The unrevealed aspect of the autonomic nervous system in the heart-lung interaction: from lab to bedside

Cette thèse aborde l'implication du système nerveux autonome dans l'interaction coeur poumon. La première partie se focalise sur le rôle du système nerveux sympathique dans le développement de l'hypertension pulmonaire (HTP). L'inhibition du système sympathique par le carvedilol n'a pas fourni d'évidence quant à la prévention du développement de l'HTP dans deux modèles expérimentaux. En deuxième partie, l'implication du système parasympathique dans la genèse de l'hyperreactivité bronchique dans un modèle expérimental avec inflammation chronique des voies aériennes a été investigué. L'inhibition de ce système nerveux par l'atropine a induit une réactivité bronchique augmentée quand les animaux étaient exposés à l'allergène. En dernière partie, une étude clinique a été effectuée pour explorer l'interaction coeur poumon chez des patients souffrant d'HTP secondaire à une insuffisance mitrale. L'amélioration des résistances des voies aériennes après correction chirurgicale chez ces enfants confirme cette interaction coeur-poumon

Effect of surfactant on regional lung function in an experimental model of respiratory distress syndrome in rabbit

We assessed the changes in regional lung function following instillation of surfactant in a model of respiratory distress syndrome (RDS) induced by whole lung lavage and mechanical ventilation, in 8 anaesthetized, paralyzed, and mechanically ventilated New-Zealand White rabbits. Regional specific ventilation (sV· ) was measured using K-edge subtraction synchrotron CT imaging during xenon washin. Lung regions were classified as poorly-aerated (PA), normally aerated (NA) or hyperinflated (HI) based on regional density. A functional category was defined within each class, based on sV· distribution (High, Normal, and Low). Airway resistance (Raw), respiratory tissue damping (G) and elastance (H) were measured by forced oscillation technique (FOT) at low frequencies before and after whole lung saline lavage-induced (100 ml/kg) RDS, and 5 and 45 minutes after intratracheal instillation of beractant (75 mg/kg). Surfactant instillation improved Raw, G and H (p<0.05, respectively) and gas exchange and decreased atelectasis (p<0.001). It also significantly improved lung aeration and ventilation in atelectatic lung regions. However, in regions that had remained normally-aerated after lavage, it decreased regional aeration and increased sV· (p<0.001) and sV· heterogeneity. Although surfactant treatment improved both central airway and tissue mechanics and improved regional lung function of initially poorly-aerated and atelectatic lung, it deteriorated regional lung function when local aeration was normal prior to administration. Local mechanical and functional heterogeneity can potentially contribute to the worsening of RDS, and gas exchange. These data underscore the need for reassessing the benefits of routine prophylactic vs. CPAP and early "rescue" surfactant therapy in very immature infants

Pressure-regulated volume control vs. volume control ventilation in healthy and injured rabbit lung: An experimental study

It is not well understood how different ventilation modes affect the regional distribution of ventilation, particularly within the injured lung

Synchrotron Imaging Shows Effect of Ventilator Settings on Intrabreath Cyclic Changes in Pulmonary Blood Volume

Despite the importance of dynamic changes in the regional distributions of gas and blood during the breathing cycle for lung function in the mechanically ventilated patient, no quantitative data on such cyclic changes are currently available. We used a novel gated synchrotron computed tomography imaging to quantitatively image regional lung gas volume (Vg), tissue density, and blood volume (Vb) in six anesthetized, paralyzed, and mechanically ventilated rabbits with normal lungs. Images were repeatedly collected during ventilation and steady-state inhalation of 50% xenon, or iodine infusion. Data were acquired in a dependent and nondependent image level, at zero end-expiratory pressure (ZEEP) and 9 cm H2O (positive end-expiratory pressure), and a tidal volume (Vt) of 6 ml/kg (Vt1) or 9 ml/kg (Vt2) at an Inspiratory:Expiratory ratio of 0.5 or 1.7 by applying an end-inspiratory pause. A video showing dynamic decreases in Vb during inspiration is presented. Vb decreased with positive end-expiratory pressure (P = 0.006; P = 0.036 versus Vt1-ZEEP and Vt2-ZEEP, respectively), and showed larger oscillations at the dependent image level, whereas a 45% increase in Vt did not have a significant effect. End-inspiratory Vb minima were reduced by an end-inspiratory pause (P = 0.042, P = 0.006 at nondependent and dependent levels, respectively). Normalized regional Vg:Vb ratio increased upon inspiration. Our data demonstrate, for the first time, within-tidal cyclic variations in regional pulmonary Vb. The quantitative matching of regional Vg and Vb improved upon inspiration under ZEEP. Further study is underway to determine whether these phenomena affect intratidal gas exchange

Early and Late Postoperative Tachyarrhythmias in Children and Young Adults Undergoing Congenital Heart Disease Surgery

The population of patients with congenital heart disease is constantly growing with an increasing number of individuals reaching adulthood. A significant proportion of these children and young adults will suffer from tachyarrhythmias due to the abnormal anatomy, the hemodynamic burden, or as a sequela of surgical treatment. Depending on the underlying mechanism, arrhythmias may arise in the early postoperative period (hours to days after surgery) or in the late postoperative period (usually years after surgery). A good understanding of the electrophysiological characteristics and pathophysiological mechanisms is therefore crucial to guide the therapeutic approach. Here, we synthesize the current state of knowledge on epidemiological features, risk factors, pathophysiological insights, electrophysiological features, and therapy regarding tachyarrhythmias in children and young adults undergoing reparative surgery for congenital heart disease. The evolution and latest data on treatment options, including pharmacological therapy, ablation procedures, device therapy decision, and thromboprophylaxis, are summarized. Finally, throughout this comprehensive review, knowledge gaps and areas for future research are also identified