Showing papers by "Nigel H. Lovell published in 2016"

Wearable pendant device monitoring using new wavelet-based methods shows daily life and laboratory gaits are different.

Abstract: Morbidity and falls are problematic for older people. Wearable devices are increasingly used to monitor daily activities. However, sensors often require rigid attachment to specific locations and shuffling or quiet standing may be confused with walking. Furthermore, it is unclear whether clinical gait assessments are correlated with how older people usually walk during daily life. Wavelet transformations of accelerometer and barometer data from a pendant device worn inside or outside clothing were used to identify walking (excluding shuffling or standing) by 51 older people (83 ± 4 years) during 25 min of 'free-living' activities. Accuracy was validated against annotated video. Training and testing were separated. Activities were only loosely structured including noisy data preceding pendant wearing. An electronic walkway was used for laboratory comparisons. Walking was classified (accuracy ≥97 %) with low false-positive errors (≤1.9%, κ ≥ 0.90). Median free-living cadence was lower than laboratory-assessed cadence (101 vs. 110 steps/min, p < 0.001) but correlated (r = 0.69). Free-living step time variability was significantly higher and uncorrelated with laboratory-assessed variability unless detrended. Remote gait impairment monitoring using wearable devices is feasible providing new ways to investigate morbidity and falls risk. Laboratory-assessed gait performances are correlated with free-living walks, but likely reflect the individual's 'best' performance.

QRS Detection Algorithm for Telehealth Electrocardiogram Recordings

Abstract: Objective: QRS detection algorithms are needed to analyze electrocardiogram (ECG) recordings generated in telehealth environments. However, the numerous published QRS detectors focus on clean clinical data. Here, a “UNSW” QRS detection algorithm is described that is suitable for clinical ECG and also poorer quality telehealth ECG. Methods: The UNSW algorithm generates a feature signal containing information about ECG amplitude and derivative, which is filtered according to its frequency content and an adaptive threshold is applied. The algorithm was tested on clinical and telehealth ECG and the QRS detection performance is compared to the Pan–Tompkins (PT) and Gutierrez–Rivas (GR) algorithm. Results: For the MIT-BIH Arrhythmia database (virtually artifact free, clinical ECG), the overall sensitivity ( Se ) and positive predictivity (+ P ) of the UNSW algorithm was >99%, which was comparable to PT and GR. When applied to the MIT-BIH noise stress test database (clinical ECG with added calibrated noise) after artifact masking, all three algorithms had overall Se >99%, and the UNSW algorithm had higher + P (98%, p Se and 95% + P which was superior to PT (+ P : p Se and + P : p Conclusion: This is the first study to describe a QRS detection algorithm for telehealth data and evaluate it on clinical and telehealth ECG with superior results to published algorithms. Significance: The UNSW algorithm could be used to manage increasing telehealth ECG analysis workloads.

Quaternion-Based Complementary Filter for Attitude Determination of a Smartphone

Abstract: A geometrically intuitive quaternion-based complementary filter has been developed, which estimates the attitude of a smartphone using signals obtained from the device’s internal magnetic and inertial measurement unit. This method introduces two correction factors $\mu _{_{a}}$ , which governs the rate at which the accelerometer corrects the pitch/roll angle, and $\mu _{_{m}}$ , which controls the rate at which the yaw angle is corrected by the magnetometer. The smartphone’s attitude can be determined by combining information from the tri-axial gyroscope (measures the rate at which the device rotates), the tri-axial accelerometer (measures the acceleration due to gravity in the absence of body movement), and the tri-axial magnetometer (can be used to determine the direction of geomagnetic north). In order to validate the algorithm, a non-ferrous rectangular plate with retroreflective markers affixed at each corner was attached to the smartphone enabling its attitude to be tracked by an optical motion capture system. The accuracy of the algorithm ( $\phi _{_{\text {RMSE}}} = 3.37 ^{\circ}$ , $\theta _{_{\text {RMSE}}} = 1.84 ^{\circ}$ , $\psi _{_{\text {RMSE}}} = 4.83 ^{\circ}$ ) was assessed as ten subjects performed five normal daily activities while the smartphone was loosely fixed to the upper thigh to simulate being carried in a pants pocket. The optimal tuning parameters ( $\mu _{_{a}}=0.003$ and $\mu _{_{m}}=0.001$ ) for the algorithm across all the body movements were also identified.

Low-Power Fall Detector Using Triaxial Accelerometry and Barometric Pressure Sensing

Abstract: Falls are the number one cause of injuries in the elderly. A wearable fall detector can automatically detect the occurrence of a fall and alert a caregiver or a medical rescue group for immediate assistance, mitigating fall-related injuries. However, most studies on fall detection to date have focused on the accuracy of detection while neglecting power efficiency and battery life, and hence the developed fall detectors usually cannot operate for a long period (a year or more) without recharging or replacing their batteries. This paper presents a low-power fall detector that utilizes triaxial accelerometry and barometric pressure sensing. This fall detector reduces its power consumption through both hardware- and firmware-based approaches. This study also incorporates several human trials to develop and evaluate the device, including simulated falls and activities of daily living. A benchtop power measurement test is also conducted to estimate the battery life with data from a one-week free-living trial. These experiments show that the fall detector achieves high sensitivity (97.5% and 93.0%) and specificity (93.2% and 87.3%) on training and testing datasets, while providing an estimated battery life of 664.9 days.

Unintended Consequences of Wearable Sensor Use in Healthcare. Contribution of the IMIA Wearable Sensors in Healthcare WG.

Abstract: Objectives: As wearable sensors take the consumer market by storm, and medical device manufacturers move to make their devices wireless and appropriate for ambulatory use, this revolution brings with it some unintended consequences, which we aim to discuss in this paper. Methods: We discuss some important unintended consequences, both beneficial and unwanted, which relate to: modifications of behavior; creation and use of big data sets; new security vulnerabilities; and unforeseen challenges faced by regulatory authorities, struggling to keep pace with recent innovations. Where possible, we proposed potential solutions to unwanted consequences. Results: Intelligent and inclusive design processes may mitigate unintended modifications in behavior. For big data, legislating access to and use of these data will be a legal and political challenge in the years ahead, as we trade the health benefits of wearable sensors against the risk to our privacy. The wireless and personal nature of wearable sensors also exposes them to a number of unique security vulnerabilities. Regulation plays an important role in managing these security risks, but also has the dual responsibility of ensuring that wearable devices are fit for purpose. However, the burden of validating the function and security of medical devices is becoming infeasible for regulators, given the many software apps and wearable sensors entering the market each year, which are only a subset of an even larger ‘internet of things’. Conclusion: Wearable sensors may serve to improve wellbeing, but we must be vigilant against the occurrence of unintended consequences. With collaboration between device manufacturers, regulators, and end-users, we balance the risk of unintended consequences occurring against the incredible benefit that wearable sensors promise to bring to the world.

Health-Enabling and Ambient Assistive Technologies: Past, Present, Future

Abstract: Background: During the last decades, health-enabling and ambient assistive technologies became of considerable relevance for new informatics-based forms of diagnosis, prevention, and therapy. Objectives: To describe the state of the art of health-enabling and ambient assistive technologies in 1992 and today, and its evolution over the last 25 years as well as to project where the field is expected to be in the next 25 years. In the context of this review, we define health-enabling and ambient assistive technologies as ambiently used sensor-based information and communication technologies, aiming at contributing to a person's health and health care as well as to her or his quality of life. Methods: Systematic review of all original articles with research focus in all volumes of the IMIA Yearbook of Medical Informatics. Surveying authors independently on key projects and visions as well as on their lessons learned in the context of health-enabling and ambient assistive technologies and summarizing their answers. Surveying authors independently on their expectations for the future and summarizing their answers. Results: IMIA Yearbook papers containing statements on health-enabling and ambient assistive technologies appear first in 2002. These papers form a minor part of published research articles in medical informatics. However, during recent years the number of articles published has increased significantly. Key projects were identified. There was a clear progress on the use of technologies. However proof of diagnostic relevance and therapeutic efficacy remains still limited. Reforming health care processes and focussing more on patient needs are required. Conclusions: Health-enabling and ambient assistive technologies remain an important field for future health care and for interdisciplinary research. More and more publications assume that a person's home and their interaction therein, are becoming important components in health care provision, assessment, and management.

Vision function testing for a suprachoroidal retinal prosthesis: effects of image filtering

Abstract: Objective One strategy to improve the effectiveness of prosthetic vision devices is to process incoming images to ensure that key information can be perceived by the user. This paper presents the first comprehensive results of vision function testing for a suprachoroidal retinal prosthetic device utilizing of 20 stimulating electrodes. Further, we investigate whether using image filtering can improve results on a light localization task for implanted participants compared to minimal vision processing. No controlled implanted participant studies have yet investigated whether vision processing methods that are not task-specific can lead to improved results. Approach Three participants with profound vision loss from retinitis pigmentosa were implanted with a suprachoroidal retinal prosthesis. All three completed multiple trials of a light localization test, and one participant completed multiple trials of acuity tests. The visual representations used were: Lanczos2 (a high quality Nyquist bandlimited downsampling filter); minimal vision processing (MVP); wide view regional averaging filtering (WV); scrambled; and, system off. Main results Using Lanczos2, all three participants successfully completed a light localization task and obtained a significantly higher percentage of correct responses than using MVP ([Formula: see text]) or with system off ([Formula: see text]). Further, in a preliminary result using Lanczos2, one participant successfully completed grating acuity and Landolt C tasks, and showed significantly better performance ([Formula: see text]) compared to WV, scrambled and system off on the grating acuity task. Significance Participants successfully completed vision tasks using a 20 electrode suprachoroidal retinal prosthesis. Vision processing with a Nyquist bandlimited image filter has shown an advantage for a light localization task. This result suggests that this and targeted, more advanced vision processing schemes may become important components of retinal prostheses to enhance performance. ClinicalTrials.gov Identifier: NCT01503576.

The Effect of Electric Cross-Talk in Retinal Neurostimulation.

Abstract: PURPOSE: To investigate the efficacy of electric field shaping in modulating the extent and activation threshold in retinal neurostimulation. This study aims to quantify the interference of neighboring stimulation sites by assessing the shift in the activation threshold produced by a concomitant interfering stimulus. METHODS: Electrical stimuli were applied to healthy retinae in a feline model (n = 4) using a 24-channel electrode array surgically implanted in the suprachoroidal space. A 96-channel penetrating electrode array was used for recording cortical responses to a number of stimulation paradigms. Data were analyzed offline. Concurrent monopolar and hexapolar stimuli were delivered at primary and interfering sites separated by up to 2.19 mm to evaluate electric cross-talk. The spike rate was fit to a sigmoidal curve to estimate the P50 threshold. The slope of the linear regression of the P50 value versus interfering current level was considered as a measure of cross-talk. RESULTS: Concurrent monopolar stimulation produced a proportional drop in the P50 of approximately 20% of the interfering current level in presence of a primary monopolar and hexapolar stimulus. On the other hand, hexapolar interference did not alter activation thresholds at the primary site. CONCLUSIONS: Hexapolar stimulation reduces electric cross-talk between neighboring sites and represents a technique to reduce interference between individual stimulation sites. In contrast, concurrent monopolar stimulation produces a reduction of the activation threshold of stimuli delivered nearby. Thus, a single source of subthreshold monopolar charge injection can provide benefit in the form of significant threshold reduction simultaneously at multiple stimulation sites.

Electrical activity of ON and OFF retinal ganglion cells: a modelling study

Abstract: Objective Retinal ganglion cells (RGCs) demonstrate a large range of variation in their ionic channel properties and morphologies. Cell-specific properties are responsible for the unique way RGCs process synaptic inputs, as well as artificial electrical signals such as that from a visual prosthesis. A cell-specific computational modelling approach allows us to examine the functional significance of regional membrane channel expression and cell morphology. Approach In this study, an existing RGC ionic model was extended by including a hyperpolarization activated non-selective cationic current as well as a T-type calcium current identified in recent experimental findings. Biophysically-defined model parameters were simultaneously optimized against multiple experimental recordings from ON and OFF RGCs. Main results With well-defined cell-specific model parameters and the incorporation of detailed cell morphologies, these models were able to closely reconstruct and predict ON and OFF RGC response properties recorded experimentally. Significance The resulting models were used to study the contribution of different ion channel properties and spatial structure of neurons to RGC activation. The techniques of this study are generally applicable to other excitable cell models, increasing the utility of theoretical models in accurately predicting the response of real biological neurons.

A Six-Step Framework on Biomedical Signal Analysis for Tackling Noncommunicable Diseases: Current and Future Perspectives

Abstract: Low- and middle-income countries (LMICs) continue to face major challenges in providing high-quality and universally accessible health care Researchers, policy makers, donors, and program implementers consistently strive to develop and provide innovative approaches to eliminate geographical and financial barriers to health care access Recently, interest has increased in using mobile health (mHealth) as a potential solution to overcome barriers to improving health care in LMICs Moreover, with use increasing and cost decreasing for mobile phones and Internet, mHealth solutions are becoming considerably more promising and efficient As part of mHealth solutions, biomedical signals collection and processing may play a major role in improving global health care Information extracted from biomedical signals might increase diagnostic precision while augmenting the robustness of health care workers’ clinical decision making This paper presents a high-level framework using biomedical signal processing (BSP) for tackling diagnosis of noncommunicable diseases, especially in LMICs Researchers can consider each of these elements during the research and design of BSP-based devices, enabling them to elevate their work to a level that extends beyond the scope of a particular application and use This paper includes technical examples to emphasize the applicability of the proposed framework, which is relevant to a wide variety of stakeholders, including researchers, policy makers, clinicians, computer scientists, and engineers [JMIR Biomed Eng 2016;1(1):e1]

Discussion of “the new role of biomedical informatics in the age of digital medicine”

Abstract: This article is part of a For-Discussion-Section of Methods of Information in Medicine about the paper "The New Role of Biomedical Informatics in the Age of Digital Medicine" written by Fernando J. Martin-Sanchez and Guillermo H. Lopez-Campos [1]. It is introduced by an editorial. This article contains the combined commentaries invited to independently comment on the paper of Martin-Sanchez and Lopez-Campos. In subsequent issues the discussion can continue through letters to the editor.

Numerical Simulation of a Biventricular Assist Device with Fixed Right Outflow Cannula Banding During Pulmonary Hypertension

Abstract: As a left ventricular assist device is designed to pump against the systemic vascular resistance (SVR), pulmonary congestion may occur when using such device for right ventricular support. The present study evaluates the efficacy of using a fixed right outflow banding in patients receiving biventricular assist device support under various circulatory conditions, including variations in the SVR, pulmonary vascular resistance (PVR), total blood volume (BV), as well as ventricular contractility. Effect of speed variation on the hemodynamics was also evaluated at varying degrees of PVR. Pulmonary congestion was observed at high SVR and BV. A reduction in right ventricular assist device (RVAD) speed was required to restore pulmonary pressures. Meanwhile, at a high PVR, the risk of ventricular suction was prevalent during systemic hypotension due to low SVR and BV. This could be compensated by increasing RVAD speed. Isolated right heart recovery may aggravate pulmonary congestion, as the failing left ventricle cannot accommodate the resultant increase in the right-sided flow. Compared to partial assistance, the sensitivity of the hemodynamics to changes in VAD speed increased during full assistance. In conclusion, our results demonstrated that the introduction of a banding graft with a 5 mm diameter guaranteed sufficient reserve of the pump speed spectrum for the regulation of acceptable hemodynamics over different clinical scenarios, except under critical conditions where drug administration or volume management is required.

Restoration of eye closure in facial paralysis using implantable electromagnetic actuator.

Abstract: The most devastating outcome of facial nerve paralysis is the inability to completely close the eye as it can lead to corneal ulceration and loss of vision. Gravity-assisted eye closure with upper lid loading is commonly used; however it is limited in replicating physiological eye closure to adequately lubricate the cornea. Superior results can be obtained using more advanced reconstructive approaches, however they depend on nerve regrowth which may be unpredictable and prolonged. This report describes a novel technique for creating an active eye closure using an implantable actuator. A generated magnetic field creates lateral movement in an electromagnet that is translated to the eyelid through a sling design. The device is powered wirelessly through a transcutaneous induction link and can be hermetically encapsulated for patient safety. The initial phase of device development is presented including data of a fully functioning prototype and the results of its application in animal and human cadavers.

Bio-Inspired PVDF-Based, Mouse Whisker Mimicking, Tactile Sensor

Abstract: The design and fabrication of a Polyvinylidene fluoride (PVDF) based, mouse (or rodent) whisker mimicking, tactile sensor is presented. Unlike previous designs reported in the literature, this sensor mimics the mouse whisker not only mechanically, but it also makes macro movements just like a real mouse whisker in a natural environment. We have developed a mathematical model and performed finite element analysis using COMSOL, in order to optimise the whisker to have the same natural frequency as that of a biological whisker. Similarly, we have developed a control system that enables the whisker mimicking sensor to vibrate at variable frequencies and conducted practical experiments to validate the response of the sensor. The natural frequency of the whisker can be designed anywhere between 35 and 110 Hz, the same as a biological whisker, by choosing different materials and physical dimensions. The control system of this sensor enables the whisker to vibrate between 5 and 236 Hz.

Assistive peripheral phosphene arrays deliver advantages in obstacle avoidance in simulated end-stage retinitis pigmentosa: a virtual-reality study.

Abstract: Objective The prospective efficacy of peripheral retinal prostheses for guiding orientation and mobility in the absence of residual vision, as compared to an implant for the central visual field (VF), was evaluated using simulated prosthetic vision (SPV). Approach Sighted volunteers wearing a head-mounted display performed an obstacle circumvention task under SPV. Mobility and orientation performance with three layouts of prosthetic vision were compared: peripheral prosthetic vision of higher visual acuity (VA) but limited VF, of wider VF but limited VA, as well as centrally restricted prosthetic vision. Learning curves using these layouts were compared fitting an exponential model to the mobility and orientation measures. Main results Using peripheral layouts, performance was superior to the central layout. Walking speed with both higher-acuity and wider-angle layouts was 5.6% higher, and mobility errors reduced by 46.4% and 48.6%, respectively, as compared to the central layout. The wider-angle layout yielded the least number of collisions, 63% less than the higher-acuity and 73% less than the central layout. Using peripheral layouts, the number of visual-scanning related head movements was 54.3% (higher-acuity) and 60.7% (wider-angle) lower, as compared to the central layout, and the ratio of time standing versus time walking was 51.9% and 61.5% lower, respectively. Learning curves did not differ between layouts, except for time standing versus time walking, where both peripheral layouts achieved significantly lower asymptotic values compared to the central layout. Significance Beyond complementing residual vision for an improved performance, peripheral prosthetic vision can effectively guide mobility in the later stages of retinitis pigmentosa (RP) without residual vision. Further, the temporal dynamics of learning peripheral and central prosthetic vision are similar. Therefore, development of a peripheral retinal prosthesis and early implantation to alleviate VF constriction in RP should be considered to extend the target group and the time of benefit for potential retinal prosthesis implantees.

Cortical responses following simultaneous and sequential retinal neurostimulation with different return configurations

Abstract: Researchers continue to develop visual prostheses towards safer and more efficacious systems. However limitations still exist in the number of stimulating channels that can be integrated. Therefore there is a need for spatial and time multiplexing techniques to provide improved performance of the current technology. In particular, bright and high-contrast visual scenes may require simultaneous activation of several electrodes. In this research, a 24-electrode array was suprachoroidally implanted in three normally-sighted cats. Multi-unit activity was recorded from the primary visual cortex. Four stimulation strategies were contrasted to provide activation of seven electrodes arranged hexagonally: simultaneous monopolar, sequential monopolar, sequential bipolar and hexapolar. Both monopolar configurations showed similar cortical activation maps. Hexapolar and sequential bipolar configurations activated a lower number of cortical channels. Overall, the return configuration played a more relevant role in cortical activation than time multiplexing and thus, rapid sequential stimulation may assist in reducing the number of channels required to activate large retinal areas.

A 4+1 architecture for in vivo electrophysiology visual prosthesis

Abstract: Researchers around the globe are working towards restoring vision to the blind through the development of a visual neuroprosthesis. Overcoming physical, technical and biological limitations represents one of the main challenges for the scientific community and will eventually benefit the wellbeing of the recipients of these devices. Thus, understanding the physiological mechanisms of prosthetic vision plays a key role. In this context, in vivo electrophysiological studies are aiming to shed light on new stimulation paradigms that can potentially lead to improved visual perception. This paper describes a multi-viewpoint architecture of an experimental setup for the investigation of electrically evoked potentials in a retinal neuroprosthesis.

Mapping of bionic array electric field focusing in plasmid DNA-based gene electrotransfer.

Abstract: Molecular medicine through gene therapy is challenged to achieve targeted action. This is now possible utilizing bionic electrode arrays for focal delivery of naked (plasmid) DNA via gene electrotransfer. Here, we establish the properties of array-based electroporation affecting targeted gene delivery. An array with eight 300 μm platinum ring electrodes configured as a cochlear implant bionic interface was used to transduce HEK293 cell monolayers with a plasmid-DNA green fluorescent protein (GFP) reporter gene construct. Electroporation parameters were pulse intensity, number, duration, separation and electrode configuration. The latter determined the shape of the electric fields, which were mapped using a voltage probe. Electrode array-based electroporation was found to require ~100 × lower applied voltages for cell transduction than conventional electroporation. This was found to be due to compression of the field lines orthogonal to the array. A circular area of GFP-positive cells was created when the electrodes were ganged together as four adjacent anodes and four cathodes, whereas alternating electrode polarity created a linear area of GFP-positive cells. The refinement of gene delivery parameters was validated in vivo in the guinea pig cochlea. These findings have significant clinical ramifications, where spatiotemporal control of gene expression can be predicted by manipulation of the electric field via current steering at a cellular level.

A simplified state-space model of biventricular assist device-cardiovascular system interaction

Abstract: A simplified state-space model of biventricular assist device (BiVAD)-cardiovascular system (CVS) interaction is presented. The state-space equations includes a six-compartments CVS model incorporating the ventricles, the pulmonary and systemic circulations as well as the non-linear behavior of the valve flow, together with a left ventricular assist device (LVAD) and a right ventricular assist device (RVAD) component. The left and right pump speeds serve as the input variables for the state-space model. The model is simulated with three operational modes, i.e. (i) RVAD speed < LVAD speed, (ii) same LVAD and RVAD speeds and (iii) inclusion of a 6 mm restriction at the right outflow cannula. The effect of RVAD speed variation on the steady state hemodynamics is also studied with and without an outflow banding restriction. Our simulated results are validated with experimental data obtained from clinical, in vivo and in vitro studies provided in the literatures. We observed that despite its simplicity, the model is able to reproduce the observed trends in the reported studies, thus making it feasible for the development of robust yet practical control algorithms.

Low-power operation of a barometric pressure sensor for use in an automatic fall detector

Abstract: The use of a barometric pressure sensor in a wearable fall detector has been shown to improve the detection accuracy by determining the altitude change associated with the fall event. However, the barometer is a high-power-consuming sensor. This paper proposes a fall detection approach using a hermetically sealed and waterproof enclosure incorporating a small window covered by a semi-permeable membrane (SPM) to delay the equilibrium of internal and external pressures. This feature can be utilized to limit the time the barometer is powered but still capturing critical pressure information to discriminate fall and non-fall events. The proposed fall detection system is evaluated with an existing data set of simulated fall and activities of daily living in which the barometric pressure data are delayed using a mathematical model of the enclosure and SPM assembly. Also, a benchtop test is performed to estimate the power and battery life. The proposed fall detection system achieves 94.0% sensitivity and 90.0% specificity with an estimated battery life of 995.7 days.

Local Heterogeneous Electrical Restitution Properties of Rabbit Atria

Abstract: INTRODUCTION This study aims to characterize the regional variability in rate-adaptation in the atria. METHODS AND RESULTS Action potential (AP) responses to pulses with uniform as well as pseudo-random non-uniform pacing intervals were recorded from rabbit sino-atrial node, right and left atrial pectinate as well as pulmonary vein antrum tissue preparations using conventional intracellular glass microelectrodes. Steady-state restitution curves were reconstructed for various AP waveform metrics. We observed significant variability between the four regions under basal pacing representing the rabbit resting heart rate as well as regional variability in rate-adaptation to increased pacing frequencies. Right-left atrial restitution differences were further confirmed using the non-uniform pacing protocol, with significant differences in AP amplitude, duration (APD) as well as maximum phase 0 depolarization rate restitution curves in response to an identical sequence of non-uniform pacing intervals. In addition, we report regional differences in alternans of AP waveform metrics, over a wide range of pacing frequencies and not simply prior to 1:1 entrainment being lost. We also observed an increase in APD90 along the conduction pathway from the left atrium to pulmonary vein junction. CONCLUSIONS Our results identified significant regional differences in electrical restitution in the rabbit atria and suggest their dependency on both baseline AP morphology and local intrinsic differences in rate-adaptation. We propose that the atrial heterogeneity in rate-adaptation could contribute to arrhythmogenesis and the greater susceptibility of pulmonary vein myocardial sleeves to ectopic foci and reentrant activity.

Electroporation system for controlled localized therapeutics delivery

Abstract: Embodiments of the present invention provide an electroporation system comprising an electroporation probe having at least two contiguous electrodes configured to be inserted into biological tissue for electroporation treatment, and a pulse generator electrically connected to the probe and configured to drive the electroporation probe using a sequence of one or more electric pulses to cause current transmission through the probe and induce a non-uniform electric field in the biological tissue proximate the probe electrodes. Treatment tissue can be targeted by controlling the probe configuration, carrier solution characteristics and parameters of the electroporation pulse sequence to achieve predictable electroporation outcomes. This electroporation control method can also reduce potentially toxic effects of electroporation treatment.

Modeling the Debye dielectric response in the time domain for a liquid crystal-based biopotential optrode

Abstract: Multielectrode arrays (MEAs) are widely used for recording biopotentials, with an ongoing research effort to improve their characteristics and performance. In this spirit, we are currently investigating a novel concept for a liquid crystal-based optical electrode (optrode) that has the potential to overcome some of the limitations of MEAs, including that of wiring complexity. In this paper we present a model to fully describe the electrical response of the proposed optrode to biopotentials, taking into account dielectric relaxation. Since the frequency dependence of the complex permittivity is difficult to specify in time-stepped finite element (FE) simulations, where the implementation of time-convolution is nontrivial, we adopt an alternative approach to dielectric relaxation via the polarization vector. This approach, which is based on the Debye model, is then implemented in a FE model of the optrode. We show that the dielectric response of the liquid crystal layer has an effect on the complex signal behavior of the sensed biopotentials that must be taken into account when modeling the optrode.

A Kalman filter to estimate altitude change during a fall

Abstract: Barometers have been incorporated into fall detectors in order to enhance the accuracy of fall detection algorithms, however they are power-hungry devices. We present an offline evaluation of a Kalman filter (KF) for estimating the pressure change during a fall that enables low-power operation of the barometer. The KF takes advantage of the fact that a semi-permeable air membrane on a waterproof fall detector enclosure causes a delay in the equilibrium between internal and external enclosure pressure, and this delay enables the barometer to be switched off until a free-fall is detected. We assessed the KF using data obtained from simulated falls and activities of daily living. The KF was able to differentiate between fall and non-fall activities, with the average measured pressure change during a fall of 8 Pa best determined using a delay in pressure equalization of 20 seconds. The KF detected a change in altitude faster than a simple moving average filter (MAF), reaching 66% of its final value before the MAF was able to initialize.

Computational modeling of a novel liquid crystal-based optrode

Abstract: Multielectrode arrays are a powerful tool for recording biopotentials, however they are limited by issues related to wiring complexity and channel-count. We present a novel concept for a liquid crystal-based optical electrode (optrode) that does not require the electrical circuitry associated with reading and amplifying each channel, thus providing superior spatial resolution and signal-to-noise ratio. Through computational modeling, we show that it is possible to accurately image biopotentials by coupling them to the electrodes of a LC cell and measuring their re ectance under parallel polarisers.

Understanding the cochlear implant environment by mapping perilymph proteomes from different species

Abstract: Cochlear implants operate within a bony channel of the cochlea, bathed in a fluid known as the perilymph. The perilymph is a complex fluid containing ions and proteins, which are known to actively interact with metallic electrodes. To improve our understanding of how cochlear implant performance varies in preclinical in vivo studies in comparison to human trials and patient outcomes, the protein composition (or perilymph proteome) is needed. Samples of perilymph were gathered from feline and guinea pig subjects and analyzed using liquid chromatography with tandem mass spectrometry (LC-MS/MS) to produce proteomes and compare against the recently published human proteome. Over 64% of the proteins in the guinea pig proteome were found to be common to the human proteome. The proportions of apolipoproteins, enzymes and immunoglobulins showed little variation between the two proteomes, with other classes showing similarity. This establishes a good basis for comparison of results. The results for the feline profile showed less similarity with the human proteome and would not provide a quality comparison. This work highlights the suitability of the guinea pig to model the biological environment of the human cochlear and the need to carefully select models of the biological environment of a cochlear implant to more adequately translate in vitro and in vivo studies to the clinic.

Simulation of motor current waveforms in monitoring aortic valve state during ventricular assist device support

Abstract: Monitoring of aortic valve (AV) opening and closure during left ventricular assist device (LVAD) heart pump support is crucial in preventing AV abnormalities and remodeling caused by anomalous resirculation. In this study, simulations of LVAD motor current waveforms were undertaken to investigate AV response to rotary blood pump assistance, as well as to detect AV open and close status under heart failure conditions. A two-dimensional fluid-structure interaction finite-element model is presented to predict AV state during LVAD outflow. The data will be useful in the development of a pump speed controller for optimal management of pump outflow.

Classification of Implantable Rotary Blood Pump States With Class Noise

Abstract: A medical case study related to implantable rotary blood pumps is examined. Five classifiers and two ensemble classifiers are applied to process the signals collected from the pumps for the identification of the aortic valve nonopening pump state. In addition to the noise-free datasets, up to $40\%$ class noise has been added to the signals to evaluate the classification performance when mislabeling is present in the classifier training set. In order to ensure a reliable diagnostic model for the identification of the pump states, classifications performed with and without class noise are evaluated. The multilayer perceptron emerged as the best performing classifier for pump state detection due to its high accuracy as well as robustness against class noise.