Chest physiotherapy plays a crucial role in treatment of lung disease in cystic fibrosis (CF). New airway clearance techniques (ACTs) adapted to individual needs are still being sought to achieve the best effect of airway clearance. The primary aim of this study is to assess the efficacy of a new ACT (Simeox) on pulmonary function in children with CF. 40 CF patients with stable respiratory function will be randomized 1:1 to Simeox or conventional chest physiotherapy (CCPT) therapy (control group) and treated at home during 1 month. After a short washout period, patients will be treated at home onto the alternative treatment for 1 month (crossover design). Lung function, quality of life, pulmonary exacerbation and safety will be evaluated at 1 month for each therapy period.

Inclusion Criteria:

• Subject and his or her legally appointed and authorized representative will agree for treatment with Simeox technology
• willing and able to cooperate and learn new technic of drainage.
• age 8-18 years, on the date of admission to hospital.
• confirmed diagnosis of CF as determined by the investigator.
• able to perform pulmonary tests

Exclusion Criteria:

History of any illness or any clinical condition that, in the opinion of the investigator, might confound the cooperation or the results of the study or pose an additional risk to the subject in using study technology. This includes, but is not limited to, the following:

• contraindications to bronchial chest physiotherapy
• hemoptysis
• pneumothorax
• heart disease
• recent chest surgery
• recent chest injury
• history of lung transplantation