Papers by Lionel Tarassenko
Perception, Dec 1, 1990
Books about dreaming range from the 'how to transform your life in no time at all' variety, throu... more Books about dreaming range from the 'how to transform your life in no time at all' variety, through psychoanalytic interpretation, to modern cognitive theory-usually with very little overlap between them. In this new book, Hunt attempts to span the entire range of ideas in explaining the multiple forms of dream experience. Dream research has arrived at a hiatus, claims Hunt. The previous optimism that REM research would 'explain it all' has given way to a deconstruction of dream psychology in which all the major descriptive, theoretical, and research approaches are equally open to question. Throughout the book he contrasts two main approaches, based on saying 'yes' or 'no' to the central question-do dreams have intrinsic meaning? To put it another way-do symbolic processes operate within the dream (and if so are they verbal, visual, or kinesthetic) or does the dream only seem to afford rich meaning because the inherently disorganised contents are interpreted as a story on waking? The question is important not only for theory but also for the big business of dream interpretation and dream work. 'Semantic froth' is all it is according to those who answer 'no'; such as the 19th-century mechanist Robert. Modern successors include Foulkes and, of course, Crick and Mitchison with their neural net approach. But such repeated denials of meaning imply to Hunt that, even for these researchers, meaning is the fundamental question. Starting from this dichotomy, Hunt goes on to consider cognitive science versus organismicholistic cognition, Freud versus Jung, and representational versus presentational symbolism; the dream as perception or as imagery, the centrality or irrelevance of the REM state and of psychoanalytic theory. It is within this framework that he reviews, though not always in a way that is easy to follow, recent dream research. It is only by interaction and juxtaposition that we can make a science out of dream psychology, he argues. Gradually Hunt elaborates his thesis that there are multiple forms of dream. Of special interest are claims of prophetic or telepathic dreams. Here he does not try to answer the vexed question of whether such things actually occur, but simply bemoans the lack of systematic research to find out. Then there are lucid dreams; those in which you know during the dream that you are dreaming and can even take control of the events. This kind of control is found in many shamanic systems and is also claimed to increase with meditation training. Here, as in other parts of the book, Hunt illustrates the points with his own dream accounts from the dream diary he has kept for many years. A three-dimensional 'dream diamond' is the result of this categorisation. Hunt argues that dream research has by-passed the Linnaean stage and we need to return to it. However, I did not find this diamond, with its dimensions of 'vividness' and 'degree of symbolic differentiation' and its four faces, either very clear or helpful. The book ends with Hunt's 'synesthetic model of becoming aware'. Consciousness emerges top-down in the putting together of information from the various senses, rather than just being a matter of computation. Although Hunt provides an exciting mix of ideas and some useful study of narrative structures and the relevance of imagery and visuospatial aspects of dreams, it is clear that a true synthesis of the 'multiplicity of dreams' is still a long way off.
Detection of apnoeic and breathing activity through pole-zero analysis of the SpO2signal
A new method using autoregressive modelling and pole tracking is proposed to detect cyclical acti... more A new method using autoregressive modelling and pole tracking is proposed to detect cyclical activity within the oxygen saturation signal, SpO2, for subjects with obstructive sleep apnoea (OSA). OSA is a sleep condition whereby the upper airway is obstructed and a cessation in respiration (apnoea) occurs. The three types of detected activity include: apnoea, mix, and normal breathing, where mix, refers to breathing with a low-frequency component. Overall classifications produced by the analysis are in close agreement with expert scoring of the database. Furthermore, the pole-zero analysis method allows, for the first time, the mix sections to be identified automatically.
Cognitive Systems in Touch with the World: Introduction
Cerebral Hemodynamics in the Newborn Studied Continuously by Transcephalic Electrical-Impedance
Pediatric Research, 1984
Vital sign monitoring and data fusion in haemodialysis
Intra-dialytic hypotension (IDH) is the most common complication in haemodialysis (HD) treatment ... more Intra-dialytic hypotension (IDH) is the most common complication in haemodialysis (HD) treatment and has been linked with increased mortality in HD patients. Despite various approaches towards understanding the underlying physiological mechanisms giving rise to IDH, the causes of IDH are poorly understood. Heart Rate Variability (HRV) has previously been suggested as a predictive measure of IDH. In contrast to conventional spectral HRV measures in which the frequency bands are defined by fixed limits, a new spectral measure of HRV is introduced in which the breathing rate is used to identify and measure the physiologically-relevant peaks of the frequency spectrum. The ratio of peaks leading up to the IDH event was assessed as a possible measure for IDH prediction. Changes in the proposed measure correlate well with the magnitude of abrupt changes in blood pressure in patients with autonomic dysfunction, but there is no such correlation in patients without autonomic dysfunction. At present, routine clinical vital sign monitoring beyond simple weight and blood pressure measurements at the start and end of each session has not established itself in clinical practice. To investigate the benefits of continuous vital sign monitoring in HD patients with regard to detecting and predicting IDH, different population-based and patient-specific models of normality were devised and tested on data from an observational study at the Oxford Renal Unit in which vital signs were recorded during HD sessions. Patient-specific models of normality performed better in distinguishing between IDH and non-IDH data, primarily due to the wide range of vital sign data included as part of the training data in the population-based models. Further, a patient-specific data fusion model was constructed using Parzen windows to estimate a probability density function from the training data consisting of vital signs from IDH-free sessions. Although the model was constructed using four vital sign inputs, novelty detection was found to be primarily driven by blood pressure decreases.</p
In the process of completing this research, I have had the benet of many supportive people. Liste... more In the process of completing this research, I have had the benet of many supportive people. Listed here is a severely attenuated set of those whom I would like to thank. For all others, know that I am eternally grateful. Prof. Lionel Tarassenko for being the world's most understanding advisor. Throughout my stay, there was not a single point at which you threw up your hands and gave up on me, which I believe you were totally entitled to. The academic guidance, emotional support and personal advice you gave me are greatly appreciated, and I hope that someday I will be as good a professor for others as you have been for me. Dr. Gari Cliord for all of his assistance and advice. I have been consistently impressed at your kindness and ingenuity, and I hope that I will be working again with you in the near future. The entire BioSignals Processing group at the IBME for making my stay a truly enjoyable one. Special recognition must also be made of Christina and Lei, who suered the worst of research during pregnancy with me. I was happy to nd that Madame Zaritska was wrong by 8 lbs about baby size! Dr. Mic Craig, Dr. George Moody and Dr. Joon Lee of MIT for their support with the MIMIC II database and research in general. My family and friends for their kind support and encouragement throughout my entire life. My mother, Maryam Reitan Ghassemi, is my rock, and this experience was no exception to her general pattern of sweetness. My husband, Eric Munson, has always been the best man for me, and was somehow able to detect when I needed to smile, laugh, cry or yell. My baby, Razi, whose smile means more to me than anything I have written or could ever write.
Accurate assessment of a child's health is critical for appropriate allocation of medical resourc... more Accurate assessment of a child's health is critical for appropriate allocation of medical resources and timely delivery of healthcare in both primary care (GP consultations) and secondary care (ED consultations). Serious illnesses such as meningitis and pneumonia account for 20% of deaths in childhood and require early recognition and treatment in order to maximize the chances of survival of affected children. Due to time constraints, poorly defined normal ranges, difficulty in achieving accurate readings and the difficulties faced by clinicians in interpreting combinations of vital signs, vital signs are rarely measured in primary care and their utility is limited in emergency departments. This thesis aims to develop a monitoring and data fusion system, to be used in both primary care and emergency department settings during the initial assessment of children suspected of having a serious infection. The proposed system relies on the photoplethysmogram (PPG) which is routinely recorded in different clinical settings with a pulse oximeter using a small finger probe. Foremost of all, I would like to thank my supervisor, Lionel Tarassenko, for his invaluable support, guidance and wisdom. I consider myself very lucky to be given the opportunity to work under his supervision. He is a master of what he does, thank you very much. I would also like to thank Susannah Fleming who provided me with valuable support during the initial days of my DPhil when I joined the group and for her contributions to the setting up of the 8-month clinical trial which forms the core of this thesis. I am indebted to our clinical collaborators, Matthew Thompson, David Mant, Ann Van den Bruel and Richard Stevens from the "Department of Public Health and Primary Care, University of Oxford", who provided regular feedback and valuable insight. Acknowledgments are also extended to Monica Lakhanpaul and Roderick Macfaul for providing me access to their datasets used in this thesis. I am extremely grateful to all the staff members and the paediatric nurses at the Paediatric ED, John Radcliffe Hospital, Oxford who contributed to the ED study. I would especially like to thank Sally Beer, Karen Warnes, and Soubera Yousefi for their efforts and patience during the 8-month clinical trial. I am grateful to all the members of the BSP group, especially David Clifton,
medRxiv (Cold Spring Harbor Laboratory), Jun 1, 2021
Respiratory disorders, including apnoea, are common in preterm infants due to their immature resp... more Respiratory disorders, including apnoea, are common in preterm infants due to their immature respiratory control and function compared with term-born infants. However, our inability to accurately measure respiratory rate in hospitalised infants results in unreported episodes of apnoea and an incomplete picture of respiratory dynamics. We develop, validate and use a novel algorithm to identify inter-breath intervals (IBIs) and apnoeas in infants. In 42 infants (a total of 1600 hours of recordings) we assess IBIs from the chest electrical impedance pneumograph using an adaptive amplitude threshold for the detection of individual breaths. The algorithm is refined by comparing its accuracy with clinically-observed breaths and pauses in breathing. We also develop an automated classifier to differentiate periods of true central apnoea from artefactually low amplitude signal. We use this algorithm to explore its ability to identify morphine-induced respiratory depression in 15 infants. Finally, in 22 infants we use the algorithm to investigate whether retinopathy of prematurity (ROP) screening alters the IBI distribution. 88% of the central apnoeas identified using our algorithm were missed in the clinical notes. As expected, morphine caused a shift in the IBI distribution towards longer IBIs, with significant differences in all IBI metrics assessed. Following ROP screening, there was a shift in the IBI distribution with a significant increase in the proportion of pauses in breathing that lasted more than 10 seconds (t-statistic=1.82, p=0.023). This was not reflected by changes in the monitorderived respiratory rate or episodes of apnoea recorded on clinical charts. Better measurement of infant respiratory dynamics is essential to improve care for hospitalised infants. Use of the novel IBI algorithm demonstrates that following ROP screening increased instability in respiratory dynamics can be detected in the absence of clinically-significant apnoeas.
BIOSIGN/spl trade/ : multi-parameter monitoring for early warning of patient deterioration
JMIR Research Protocols, Oct 27, 2021
Cognitive Systems Remember Experience: Introduction
Elsevier eBooks, 2006
Physiological Measurement, Nov 9, 2004
Inter-patient comparisons of cardiovascular metrics indicative of patient health have been shown ... more Inter-patient comparisons of cardiovascular metrics indicative of patient health have been shown to be successful in differentiating patients on a group rather than an individual level. This is in part due to the range of mental (as well as physical) activity-based variations for each patient and the difficulty assessing physical and mental activity during conscious states. In order to provide an objective scale for measuring central nervous system activity during sleep, the heart rate (RR) interval time series is divided into coarse sleep stage segments in which the LF HF -ratio (the relative balance between low and high frequency power) is estimated for age and sex-matched populations of apnoeic and healthy subjects. Activity-based noise is therefore reduced and a more useful comparison of heart rate variability can be made. Additionally, the spectral estimation performances of the FFT and the Lomb-Scargle periodogram (LSP), a Fourier-based technique for unevenly sampled time series are compared. Separation of patients according to condition is shown to be more pronounced when using the LSP than the FFT. Furthermore, separation is found to be most marked in slow wave sleep.
Quantitative analysis of immunological reactions on silicon surfaces by multiple-angle Brewster angle reflectometry
Biomaterials, 1988
An optical biosensing instrument has been developed for the quantitative analysis of immunologica... more An optical biosensing instrument has been developed for the quantitative analysis of immunological reactions on biochemically sensitized surfaces. It is based on the measurement of reflectance changes of polarized laser light incident on high refractive index substrates at angles close to the pseudo-Brewster angle. Multiple-angle Brewster angle reflectometry (MABAR) has been used to investigate the binding of anti-human serum albumin (a-HSA) to human serum albumin (HSA) coated silicon surfaces. The concentration dependence and reaction kinetics of antibody-antigen complex formation have been studied using red and green He-Ne laser light. A significant increase in sensitivity has been observed with green light.
Journal of Medical Internet Research, Mar 7, 2017
Background: Chronic obstructive pulmonary disease (COPD) is a progressive, chronic respiratory di... more Background: Chronic obstructive pulmonary disease (COPD) is a progressive, chronic respiratory disease with a significant socioeconomic burden. Exacerbations, the sudden and sustained worsening of symptoms, can lead to hospitalization and reduce quality of life. Major limitations of previous telemonitoring interventions for COPD include low compliance, lack of consensus on what constitutes an exacerbation, limited numbers of patients, and short monitoring periods. We developed a telemonitoring system based on a digital health platform that was used to collect data from the 1-year EDGE (Self Management and Support Programme) COPD clinical trial aiming at daily monitoring in a heterogeneous group of patients with moderate to severe COPD. The objectives of the study were as follows: first, to develop a systematic and reproducible approach to exacerbation identification and to track the progression of patient condition during remote monitoring; and second, to develop a robust algorithm able to predict COPD exacerbation, based on vital signs acquired from a pulse oximeter. We used data from 110 patients, with a combined monitoring period of more than 35,000 days. We propose a finite-state machine-based approach for modeling COPD exacerbation to gain a deeper insight into COPD patient condition during home monitoring to take account of the time course of symptoms. A robust algorithm based on short-period trend analysis and logistic regression using vital signs derived from a pulse oximeter is also developed to predict exacerbations. On the basis of 27,260 sessions recorded during the clinical trial (average usage of 5.3 times per week for 12 months), there were 361 exacerbation events. There was considerable variation in the length of exacerbation events, with a mean length of 8.8 days. The mean value of oxygen saturation was lower, and both the pulse rate and respiratory rate were higher before an impending exacerbation episode, compared with stable periods. On the basis of the classifier developed in this work, prediction of COPD exacerbation episodes with 60%-80% sensitivity will result in 68%-36% specificity. Conclusions: All 3 vital signs acquired from a pulse oximeter (pulse rate, oxygen saturation, and respiratory rate) are predictive of COPD exacerbation events, with oxygen saturation being the most predictive, followed by respiratory rate and pulse rate. Combination of these vital signs with a robust algorithm based on machine learning leads to further improvement in positive predictive accuracy.
Classifying nocturnal blood pressure patterns using photoplethysmogram features
2022 44th Annual International Conference of the IEEE Engineering in Medicine & Biology Society (EMBC), Jul 11, 2022
decay in (H start Ϫ H t ). However, this "inverted" decay is likely to be due to subtracting H t ... more decay in (H start Ϫ H t ). However, this "inverted" decay is likely to be due to subtracting H t from a constant value. His expression for H t is an absolute A1C value, not a change in A1C. An initial value, G s , has been specified for G t , and hence an initial value is implicit in his calculations. Subtracting H t from a constant would not be expected to give a valid A1C estimate. To verify this conclusion, we simulated a patient with a constant glucose level followed by an exponential decay upon admission to the hospital. During the preadmission time period, the simulated A1C reached a steady state under the constant glucose conditions, which avoided any ambiguity over the initial value (H start ) of A1C. In this simulation, the decay rates of H t then varied in the same way as those for the glucose data, as would be intuitively expected. The use of two initial values by Trevin ˜o, one for H and one for G, appears to have led to the anomalous result previously reported, rather than any inherent defect in the weighted-average relationship proposed by Tahara and Shima.
Telemetric Bluetooth home BP-monitoring in patients with TIA and minor stroke: feasibility and BP control
Cerebrovascular Diseases, 2014
Nephrology Dialysis Transplantation, May 1, 2015
Data fusion for identification of serious illness in children
ABSTRACT
Vital sign monitoring and analysis in acute coronary syndrome patients
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Papers by Lionel Tarassenko