reducing the risk of thrombus formation. Compared to cannula placement near the apex, higher vortex intensity is achieved at the one-fourth placement, thus increasing wash out of platelets at the ventricular wall. One-fourth LV penetration produced negligible stagnation flow region near the apical wall region, helping to reduce platelet deposition on the surface of the cannula and the ventricular wall.
We propose dynamical models for pulsatile flow and head estimation in an implantable rotary blood pump. Pulsatile flow and head data were obtained using a circulatory mock loop where fluid solutions with different values of viscosities were used as a blood analogue with varying haematocrit (HCT). Noninvasive measurements of power and pump speed were used with HCT values as inputs to the flow model while the estimated flow was used with the speed as inputs to a head estimation model. Linear regression analysis between estimated and measured flows obtained from a mock loop resulted in a highly significant correlation (R2=0.982) and a mean absolute error (e) of 0.323 L min(-1), while for head, R2=0.933 and e=7.682 mmHg were obtained. R2=0.849 and e=0.584 L min(-1) were obtained when the same model derived in the mock loop was used for flow estimation in ex vivo porcine data (N=6). Furthermore, in the steady state, the solution of the presented flow model can be described by a previously designed and verified static model. The models developed herein will play a vital role in developing a robust control system of the pump flow coping with changing physiological demands.
In order to deliver sufficient phosphene quantities to convey effective vision in a prosthesis device, simultaneous stimuli is necessary. We present in vitro experimental results of the current distribution between stimulation sites during simultaneous stimulation of platinum electrodes immersed in physiological saline. Stimuli were delivered using circuitry that utilizes (a) current source only, (b) current sink only, and (c) the combination of a balanced current source and current sink, to deliver and recover balanced charge at each stimulation site. The results from these experiments support our decision to implement balanced combined current source and current sink circuitry in an application specific integrated circuit (ASIC).
With the increasing shift in the population profile to the older demographic and rising healthcare costs, it is more critical for developed countries to deliver long-term and financially sustainable healthcare services, especially in the area of residential aged care. A consensus exists that innovations in the area of Wireless Sensor Networks (WSNs) are key enabling technologies for reaching this goal. The major focus of this article is WSN design considerations for ubiquitous wellness monitoring systems in residential aged care facilities. Major enabling technologies for building a pervasive WSN will be detailed, including descriptions on sensor design, wireless communication protocols and network topologies. Also examined are data processing methods and knowledge management tools to support the collection of sensor data and their subsequent analysis for health assessment. To introduce future healthcare reform in residential aged care, two aspects of wellness monitoring, vital signs and activities of daily living (ADL) monitoring, will be discussed.
In recent years, extensive studies have been conducted in the area of pumping state detection for implantable rotary blood pumps. However, limited studies have focused on automatically identifying the aortic valve non-opening (ANO) state despite its importance in the development of control algorithms aiming for myocardial recovery. In the present study, we investigated the performance of 14 ANO indices derived from the pump speed waveform using four different types of classifiers, including linear discriminant analysis, logistic regression, back propagation neural network, and k-nearest neighbors (KNN). Experimental measurements from four greyhounds, which take into consideration the variations in cardiac contractility, systemic vascular resistance, and total blood volume were used. By having only two indices, (i) the root mean square value, and (ii) the standard deviation, we were able to achieve an accuracy of 92.8% with the KNN classifier. Further increase of the number of indices to five for the KNN classifier increases the overall accuracy to 94.6%.
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