References of "Desaive, Thomas"
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See detailAnalysis of Aortic Energetics from Pulse Wave Examination in a Porcine Study of Septic Shock
Revie, JA; Stevenson, D; Chase, JG et al

in Prceedings of BMS 2012 (2012)

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See detailObservation of incretin effects during enteral feed transitions of critically ill patients
Jamaludin, U. K.; Docherty, P. D.; Geoffrey Chase, J. et al

in e-SPEN Journal (2012), 7(4), 154-159

Background & aims: Critically ill patients are regularly feed via constant enteral (EN) nutrition infusions. However, the incretin effect or its impact on endogenous insulin concentration remains unclear ... [more ▼]

Background & aims: Critically ill patients are regularly feed via constant enteral (EN) nutrition infusions. However, the incretin effect or its impact on endogenous insulin concentration remains unclear. This study determines whether there is an EN-driven incretin effect in critically ill patients requiring glycaemic control. Methods: Clinically validated, model-based time-variant insulin sensitivity (S I) profiles were identified for 52 non-diabetic patients on Specialized Relative Insulin Nutrition Titration (SPRINT) glycaemic control during transitions off EN (ON/OFF), and back on to EN (OFF/ON). Incretin effects were observable via increased modelled S I after the OFF/ON transition or a decreased S I after the ON/OFF transition. Results: Patients exhibited a median -36% (IQR -82% to 24% p = 0.001) reduction after the ON/OFF feed transition, and a median of +32% (IQR -5% to 53%, p = 0.05) rise in measured S I after the OFF/ON transition. However, 32% of patients exhibited increased S I at the OFF/ON transition, and 37% exhibited reduced S I at the ON/OFF transition. The results are likely due to changes in patient condition over the 5-8 h considered outweighing this effect. Blood glucose was the same during both transitions with median shifts of -2% and -3% after the ON/OFF, and OFF/ON transitions (p > 0.5), respectively. Conclusions: Results imply a significant incretin effect is observed at a cohort level. The impact was stronger for the OFF/ON transition indicating that this effect may be blunted by long-term continuous EN infusions. These results provide the data to design conclusive studies, and to inform glycaemic control protocol development and implementation. © 2012 European Society for Clinical Nutrition and Metabolism. [less ▲]

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See detailSTAR Development and Protocol Comparison
Fisk, Liam M.; Le Compte, Aaron J.; Shaw, Geoffrey M. et al

in IEEE Transactions on Biomedical Engineering (2012)

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See detailAlgorithmic Processing of Pressure Waveforms to FacilitateEstimation of Cardiac Elastance
Stevenson, D.; Revie, J.; Chase, J. G. et al

in BioMedical Engineering OnLine (2012), 11

Introduction: Cardiac elastances are highly invasive to measure directly, but are clinically useful due tothe amount of information embedded in them. Information about the cardiac elastance, which can be ... [more ▼]

Introduction: Cardiac elastances are highly invasive to measure directly, but are clinically useful due tothe amount of information embedded in them. Information about the cardiac elastance, which can be used toestimate it, can be found in the downstream pressure waveforms of aortic pressure (Pao) and the pulmonaryartery (Ppa). However these pressure waveforms are typically noisy and biased, and require processing in orderto locate the specific information required for the cardiac elastance estimation. This paper presents the methodto algorithmically process the pressure waveforms. Methods: A shear transform is developed in order to helplocate information in the pressure waveforms. This transform turns difficult to locate corners into easy to locatemaximum or minimum points as well as providing error correction. Results: The method located all points 87out of 88 waveforms for Ppa to within the sampling frequency. For Pao, out of 616 total points, 605 were foundwithin 1%, 5 within 5%, 4 within 10% and 2 within 20%. Conclusions: The presented method provides arobust, accurate and dysfunction independent way to locate points on the aortic and pulmonary artery pressurewaveforms, allowing the non-invasive estimation of the left and right cardiac elastance. [less ▲]

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See detailBeat-to-beat estimation of the continuous left and right cardiac elastance from metrics commonly available in clinical settings.
Stevenson, David; Revie, James; Chase, J. Geoffrey et al

in BioMedical Engineering OnLine (2012), 11(1), 73

ABSTRACT: INTRODUCTION: : Functional time-varying cardiac elastances (FTVE) contain a rich amount of information about the specific cardiac state of a patient. However, a FTVE waveform is very invasive to ... [more ▼]

ABSTRACT: INTRODUCTION: : Functional time-varying cardiac elastances (FTVE) contain a rich amount of information about the specific cardiac state of a patient. However, a FTVE waveform is very invasive to directly measure, and is thus currently not used in clinical practice. This paper presents a method for the estimation of a patient specific FTVE, using only metrics that are currently available in a clinical setting. METHOD: : Correlations are defined between invasively measured FTVE waveforms and the aortic and pulmonary artery pressures from 2 cohorts of porcine subjects, 1 induced with pulmonary embolism, the other with septic shock. These correlations are then used to estimate the FTVE waveform based on the individual aortic and pulmonary artery pressure waveforms, using the "other" dysfunction's correlations as a cross validation. RESULTS: : The cross validation resulted in 1.26% and 2.51% median errors for the left and right FTVE respectively on pulmonary embolism, while the septic shock cohort had 2.54% and 2.90% median errors. CONCLUSIONS: : The presented method accurately and reliably estimated a patient specific FTVE, with no added risk to the patient. The cross validation shows that the method is not dependent on dysfunction and thus has the potential for generalisation beyond pulmonary embolism and septic shock. [less ▲]

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See detailModèle unidimensionnel instationnaire de l'activité pacemaker cardiaque induite par le feedback mécano-électrique dans un environnement thermo-électro-mécanique
Collet, Arnaud ULg; Desaive, Thomas ULg; Dauby, Pierre ULg

in Annales de Cardiologie et d'Angeiologie (2012)

Aim of the study: In a healthy heart, the mechano-electric feedback (MEF) process acts as an intrinsic regulatory mechanism of the myocardium which allows the normal cardiac contraction by damping ... [more ▼]

Aim of the study: In a healthy heart, the mechano-electric feedback (MEF) process acts as an intrinsic regulatory mechanism of the myocardium which allows the normal cardiac contraction by damping mechanical perturbations in order to generate a new healthy electromechanical situation. However, under certain conditions, the MEF can be a generator of dramatic arrhythmias by inducing local electrical depolarizations as a result of abnormal cardiac tissue deformations, via stretch-activated channels (SACs). Then, these perturbations can propagate in the whole heart and lead to global cardiac dysfunctions. In the present study, we qualitatively investigate the influence of temperature on autonomous electrical activity generated by the MEF. Method: We introduce a one-dimensional time-dependent model containing all the key ingredients that allow accounting for the excitation-contraction coupling, the MEF and the thermoelectric coupling. Results: Our simulations show that an autonomous electrical activity can be induced by cardiac deformations, but only inside a certain temperature interval. In addition, in some cases, the autonomous electrical activity takes place in a periodic way like a pacemaker. We also highlight that some properties of action potentials, generated by the mechano-electric feedback, are significantly influenced by temperature. Moreover, in the situation where a pacemaker activity occurs, we also show that the period is heavily temperature-dependent. Conclusions: Our qualitative model shows that the temperature is a significant factor with regards to the electromechanical behavior of the heart and more specifically, with regards to the autonomous electrical activity induced by the cardiac tissue deformations. [less ▲]

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See detailInterface Design and Human Factors Consideration for Model-Based Tight Glycemic Control in Critical Care
Ward, Logan; Steel, James; Le Compte, Aaron et al

in Journal of Diabetes Science and Technology (2012)

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See detailStochastic Targeted (STAR) Glycemic Control - Design, Safety and Performance
Evans, Alicia; Le Compte, Aaron; Tan, Chian-Siong et al

in Journal of Diabetes Science and Technology (2012)

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See detailData Entry Errors and Design for Model-Based Tight Glycemic Control in Critical Care
Ward, Logan; Steel, James; Le Compte, Aaron et al

in Journal of Diabetes Science and Technology (2012)

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See detailParameter Identification in a Model of the Cardiovascular System Including the Atria
Pironet, Antoine ULg; Revie, James A.; Paeme, Sabine ULg et al

in 10th Belgian Day on Biomedical Engineering (2011, December 02)

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See detailEffects of temperature on pacemaker activity induced by mechano-electric feedback in a one-dimensional model of a ring-shaped cardiac fiber
Collet, Arnaud ULg; Desaive, Thomas ULg; Dauby, Pierre ULg

in NCBME (Ed.) 10th Belgian Day on Biomedical Engineering (2011, December 02)

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See detailParameter Identification in a Model of the Cardiovascular System Including the Atria
Pironet, Antoine ULg; Revie, James A.; Paeme, Sabine ULg et al

Poster (2011, December 02)

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See detailStructural model of the mitral valve included in a cardiovascular closed loop model
Paeme, Sabine ULg; Moorhead, Kate; Chase, J. Geoffrey et al

Poster (2011, December)

A minimal cardiovascular system (CVS) model including mitral valve dynamics has been previously validated in silico. However parameters of this model are difficult to link with structural and anatomical ... [more ▼]

A minimal cardiovascular system (CVS) model including mitral valve dynamics has been previously validated in silico. However parameters of this model are difficult to link with structural and anatomical components of the valve. This research describes the integration of a structural model of the mitral valve in an existing closed-loop cardiovascular system (CVS) model [less ▲]

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See detailGlycemic Variability, Hypoglycemia and Organ Failure in the Glucontrol Study
Penning, Sophie ULg; Le Compte, Aaron J.; Preiser, Jean-Charles et al

Poster (2011, December)

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See detailMathematical multi-scale model of the cardiovascular system including mitral valve dynamics. Application to ischemic mitral insufficiency
Paeme, Sabine ULg; Moorhead, Katherine; Chase, J. Geoffrey et al

in BioMedical Engineering OnLine (2011), 10(1), 86

Valve dysfunction is a common cardiovascular pathology. Despite significant clinical research, there is little formal study of how valve dysfunction affects overall circulatory dynamics. Validated models ... [more ▼]

Valve dysfunction is a common cardiovascular pathology. Despite significant clinical research, there is little formal study of how valve dysfunction affects overall circulatory dynamics. Validated models would offer the ability to better understand these dynamics and thus optimize diagnosis, as well as surgical and other interventions. A cardiovascular and circulatory system (CVS) model has already been validated in silico, and in several animal model studies. It accounts for valve dynamics using Heaviside functions to simulate a physiologically accurate “open on pressure, close on flow” law. However, it does not consider real-time valve opening dynamics and therefore does not fully capture valve dysfunction, particularly where the dysfunction involves partial closure. This research describes an updated version of this previous closed-loop CVS model that includes the progressive opening of the mitral valve, and is defined over the full cardiac cycle. Simulations of the cardiovascular system with healthy mitral valve are performed, and, the global hemodynamic behaviour is studied compared with previously validated results. The error between resulting pressure-volume (PV) loops of already validated CVS model and the new CVS model that includes the progressive opening of the mitral valve is assessed and remains within typical measurement error and variability. Simulations of ischemic mitral insufficiency are also performed. Pressure-Volume loops, transmitral flow evolution and mitral valve aperture area evolution follow reported measurements in shape, amplitude and trends. The resulting cardiovascular system model including mitral valve dynamics provides a foundation for clinical validation and the study of valvular dysfunction in vivo. The overall models and results could readily be generalised to other cardiac valves. [less ▲]

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See detailInfluence of thermoelectric coupling on pacemaker activity generated by mechano-electric feedback in a one-dimensional ring-shaped model of cardiac fiber
Collet, Arnaud ULg; Desaive, Thomas ULg; Pierard, Luc ULg et al

in XXIIIrd congress of the International Society of Biomechanics, July 3-7, 2011 (2011, July 05)

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See detailInfluence of thermoelectric coupling on pacemaker activity generated by mechano-electric feedback in a one-dimensional ring-shaped model of cardiac fiber
Collet, Arnaud ULg; Desaive, Thomas ULg; Pierard, Luc ULg et al

Poster (2011, July 05)

Recently, the influence of thermal processes on electrophysiology has clearly been underlined, using a FitzHugh–Nagumo-type (FHN-type) model. When the temperature is raised, the action potential duration ... [more ▼]

Recently, the influence of thermal processes on electrophysiology has clearly been underlined, using a FitzHugh–Nagumo-type (FHN-type) model. When the temperature is raised, the action potential duration (APD) has been shown to shorten, while the action potential (AP) amplitude decreases, and the conduction velocity increases. In the present study, we investigate the effects of thermoelectric coupling on mechano-electric feedback (MEF), and more specifically, on pacemaker activity generated by MEF. To investigate these effects, thermoelectric coupling is introduced in a one-dimensional ring-shaped electromechanical model of cardiac fiber, which takes into account excitation-contraction coupling (ECC), as well as MEF. [less ▲]

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