"The usefulness of respiratory physiotherapy and its execution modalities remains highly debated even though reviews of the literature show that respiratory physiotherapy is able to improve the drainage of bronchial secretions and pulmonary function tests during cystic fibrosis in periods of stability. Different physiotherapy techniques have been developed but the choice of one or the other facing a patient can not currently be recommended. The VirtualChest project, supported by a grant from the National Agency for Research (ANR), aims to develop and validate a physical model of respiratory physiotherapy (6 stages including model establishment pulmonary: bronchial tree and pulmonary mechanics and parietal [steps 1 and 3], a model of mucus [step 2] and modeling the effect of physiotherapy [step 5]). This project is integrated with stages 3 and 5 of this broad project and aims to get on a limited number of children with cystic fibrosis a proof of concept (prediction of drainage efficiency) and especially to feed the proposed physical models in order to subsequent optimization of the model (step 6). The choice cystic fibrosis of the child was justified by the effect demonstrated respiratory physiotherapy, particularly on respiratory functional criteria, and the fact that the parietal mechanics varies physiologically at this age."

"The clinical study will consist in carrying out, before and after hospital respiratory physiotherapy, a measure impedance of the respiratory system by forced oscillations (IOS, impulsometry: measurement during tidal breathing) and a measurement anatomical dead space (duration of the two measurements: 10 minutes). The physiotherapist will make an initial diagnosis (degree of bronchial obstruction), fill a form describing the modalities of the physiotherapy session (methods used) and will evaluate the sputum volume got. On a limited number of children (n = 6), expiratory flow will be measured during the session of physiotherapy ; these measures will be carried out in hypersecreting children able to support a face mask during the session and having had or before have a chest CT scan within 6 months. The objective is to establish a correlation between sputum volume and the degree of improvement of functional respiratory parameters, to establish criteria of central and / or peripheral effect of physiotherapy (""simple"" modeling obtained from measurements impedance of the respiratory system) and to obtain the flow rates necessary and sufficient to mobilize bronchial secretions. The data from this phase will allow to fuel the ""complex"" physical model (distribution mucus in the airways). Moreover, for each of the patients will be recovered the possible scanner performed within ± 6 months of the physiotherapy session which will allow the extraction of the morphology of the airways of the patient. The goal is to get in at least 6 patients a specific morphology of the airways and determine if this morphology implementation allows to improve the model compared to the use of generic modeling or airway tree. A total of 30 elderly Cystic Fibrosis children at least 4 years will be prospectively included."

Inclusion Criteria:

• Diagnosis of cystic fibrosis
• Physiotherapy session is programmed

Exclusion Criteria:

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