Gari Clifford
University of Oxford, Engineering Science, Faculty Member
Objective: To develop a robust heart rate (HR) estimation method based on the HR estimates derived from multiple electrocardiogram (ECG) leads from intensive care patients. Methods: Heart rate was obtained by an open source QRS detection... more
Objective: To develop a robust heart rate (HR) estimation method based on the HR estimates derived from multiple electrocardiogram (ECG) leads from intensive care patients. Methods: Heart rate was obtained by an open source QRS detection algorithm. Physiological signal quality indices (SQI) were obtained by analyzing the morphological and statistical characteristics of each waveform and their relationships. Robust HR estimation was obtained by a Kalman filter based upon the SQI adjustment.
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Journal of Critical Care, Volume 28, Issue 1, Pages e20-e21, February 2013, Authors:Alistair EW Johnson; Gari D. Clifford.
Abstract In this work, we describe a beat-by-beat method for assessing the clinical utility of pulsatile waveforms, primarily recorded from cardiovascular blood volume or pressure changes, concentrating on the photoplethysmogram (PPG).... more
Abstract In this work, we describe a beat-by-beat method for assessing the clinical utility of pulsatile waveforms, primarily recorded from cardiovascular blood volume or pressure changes, concentrating on the photoplethysmogram (PPG). Physiological blood flow is nonstationary, with pulses changing in height, width and morphology due to changes in heart rate, cardiac output, sensor type and hardware or software pre-processing requirements.
Abstract The authors have previously described a method for ectopic beat detection in the electrocardiogram using an auto-associative neural network. Here they present a method that utilises principal component analysis to optimise the... more
Abstract The authors have previously described a method for ectopic beat detection in the electrocardiogram using an auto-associative neural network. Here they present a method that utilises principal component analysis to optimise the complexity of the neural network and uses singular value decomposition to determine the initial values for the weights
Here's a cutting-edge, practical book that offers you a thorough understanding of state-of-the-art techniques for electrocardiogram (ECG) data analysis. Placing emphasis on the selection, modeling, classification, and interpretation of... more
Here's a cutting-edge, practical book that offers you a thorough understanding of state-of-the-art techniques for electrocardiogram (ECG) data analysis. Placing emphasis on the selection, modeling, classification, and interpretation of data based on advanced signal processing and artificial intelligence techniques, the book helps you design, implement, and evaluate software systems used for the analysis of ECG and related data.
Results: Processing of the patient's V6 electrode in position (ii) is shown in Fig. 1. ECGreal is extracted from the MHD signal in Fig. 1 (b) with the ST segment preserved. In Fig. 1 (c), the MHD voltage exhibits maximal amplitude during... more
Results: Processing of the patient's V6 electrode in position (ii) is shown in Fig. 1. ECGreal is extracted from the MHD signal in Fig. 1 (b) with the ST segment preserved. In Fig. 1 (c), the MHD voltage exhibits maximal amplitude during the ST segment. Oscillating positive and negative MHD voltages during systole can be explained by flow vortices during the cardiac cycle. In Fig.
This focus issue of Physiological Measurement follows the 38th Annual International Computing in Cardiology (CinC) Conference, hosted in Hangzhou, China in September 2011 by Zhejiang University. Each year, the NIH-sponsored PhysioNet... more
This focus issue of Physiological Measurement follows the 38th Annual International Computing in Cardiology (CinC) Conference, hosted in Hangzhou, China in September 2011 by Zhejiang University. Each year, the NIH-sponsored PhysioNet resource (http://physionet.
American Journal of Obstetrics & Gynecology, Volume 204, Issue 1, Pages S256, January 2011, Authors:Caitlin McDonnell; Gari Clifford; Reza Sameni; Jay Ward; Jim Robertson; Adam Wolfberg.
A method for processing cardiac signals includes accepting, from a sensor system, a set of one or more signals, the signals including components of a desired cardiac signal and components of a substantially periodic interfering signal.... more
A method for processing cardiac signals includes accepting, from a sensor system, a set of one or more signals, the signals including components of a desired cardiac signal and components of a substantially periodic interfering signal. The method is applicable for extraction of desired fetal cardiac signals from signals with interference from the maternal cardiac signal.
Objectives. To develop a computerized algorithm to quantify fetal heart rate (FHR) variability and compare it to perinatologists' interpretation of FHR variability. Methods. FHR variability was calculated using data from 30 women who had... more
Objectives. To develop a computerized algorithm to quantify fetal heart rate (FHR) variability and compare it to perinatologists' interpretation of FHR variability. Methods. FHR variability was calculated using data from 30 women who had a fetal scalp electrode placed for a clinical indication, and compared to the assessment of FHR variability from four perinatologists who interpreted paper tracings of the same data. Inter-rater reliability was calculated and receiver-operator curve analysis was done. Results.
Background High fidelity 12-lead ECG is important for physiological monitoring during cardiovascular interventions. A dominant ECG R-wave is essential for synchronizing cardiac MRI. Obtaining the real ECG in MRI is challenging due to a... more
Background High fidelity 12-lead ECG is important for physiological monitoring during cardiovascular interventions. A dominant ECG R-wave is essential for synchronizing cardiac MRI. Obtaining the real ECG in MRI is challenging due to a superimposed Magneto-Hydro-Dynamic (MHD) voltage (VMHD)[1], & strong induced voltages from MRI switched gradients. Detecting acute ischemia by ST segment [2] is difficult due to VMHD peaks that occur during this period.
Abstract A completely automated algorithm to detect poor-quality electrocardiograms (ECGs) is described. The algorithm is based on both novel and previously published signal quality metrics, originally designed for intensive care... more
Abstract A completely automated algorithm to detect poor-quality electrocardiograms (ECGs) is described. The algorithm is based on both novel and previously published signal quality metrics, originally designed for intensive care monitoring. The algorithms have been adapted for use on short (5–10 s) single-and multi-lead ECGs. The metrics quantify spectral energy distribution, higher order moments and inter-channel and inter-algorithm agreement.
Abstract Patients with obstructive sleep apnea (OSA) syndrome experience repeated periods of apnea and arousal during sleep. A condition which in short term leads to excessive daytime sleepiness and in the long term may have clinical... more
Abstract Patients with obstructive sleep apnea (OSA) syndrome experience repeated periods of apnea and arousal during sleep. A condition which in short term leads to excessive daytime sleepiness and in the long term may have clinical consequences such as stroke and cardiovascular abnormalities. Although complex equipment can be used to screen for sleep apnea, the screening tests are often expensive, inconvenient for the patient, and time-consuming to be manually analysed.
Many resource-poor communities across the globe lack access to quality healthcare, due to shortages in medical expertise and poor availability of medical diagnostic devices. In recent years, mobile phones have become increasingly complex... more
Many resource-poor communities across the globe lack access to quality healthcare, due to shortages in medical expertise and poor availability of medical diagnostic devices. In recent years, mobile phones have become increasingly complex and ubiquitous. These devices present a tremendous opportunity to provide low-cost diagnostics to under-served populations and to connect non-experts with experts.
Abstract An automated algorithm to assess electrocardiogram (ECG) quality for both normal and abnormal rhythms is presented for false arrhythmia alarm suppression of intensive care unit (ICU) monitors. A particular focus is given to the... more
Abstract An automated algorithm to assess electrocardiogram (ECG) quality for both normal and abnormal rhythms is presented for false arrhythmia alarm suppression of intensive care unit (ICU) monitors. A particular focus is given to the quality assessment of a wide variety of arrhythmias. Data from three databases were used: the Physionet Challenge 2011 dataset, the MIT-BIH arrhythmia database, and the MIMIC II database.
Abstract: A device and process for the collection and analysis of physiological data includes obtaining physiological data concerning at least one subject from at least one sensor, transmitting the physiological data to a centralized... more
Abstract: A device and process for the collection and analysis of physiological data includes obtaining physiological data concerning at least one subject from at least one sensor, transmitting the physiological data to a centralized location, and streaming the physiological data from the central location to at ieast two remote locations, and analyzing the physiological data with at least one algorithm during, prior to, and/or subsequent to the one or more of the obtaining, streaming, and analyzing steps.
A method, system, and computer readable medium executable on a computer for at least one of filtering, segmenting, compressing and classifying an ECG or similar signal includes the steps of fitting a nonlinear signal model to the signal... more
A method, system, and computer readable medium executable on a computer for at least one of filtering, segmenting, compressing and classifying an ECG or similar signal includes the steps of fitting a nonlinear signal model to the signal using an optimization algorithm, such as nonlinear least squares, and determining features in the nonlinear signal model.
QoS-constrained policy has an advantage to guarantee QoS requirements requested by users. Quorum systems can ensure the consistency and availability of replicated data despite the benign failure of data repositories. We propose a Quorum... more
QoS-constrained policy has an advantage to guarantee QoS requirements requested by users. Quorum systems can ensure the consistency and availability of replicated data despite the benign failure of data repositories. We propose a Quorum based resource management scheme, which resource Quorum includes middleware entity and network entity, both can satisfy requirements of application QoS.
Abstract Intensive care unit (ICU) monitors generate a high rate of false alarms when physiological signals are severely corrupted by noise. To suppress the false life-threatening heart rate (HR)-related electrocardiogram arrhythmia... more
Abstract Intensive care unit (ICU) monitors generate a high rate of false alarms when physiological signals are severely corrupted by noise. To suppress the false life-threatening heart rate (HR)-related electrocardiogram arrhythmia alarms, data derived from arterial blood pressure (ABP) signal were used. A new ABP signal quality index (SQI) was designed based upon the combination of two previously reported signal quality measures.
Abstract We present generalizations of our previously published artificial models for generating multi-channel ECG so that the simulation of abnormal rhythms is possible. Using a three-dimensional vectorcardiogram (VCG) formulation, we... more
Abstract We present generalizations of our previously published artificial models for generating multi-channel ECG so that the simulation of abnormal rhythms is possible. Using a three-dimensional vectorcardiogram (VCG) formulation, we generate the normal cardiac dipole for a patient using a sum of Gaussian kernels, fitted to real VCG recordings. Abnormal beats are then specified either as new dipoles, or as perturbations of the existing dipole.
Background Due to the Magneto-Hydro-Dynamic (MHD) effect, blood flow within the MRI's magnetic field (B 0) produces a large voltage during the ST cardiac segment [1]. The peak MHD voltage (V MHD) can be comparable, in higher-field MRIs,... more
Background Due to the Magneto-Hydro-Dynamic (MHD) effect, blood flow within the MRI's magnetic field (B 0) produces a large voltage during the ST cardiac segment [1]. The peak MHD voltage (V MHD) can be comparable, in higher-field MRIs, to the R-wave amplitude of the real Electrocardiogram (ECG real), so that V MHD reduces ECG-gating reliability and prevents ischemia-monitoring during cardiac imaging/interventions.
ABSTRACT Accurate performance metrics for removing noise from the electrocardiogram (ECG) are difficult to define due to the inherently complicated nature of the noise and the absence of knowledge about the underlying dynamical processes.... more
ABSTRACT Accurate performance metrics for removing noise from the electrocardiogram (ECG) are difficult to define due to the inherently complicated nature of the noise and the absence of knowledge about the underlying dynamical processes. By using a previously published model for generating realistic artificial ECG signals and adding both stochastic and deterministic noise, a method for assessing the performance of noise reduction techniques is presented.
Objective We sought to evaluate the accuracy of a novel system for measuring fetal heart rate (FHR) and ST-segment changes using noninvasive electrodes on the maternal abdomen. Study Design Fetal electrocardiograms were recorded using... more
Objective We sought to evaluate the accuracy of a novel system for measuring fetal heart rate (FHR) and ST-segment changes using noninvasive electrodes on the maternal abdomen. Study Design Fetal electrocardiograms were recorded using abdominal sensors from 32 term laboring women who had a fetal scalp electrode (FSE) placed for a clinical indication. Results Good-quality data for FHR estimation were available in 91.2% of the FSE segments and 89.9% of the abdominal electrode segments.