Stroke volume estimation by thoracocardiography is better when glottis is closed

Thoracocardiography approach pretends to non-invasively monitor stroke volume by inductive plethysmographic recording of ventricular volume curves by a transducer placed on the chest. The purpose of this study was to investigate the potential of thoracocardiography to estimate stroke volumes while apnea with open glottis. We hypothesized that, when glottis is open, stroke volumes would be better estimated if airways flow curves were taken into account

A 3D discrete model of the diaphragm and human trunk

In this paper, a 3D discrete model is presented to model the movements of the trunk during breathing. In this model, objects are represented by physical particles on their contours. A simple notion of force generated by a linear actuator allows the model to create forces on each particle by way of a geometrical attractor. Tissue elasticity and contractility are modeled by local shape memory and muscular fibers attractors. A specific dynamic MRI study was used to build a simple trunk model comprised of by three compartments: lungs, diaphragm and abdomen. This model was registered on the real geometry. Simulation results were compared qualitatively as well as quantitatively to the experimental data, in terms of volume and geometry. A good correlation was obtained between the model and the real data. Thanks to this model, pathology such as hemidiaphragm paralysis can also be simulated.Comment: published in: "Lung Modelling", France (2006

A Wearable Technology Revisited for Cardio-Respiratory Functional Exploration: Stroke Volume Estimation From Respiratory Inductive Plethysmography

International audienceThe objective of the present study is to extract new information from complex signals generated by Respiratory Inductive Plethysmography (RIP). This indirect cardio-respiratory (CR) measure is a well-known wearable solution. The authors applied time-scale analysis to estimate cardiac activity from thoracic volume variations, witnesses of CR interactions. Calibrated RIP signals gathered from 4 healthy volunteers in resting conditions are processed by Ensemble Empirical Mode Decomposition to extract cardiac volume signals and estimate stroke volumes. Averaged values of these stroke volumes (SVRIP) are compared with averaged values of stroke volumes determined simultaneously by electrical impedance cardiography (SVICG). There is a satisfactory correlation between SVRIP and SVICG (r=0.76, p<0.001) and the limits of agreement between the 2 types of measurements (±23%) satisfies the required criterion (±30%). The observed under-estimation (-58%) is argued. This validates the use of RIP for following stroke volume variations and suggests that one simple transducer can provide a quantitative exploration of both ventilatory and cardiac volumes

Une Architecture Multi-Agents Adaptative pour le Suivi Personnalisé de la Physiologie du Combattant

National audienceDans le domaine du monitoring de signaux médicaux, l'établissement d'un diagnostic est un problème complexe qui repose sur un traitement fiable et sécurisé des signaux multiples observés et également sur le contexte de l'observation. Nous proposons dans cet article une architecture de système pour le diagnostic physiologique de combattants en mission. Le système intègre différents niveaux de pilotage personnalisés et dépendants du contexte en se basant sur un nuage d'agents autonomes interagissants mettant en oeuvre un raisonnement bayésien. Certains agents ont des visions partielles du système, fusionnant les différentes mesures enregistrées par les capteurs, et d'autres, des coalitions dynamiques d'agents, ont une vision globale prenant en compte les degrés de confiance des agents qui les constituent. Les processus de fusion et le pilotage sont ainsi personnalisés et distribués sur plusieurs niveaux permettant une organisation totalement autonome du système qui évolue au gré des observations

SAPHIR - a multi-scale, multi-resolution modeling environment targeting blood pressure regulation and fluid homeostasis.

International audienceWe present progress on a comprehensive, modular, interactive modeling environment centered on overall regulation of blood pressure and body fluid homeostasis. We call the project SAPHIR, for "a Systems Approach for PHysiological Integration of Renal, cardiac, and respiratory functions". The project uses state-of-the-art multi-scale simulation methods. The basic core model will give succinct input-output (reduced-dimension) descriptions of all relevant organ systems and regulatory processes, and it will be modular, multi-resolution, and extensible, in the sense that detailed submodules of any process(es) can be "plugged-in" to the basic model in order to explore, eg. system-level implications of local perturbations. The goal is to keep the basic core model compact enough to insure fast execution time (in view of eventual use in the clinic) and yet to allow elaborate detailed modules of target tissues or organs in order to focus on the problem area while maintaining the system-level regulatory compensations

Calibration of Respiratory Inductance Plethysmograph in Preterm Infants With Different Respiratory Conditions

Summary. Respiratory inductance plethysmography (RIP) is a method for respiratory measurements particularly attractive in infants because it is noninvasive and it does not interfere with the airway. RIP calibration remains controversial in neonates, and is particularly difficult in infants with thoraco-abdominal asynchrony or with ventilatory assist. The objective of this study was to evaluate a new RIP calibration method in preterm infants either without respiratory disease, with thoraco-abdominal asynchrony, or with ventilatory support. This method is based on (i) a specifically adapted RIP jacket, (ii) the least squares method to estimate the volume/motion ribcage and abdominal coefficients, and (iii) an individualized filtering method that takes into account individual breathing pattern. The reference flow was recorded with a pneumotachograph. The accuracy of flow reconstruction using the new method was compared to the accuracy of three other calibration methods, with arbitrary fixed RIP coefficients or with coefficients determined according to qualitative diagnostic calibration method principle. Fifteen preterm neonates have been studied; gestational age was (mean AE SD) 31.7 AE 0.8 weeks; birth weight was 1,470 AE 250 g. The respiratory flow determined with the new method had a goodness of fit at least equivalent to the other three methods in the entire group. Moreover, in unfavorable conditions-breathing asynchrony or ventilatory assist-the quality of fit was significantly higher than with the three other methods (P &lt; 0.05, repeated measures ANOVA). Accuracy of tidal volume measurements was at least equivalent to the other methods, and the breath-by-breath differences with reference volumes were lower, although not significantly, than with the other methods. The goodness of fit of the reconstructed RIP flow with this new method-even in unfavorable respiratory conditionsprovides a prerequisite for the study of flow pattern during the neonatal period

Variations de la capacité résiduelle fonctionnelle chez le prématuré. Interactions avec la ventilation assistée

La capacité résiduelle fonctionnelle (CRF), volume pulmonaire en fin d'expiration normale, est un paramètre essentiel des échanges gazeux. Chez le nourrisson, le maintien du niveau de CRF dépend de l'interaction de différents mécanismes, contrairement à l'équilibre passif observé chez l'adulte. Nous avons essayé d'améliorer la compréhension de ces mécanismes. Dans un premier temps, nous avons confirmé la persistance d'une activité tonique du diaphragme jusqu'en fin d'expiration chez des nourrissons intubés. Cette activité augmente en l'absence de pression expiratoire positive, renforçant l'hypothèse de son implication dans le maintien de la CRF. Nous avons ensuite adapté une méthode de pléthysmographie par inductance pour une utilisation chez le prématuré, y compris en présence d'asynchronisme thoraco-abdominal ou d'assistance ventilatoire. Cette méthode a permis de montrer que chez les prématurés, la variabilité de la CRF est élevée, n'est pas purement aléatoire, et contient une part significative d'autocorrélation. En cas de pathologie respiratoire, le profil de variabilité est différent, avec une autocorrélation plus importante. Cela suggère des retours à l'état antérieur plus lents après perturbation du niveau de CRF. Chez les nourrissons sous assistance respiratoire, l'autocorrélation est encore plus élevée. La caractérisation de la variabilité de la CRF, reflet du degré de liberté du système de contrôle, et la mesure de l'activité tonique du diaphragme, reflet des efforts du nourrisson pour augmenter la CRF, devraient permettre d'améliorer encore la compréhension de la régulation de la CRF, et d'améliorer la prise en charge ventilatoire de ces patients.Functional residual capacity (FRC), the lung volume at the end of a normal expiration, is a key parameter in gas exchanges. In infants, FRC is actively maintained by different mechanisms, as opposed to the passive equilibrium observed in adults. In the present work, we tried to increase the understanding of FRC regulation. We first established a method to quantify diaphragm electrical activity during expiration. We then confirm the persistence of tonic diaphragmatic activity until the end of expiration in intubated infants. This tonic activity rises in absence of positive expiratory pressure, suggesting a role in FRC control. Secondly, we have adapted a respiratory inductive plethysmographic method for its use in infants, even in presence of thoraco-abdominal asynchrony or ventilatory assist. Using this method, we have shown that in premature infants, FRC variability is high, non-random, and contains significant autocorrelation. In patients with respiratory distress, a different variability pattern was observed, with a higher and prolonged autocorrelation. This pattern suggests that FRC returns to baseline more slowly after a perturbation in these patients. In patients under assisted ventilation, autocorrelation was even higher and more prolonged. Characterization of FRC variability, which probably reflects the degrees of freedom of the regulation system, and tonic diaphragmatic activity quantification, which probably illustrates the infant s efforts to maintain the FRC level, will probably help us better understand the FRC regulation in infants in different clinical conditions, and to improve the respiratory management of these patients.GRENOBLE1-BU Sciences (384212103) / SudocSudocFranceF

A 3D discrete model of the diaphragm and human trunk

International audienceIn this paper, a 3D discrete model is presented to model the movements of the trunk during breathing. In this model, objects are represented by physical particles on their contours. A simple notion of force generated by a linear actuator allows the model to create forces on each particle by way of a geometrical attractor. Tissue elasticity and contractility are modeled by local shape memory and muscular fibers attractors. A specific dynamic MRI study was used to build a simple trunk model comprised of by three compartments: lungs, diaphragm and abdomen. This model was registered on the real geometry. Simulation results were compared qualitatively as well as quantitatively to the experimental data, in terms of volume and geometry. A good correlation was obtained between the model and the real data. Thanks to this model, pathology such as hemidiaphragm paralysis can also be simulated

Détection et modélisation de la limitation de débit à l'expiration en ventilation artificielle

L'étude porte sur le phénomène de limitation de débit à l'expiration chez les patients sous ventilation mécanique, avec un double objectif, détecter cliniquement ce phénomène, qui passe souvent inaperçu chez des patients ventilés et le modéliser. Cet évènement est fréquemment rencontré chez les patients souffrant de bronchopneumopathies chroniques obstructives (BPCO). Nous avons mis au point une méthode non invasive de détection de la limitation de débit à l'expiration basée sur la construction de courbes isovolume pression-débit (IVPF), chez des patients ventilés chez lesquels un test de PEEP est effectué. Cette méthode se veut simple et pratique d'utilisation en routine clinique. Nous avons aussi établi un modèle mathématique mono-alvéolaire et deux modèles bi-alvéolaires, non linéaires, décrivant le comportement mécanique du système respiratoire des patients ventilés. De plus, ces modèles permettent de simuler l'effet d'une pression positive appliquée pendant l'expiration (PEEP), technique utilisée dans le but d'améliorer l'écoulement d'air dans les voies aériennes. Ces modèles mathématiques s'appuient en grande partie sur un modèle physique préexistant et permettent de rendre compte de la levée de limitation expiratoire de débit grâce à l'application d'une PEEP et permettent de suivre l'évolution du niveau d'hyperinflation pulmonaire dynamique et des résistances du système respiratoire. Ces modèles illustrent l'intérêt thérapeutique de l'application d'une PEEP chez des patients présentant une limitation de débit à l'expiration. Le modèle mono-alvéolaire a été modifié afin de simuler l'épreuve d'expirations forcées chez les souris et tenter d'expliquer les résultats obtenus expérimentalement.The study focuses on the phenomenon of expiratory airflow limitation in mechanically ventilated patients, with a double aim, the clinical detection of this event which often goes unrecognised in ventilated patients and its modelling. This phenomenon is often seen in patients with chronic obstructive pulmonary diseases (COPD). We established a non invasive method to detect flow limitation by the way of isovolume pressure-flow curves (IVPF), in mechanically ventilated patients undergoing tests of PEEP. This non invasive method can easily be implemented in ICU. We also propose a mono-alveolar and two bi-alveolar non linear mathematical models, describing the mechanical behaviour of the respiratory system of ventilated patients exhibiting expiratory airflow limitation. Moreover this model should simulate applied positive end-expiratory pressure (PEEP) effects during expiration, a process used in order to improve airflow in the airways. Those mathematical models are based on an existing physical model and allow pointing to the removal of airflow expiratory limitation by way of PEEP levels and following the behaviour of dynamic pulmonary hyperinflation and resistances of the respiratory system. This illustrates the therapeutics interest of PEEP in expiratory airflow limited patients. The mono-alveolar mathematical model has been modified to simulate maneuvers of forced expirations in mice, and to try to explain the experimental results obtained.GRENOBLE1-BU Médecine pharm. (385162101) / SudocPARIS-BIUP (751062107) / SudocSudocFranceF