Range90 as indicator for ventilator output versus patients demand: NAVA and pressure support for non-invasively ventilated patients

in Proceedings of the World Congress on Medical Physics and Biomedical Engineering 2012 (2012)

Glucose control: How tight? - How modeling could help?

Conference (2012)

Cardiovascular modelling and the Intensive Care Unit clinician

in Proceedings of BMS 2012 (2012)

Analysis of Aortic Energetics from Pulse Wave Examination in a Porcine Study of Septic Shock

in Prceedings of BMS 2012 (2012)

Observation of incretin effects during enteral feed transitions of critically ill patients

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 ▲]

Algorithmic Processing of Pressure Waveforms to FacilitateEstimation of Cardiac Elastance

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 ▲]

Modèle unidimensionnel instationnaire de l'activité pacemaker cardiaque induite par le feedback mécano-électrique dans un environnement thermo-électro-mécanique

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 ▲]

Stochastic Targeted (STAR) Glycemic Control - Design, Safety and Performance

in Journal of Diabetes Science and Technology (2012)

Parameter Identification in a Model of the Cardiovascular System Including the Atria

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

Effects of temperature on pacemaker activity induced by mechano-electric feedback in a one-dimensional model of a ring-shaped cardiac fiber

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