Unique parameter identification for model-based cardiac diagnosis in critical care
; ; Desaive, Thomas et al
in IFAC Proceedings Volumes (IFAC-PapersOnline) (2009), 7(PART 1), 169-174
Lumped parameter approaches for modeling the cardiovascular system typically have many parameters of which many are not identifiable. The conventional approach is to only identify a small subset of ... [more ▼]
Lumped parameter approaches for modeling the cardiovascular system typically have many parameters of which many are not identifiable. The conventional approach is to only identify a small subset of parameters to match measured data, and to set the remaining parameters at population values. These values are often based on animal data or the "average human" response. The problem, is that setting many parameters at nominal fixed values, may introduce dynamics that are not present in a specific patient. As parameter numbers and model complexity increase, more clinical data is required for validation and the model limitations are harder to quantify. This paper considers the modeling and the parameter identification simultaneously, and creates models that are one to one with the measurements. That is, every input parameter into the model is uniquely optimized to capture the clinical data and no parameters are set at population values. The result is a geometrical characterization of a previously developed six chamber heart model, and a completely patient specific approach to cardiac diagnosis in critical care. In addition, simplified sub-structures of the six chamber model are created to provide very fast and accurate parameter identification from arbitrary starting points and with no prior knowledge on the parameters. Furthermore, by utilizing continuous information from the arterial/pulmonary pressure waveforms and the end-diastolic time, it is shown that only the stroke volumes of the ventricles are required for adequate cardiac diagnosis. This reduced data set is more practical for an intensive care unit as the maximum and minimum volumes are no longer needed, which was a requirement in prior work. The simplified models can also act as a bridge to identifying more sophisticated cardiac models, by providing a generating set of waveforms that the complex models can match to. Most importantly, this approach does not have any predefined assumptions on patient dynamics other than the basic model structure, and is thus suitable for improving cardiovascular management in critical care by optimizing therapy for individual patients. © 2009 IFAC. [less ▲]Detailed reference viewed: 13 (1 ULg)
Influence de la largeur des pores des membranes utilisées au cours de l’hémofiltration et du débit d’ultrafiltration sur la clairance plasmatique de l’interleukine 6 dans un modèle porcin de choc septique.
Delanaye, Pierre ; Janssen, Nathalie ; Dogné, Jean-Michel et al
in Réanimation (2009), 18(1), 037Detailed reference viewed: 55 (19 ULg)
Functional connectivity in the default network during resting state is preserved in a vegetative but not in a brain dead patient.
Boly, Mélanie ; Tshibanda, Luaba ; Vanhaudenhuyse, Audrey et al
in Human Brain Mapping (2009), 30(8), 2393-400
Recent studies on spontaneous fluctuations in the functional MRI blood oxygen level-dependent (BOLD) signal in awake healthy subjects showed the presence of coherent fluctuations among functionally ... [more ▼]
Recent studies on spontaneous fluctuations in the functional MRI blood oxygen level-dependent (BOLD) signal in awake healthy subjects showed the presence of coherent fluctuations among functionally defined neuroanatomical networks. However, the functional significance of these spontaneous BOLD fluctuations remains poorly understood. By means of 3 T functional MRI, we demonstrate absent cortico-thalamic BOLD functional connectivity (i.e. between posterior cingulate/precuneal cortex and medial thalamus), but preserved cortico-cortical connectivity within the default network in a case of vegetative state (VS) studied 2.5 years following cardio-respiratory arrest, as documented by extensive behavioral and paraclinical assessments. In the VS patient, as in age-matched controls, anticorrelations could also be observed between posterior cingulate/precuneus and a previously identified task-positive cortical network. Both correlations and anticorrelations were significantly reduced in VS as compared to controls. A similar approach in a brain dead patient did not show any such long-distance functional connectivity. We conclude that some slow coherent BOLD fluctuations previously identified in healthy awake human brain can be found in alive but unaware patients, and are thus unlikely to be uniquely due to ongoing modifications of conscious thoughts. Future studies are needed to give a full characterization of default network connectivity in the VS patients population. [less ▲]Detailed reference viewed: 81 (20 ULg)
Asthme aigu grave: une affection qui demeure redoutable.
D'Orio, Virginie ; Ghuysen, Alexandre ; Lambermont, Bernard
in Revue Médicale de Liège (2009), 64(7-8), 377-81
Severe exacerbations of asthma can be life-threatening if not aggressively treated. Despite the publication of therapeutic guidelines developed by experts in this field and people education programs ... [more ▼]
Severe exacerbations of asthma can be life-threatening if not aggressively treated. Despite the publication of therapeutic guidelines developed by experts in this field and people education programs, early recognition and characterization of patients at risk for fatal asthma remain scarce. We report the case of a young lady suffering from acute exacerbation of asthma responsible for intensive care admission with long term mechanical ventilation due to the lack in initial appropriate care. [less ▲]Detailed reference viewed: 145 (26 ULg)
Mesure du débit de filtration glomérulaire aux soins intensifs basée sur l’iohexol : clairance plasmatique ou urinaire ?
Delanaye, Pierre ; Cavalier, Etienne ; Lambermont, Bernard et al
in Réanimation (2009), 18(1), 112Detailed reference viewed: 119 (15 ULg)
Robust parameter identification for model-based cardiac diagnosis in critical care
; ; Desaive, Thomas et al
in Proceedings of the 6th IFAC Symposium on Modeling and Control in Biomedical Systems (MCBMS09) (2009)Detailed reference viewed: 14 (4 ULg)
Patient specific model of the cardiovascular system during septic shock
Desaive, Thomas ; ; Lambermont, Bernard et al
in Intensive Care Medicine (2009), 35(suppl. 1), 80Detailed reference viewed: 55 (12 ULg)
Model-based therapeutics for the cardiovascular system - a clinical focus
; ; Desaive, Thomas et al
in 6th IFAC Symposium on Modeling and Control in Biomedical Systems (MCBMS09) (2009)Detailed reference viewed: 13 (4 ULg)
Cotrimoxazole induced mixed type II cryoglobulinemia.
Leclercq, Philippe ; Frippiat, Frédéric ; Lambermont, Bernard
in European Journal of Internal Medicine (2008), 19(4),Detailed reference viewed: 34 (8 ULg)
Effective arterial elastance as an index of pulmonary vascular load.
Morimont, Philippe ; Lambermont, Bernard ; Ghuysen, Alexandre et al
in American Journal of Physiology - Heart and Circulatory Physiology (2008), 294(6), 2736-42
The aim of this study was to test whether the simple ratio of right ventricular (RV) end-systolic pressure (Pes) to stroke volume (SV), known as the effective arterial elastance (Ea), provides a valid ... [more ▼]
The aim of this study was to test whether the simple ratio of right ventricular (RV) end-systolic pressure (Pes) to stroke volume (SV), known as the effective arterial elastance (Ea), provides a valid assessment of pulmonary arterial load in case of pulmonary embolism- or endotoxin-induced pulmonary hypertension. Ventricular pressure-volume (PV) data (obtained with conductance catheters) and invasive pulmonary arterial pressure and flow waveforms were simultaneously recorded in two groups of six pure Pietran pigs, submitted either to pulmonary embolism (group A) or endotoxic shock (group B). Measurements were obtained at baseline and each 30 min after injection of autologous blood clots (0.3 g/kg) in the superior vena cava in group A and after endotoxin infusion in group B. Two methods of calculation of pulmonary arterial load were compared. On one hand, Ea provided by using three-element windkessel model (WK) of the pulmonary arterial system [Ea(WK)] was referred to as standard computation. On the other hand, similar to the systemic circulation, Ea was assessed as the ratio of RV Pes to SV [Ea(PV) = Pes/SV]. In both groups, although the correlation between Ea(PV) and Ea(WK) was excellent over a broad range of altered conditions, Ea(PV) systematically overestimated Ea(WK). This offset disappeared when left atrial pressure (Pla) was incorporated into Ea [Ea * (PV) = (Pes - Pla)/SV]. Thus Ea * (PV), defined as the ratio of RV Pes minus Pla to SV, provides a convenient, useful, and simple method to assess the pulmonary arterial load and its impact on the RV function. [less ▲]Detailed reference viewed: 87 (8 ULg)
Comparison of functional residual capacity and static compliance of the respiratory system during a positive end-expiratory pressure (PEEP) ramp procedure in an experimental model of acute respiratory distress syndrome.
Lambermont, Bernard ; Ghuysen, Alexandre ; Janssen, Nathalie et al
in Critical Care (2008), 12(4), 91
INTRODUCTION: Functional residual capacity (FRC) measurement is now available on new ventilators as an automated procedure. We compared FRC, static thoracopulmonary compliance (Crs) and PaO2 evolution in ... [more ▼]
INTRODUCTION: Functional residual capacity (FRC) measurement is now available on new ventilators as an automated procedure. We compared FRC, static thoracopulmonary compliance (Crs) and PaO2 evolution in an experimental model of acute respiratory distress syndrome (ARDS) during a reversed, sequential ramp procedure of positive end-expiratory pressure (PEEP) changes to investigate the potential interest of combined FRC and Crs measurement in such a pathologic state. METHODS: ARDS was induced by oleic acid injection in six anesthetised pigs. FRC and Crs were measured, and arterial blood samples were taken after induction of ARDS during a sequential ramp change of PEEP from 20 cm H2O to 0 cm H2O by steps of 5 cm H2O. RESULTS: ARDS was responsible for significant decreases in FRC, Crs and PaO2 values. During ARDS, 20 cm H2O of PEEP was associated with FRC values that increased from 6.2 +/- 1.3 to 19.7 +/- 2.9 ml/kg and a significant improvement in PaO2. The maximal value of Crs was reached at a PEEP of 15 cm H2O, and the maximal value of FRC at a PEEP of 20 cm H2O. From a PEEP value of 15 to 0 cm H2O, FRC and Crs decreased progressively. CONCLUSION: Our results indicate that combined FRC and Crs measurements may help to identify the optimal level of PEEP. Indeed, by taking into account the value of both parameters during a sequential ramp change of PEEP from 20 cm H2O to 0 cm H2O by steps of 5 cm H2O, the end of overdistension may be identified by an increase in Crs and the start of derecruitment by an abrupt decrease in FRC. [less ▲]Detailed reference viewed: 52 (5 ULg)
Perception of pain in the minimally conscious state with PET activation: an observational study.
Boly, Mélanie ; Faymonville, Marie-Elisabeth ; et al
in Lancet Neurology (2008), 7(11), 1013-20
BACKGROUND: Patients in a minimally conscious state (MCS) show restricted self or environment awareness but are unable to communicate consistently and reliably. Therefore, better understanding of cerebral ... [more ▼]
BACKGROUND: Patients in a minimally conscious state (MCS) show restricted self or environment awareness but are unable to communicate consistently and reliably. Therefore, better understanding of cerebral noxious processing in these patients is of clinical, therapeutic, and ethical relevance. METHODS: We studied brain activation induced by bilateral electrical stimulation of the median nerve in five patients in MCS (aged 18-74 years) compared with 15 controls (19-64 years) and 15 patients (19-75 years) in a persistent vegetative state (PVS) with (15)O-radiolabelled water PET. By way of psychophysiological interaction analysis, we also investigated the functional connectivity of the primary somatosensory cortex (S1) in patients and controls. Patients in MCS were scanned 57 (SD 33) days after admission, and patients in PVS 36 (9) days after admission. Stimulation intensities were 8.6 (SD 6.7) mA in patients in MCS, 7.4 (5.9) mA in controls, and 14.2 (8.7) mA in patients in PVS. Significant results were thresholded at p values of less than 0.05 and corrected for multiple comparisons. FINDINGS: In patients in MCS and in controls, noxious stimulation activated the thalamus, S1, and the secondary somatosensory or insular, frontoparietal, and anterior cingulate cortices (known as the pain matrix). No area was less activated in the patients in MCS than in the controls. All areas of the cortical pain matrix showed greater activation in patients in MCS than in those in PVS. Finally, in contrast with patients in PVS, those in MCS had preserved functional connectivity between S1 and a widespread cortical network that includes the frontoparietal associative cortices. INTERPRETATION: Cerebral correlates of pain processing are found in a similar network in controls and patients in MCS but are much more widespread than in patients in PVS. These findings might be objective evidence of a potential pain perception capacity in patients in MCS, which supports the idea that these patients need analgesic treatment. [less ▲]Detailed reference viewed: 278 (20 ULg)
Le cas clinique du mois. Un cas rare d'épanchement pleural unilatéral: le syndrome d'hyperstimulation des ovaires.
; Bataille, Yoann ; Duysinx, Bernard et al
in Revue Médicale de Liège (2008), 63(7-8), 474-9
Ovarian hyperstimulation syndrome is the most severe iatrogenic complication of fertilization modern methods. This syndrome is characterized by a massive cystic ovarian enlargement associated with an ... [more ▼]
Ovarian hyperstimulation syndrome is the most severe iatrogenic complication of fertilization modern methods. This syndrome is characterized by a massive cystic ovarian enlargement associated with an acute body fluid shift. Ascite is the most frequent manifestation of this syndrome. In some rare cases ovarian hyperstimulation syndrome is complicated by massive unilateral pleural effusion without ascite. We describe the case of a 36 year old woman who developed a massive unilateral pleural effusion without ascite. An ovarian hyperstimulation syndrome was diagnosed. Chest tube drainage improved patient parameters and symptoms. We discuss the diagnostic approach of pleural effusions. [less ▲]Detailed reference viewed: 104 (5 ULg)
Model-based identification and diagnosis of a porcine model of induced endotoxic shock with hemofiltration
; ; et al
in Mathematical Biosciences (2008), 216(2), 132-139Detailed reference viewed: 14 (4 ULg)
Alteration of Right Ventricular-Pulmonary Vascular Coupling in a Porcine Model of Progressive Pressure Overloading
Ghuysen, Alexandre ; Lambermont, Bernard ; Kolh, Philippe et al
in Shock (Augusta, Ga.) (2008), 29(2), 197-204
In acute pulmonary embolism, right ventricular (RV) failure may result from exceeding myocardial contractile resources with respect to the state of vascular afterload. We investigated the adaptation of RV ... [more ▼]
In acute pulmonary embolism, right ventricular (RV) failure may result from exceeding myocardial contractile resources with respect to the state of vascular afterload. We investigated the adaptation of RV performance in a porcine model of progressive pulmonary embolism. Twelve anesthetized pigs were randomly divided into two groups: gradual pulmonary arterial pressure increases by three injections of autologous blood clot (n = 6) or sham-operated controls (n = 6). Right ventricular pressure-volume (PV) loops were recorded using a conductance catheter. Right ventricular contractility was estimated by the slope of the end-systolic PV relationship (Ees). Afterload was referred to as pulmonary arterial elastance (Ea) and assessed using a four-element Windkessel model. Right ventricular-arterial coupling (Ees/Ea) and efficiency of energy transfer (from PV area to external mechanical work [stroke work]) were assessed at baseline and every 30 min for 4 h. Eaincreased progressively after embolization, from 0.26 +/- 0.04 to 2.2 +/- 0.7 mmHg mL (P < 0.05). Ees increased from 1.01 +/-0.07 to 2.35 +/- 0.27 mmHg mL (P < 0.05) after the first two injections but failed to increase any further. As a result, Ees/Ea initially decreased to values associated with optimal SW, but the last injection was responsible for Ees/Ea values less than 1, decreased stroke volume, and RV dilation. Stroke work/PV area consistently decreased with each injection from 79% +/- 3% to 39% +/- 11% (P < 0.05). In response to gradual increases in afterload, RV contractility reserve was recruited to a point of optimal coupling but submaximal efficiency. Further afterload increases led to RV-vascular uncoupling and failure. [less ▲]Detailed reference viewed: 27 (5 ULg)
Cardiovascular Modelling and Identification in Septic Shock - Experimental validation
Desaive, Thomas ; Lambermont, Bernard ; Ghuysen, Alexandre et al
in IFAC 2008 (2008)Detailed reference viewed: 19 (6 ULg)
Model-based detection of pulmonary embolism using an extended physiologically relevant, cardiovascular model
; ; et al
in Proceedings of Engineering & Physical Sciences in Medicine and Australian Biomedical Engineering Conference (EPSM ABEC 2008) (2008)Detailed reference viewed: 17 (0 ULg)
Making sense of the Chaos: Model-based CVS monitoring and decision support in critical care
; ; et al
in Proceedings of the NZ Physiological Society 2008 Medical Science Congress (MedSci 2008) (2008)Detailed reference viewed: 10 (0 ULg)
Model-based analysis of induced endotoxic shock in pigs with and without hemofiltration,
; ; et al
in Prodeedings of the Engineering & Physical Sciences in Medicine and Australian Biomedical Engineering Conference (EPSM ABEC 2008 (2008)Detailed reference viewed: 21 (1 ULg)