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Effets cliniques, biologiques et aspects techniques de la ventilation non invasive

Abstract : Chronic alveolar hypoventilation is considered as a pejorative factor of several respiratory diseases outcomes. However, its pathophysiological impact has not been studied in a convincing way. This thesis aimed to assess moderate alveolar hypoventilation consequences during restrictive chronic respiratory failure and the effects of its treatment by non-invasive ventilation (NIV).
We have shown that Obesity Hypoventilation Syndrome patients (OHS) had more severely impaired endothelial function and higher systemic low-grade inflammation than simple obese patients. Arterial PaCO2 was correlated with endothelial dysfunction (Borel et al, manuscript in preparation). We have also reported that in OHS, the proportion of REM-sleep time spent in hypoventilation was related to lowered CO2 ventilatory response and to excessive diurnal sleepiness. Non-invasive ventilation improved objective diurnal vigilance (Chouri-Pontarollo et al Chest 2007). Currently, we are conducting the first randomized NIV versus observation during one month study in OHS. The intermediate analysis showed that one month of nocturnal NIV led to a diurnal PaCO2, an improvement of sleep structure and an increase of total lung capacity. However, neither cardiovascular nor metabolic parameters were modified.
When NIV was used during exercise, in patients with chronic thoracic restrictive respiratory failure, minute ventilation and exercise tolerance were improved (Borel et al, Resp Med 2008). In these patients, long term training with NIV had no additional benefits as to training in spontaneous breathing, except for the most severe of them. For those later patients, training with NIV lead to a larger improvement in six minutes walking distance and in quality of live, particularly in their fatigue.
We also focused on the impact of intentional leak levels of different masks on the performance of ventilators designed for bi-level positive pressure ventilation. Increase of intentional leaks significantly impaired the capacity of ventilators to attain and maintain preset inspiratory pressure and could decrease tidal volume. These significant effects occurred mainly for intentional leaks above 40 l/min (for an inspiratory pressure of 14 cmH2O) (Borel et al, Chest 2008 in press).
Conclusion: Chronic alveolar hypoventilation may be considered as one of the patho-physiological factors of endothelial dysfunction, inflammation, sleepiness and exercise intolerance. In spite of technological limitations of bi-level pressure machines currently used, nocturnal NIV corrects alveolar hypoventilation in OHS patients; however its short term and long term impacts on inflammation and endothelial dysfunction remain uncertain. During respiratory rehabilitation program, using NIV during exercise improves exercise capacities and quality of life for the most severe restrictive respiratory failure patients.
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Submitted on : Wednesday, September 2, 2009 - 11:36:33 PM
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Jean Christian Borel. Effets cliniques, biologiques et aspects techniques de la ventilation non invasive. Sciences du Vivant [q-bio]. Université Joseph-Fourier - Grenoble I, 2008. Français. ⟨tel-00413011⟩

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