Master’s dissertation (Dissertations and theses)
Cardio-pulmonary mechanics and minimal modelling in critical care
de Bournonville, Sébastien
2015
 

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Keywords :
Cardio-pulmonary; Cardiovascular modelling
Abstract :
[en] Positive pressure ventilation is a widely used support for patients in intensive care units.Their weak respiratory condition is often accompanied by a weak cardiac status and haemodya-mical instability. This ventilation support has significant impacts on the cardiovascular systemthat are known but not predicted nor taken into account when varying the respiratory para-meters such as the positive end-expiratory pressure. The fact is that positive end-expiratorypressure increases the intrathoracic pressure. Ultimately, this will lead to decreases in cardiacoutput and stroke volume of the left ventricle. The good parametrization of such ventilator istherefore of primary importance for the critically ill patient cares.This master’s thesis seeks to develop a new minimal model of the cardiovascular and therespiratory system that is new in terms of its cardiovascular lumped model representationand the fact that it takes into account the cardiopulmonary interactions. This new model isaimed to be implemented at bedside for real time monitoring of the patients’ cardiac status asfunction of the respiratory inputs. Its ultimate use will be prediction and active control of thisstatus to improve the work of clinicians.The physiological knowledge in terms of cardiopulmonary interactions was investigated toselect the specific behaviour that will be modelled. The mathematical representation of themodel was precisely described and was designed as a function of physiological relevancy, com-putational weight and data availability. These factors lead to the design of a three chambermodel of the cardiovascular system, focused on the left ventricle, the aorta and the vena cavawhich represent the common available data in ICUs. This three chamber model was coupledto a single compartment model of the lung to compute the intrathoracic pressure that actson intrathoracic structures. Porcine measurements performed with the chest closed were usedto build patient specific models by fitting the model outputs to these measurements. Theconstruction of patient specific models was performed by identifying the patient-specific pa-rameter values of the model. For this purpose, the data were first processed to compute andidentify many parameters. Then an iterative optimization process was implemented to fit themodel to the specific datasets.This model was validated against the aforementioned porcine datasets. It showed physiolo-gical behaviours and reactions in a cardiovascular point of view as well as in a cardiopulmonaryinteractions point of view. By analysing the several identified parameters on the PEEP levelof each pigs, correlations between haemodynamical parameters and the PEEP level applied tothe patients were identified. It also allowed the confirmation that linear ESPVR models arenot appropriated for relatively high levels of PEEPs. The model showed the expected beha-viour of decreasing cardiac output for an increasing PEEP although not in the expected ranges.Eventually, this work opens many research hypotheses and questions in this field. Thequestion of implementing the model at bedside for real-time monitoring should be investigated.A modelling of the correlation between haemodynamic parameters and PEEP based on theresult of this work should also be investigated.
Disciplines :
Mechanical engineering
Author, co-author :
de Bournonville, Sébastien ;  Université de Liège - ULiège > 2e an. master ingé. civ. biomédical, fin. appr.
Language :
English
Title :
Cardio-pulmonary mechanics and minimal modelling in critical care
Alternative titles :
[fr] Mécanique cardio-pulmonaire et modélisation minimale en soins intensifs
Defense date :
June 2015
Number of pages :
xiii, 66 + 2
Institution :
ULiège - Université de Liège
Degree :
Master en ingénieur civil biomédical, à finalité approfondie.
Promotor :
Desaive, Thomas
President :
Geris, Liesbet  ;  Université de Liège - ULiège > GIGA > GIGA In silico medecine - Biomechanics Research Unit
Jury member :
Chase, Goeffrey J.
Gilet, Tristan  ;  Université de Liège - ULiège > Aérospatiale et Mécanique (A&M)
Kolh, Philippe  ;  Université de Liège - ULiège > GIGA
Dauby, Pierre  ;  Université de Liège - ULiège > GIGA > GIGA In silico medecine - Thermodynamics of Irreversible Processes
Available on ORBi :
since 03 December 2015

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