Bronchial inhalation of amiloride chlorhydrate has been suggested for a number of years in the treatment of the pulmonary disease in cystic fibrosis. However, physiotherapy remains invaluable in the struggle in containing pulmonary infections in this disorder. Physiotherapy may lead to a transient fall in the arterial oxygen as can sessions of nebuliser therapy which precedes physiotherapy. The originality of the system studied and proposed here for the administration of medication depends on an electronic control which guarantees that there is the nebulisation of a constant volume of medication with each inspiration. Triggered by inspiration the active principle nebulised is perfectly co-ordinated to the inspiratory cycle. A comparative chromatography carried out in this slides of silica-gel have enabled us to verify the absence of any degradation of the active principle contained in the nebuliser solution during the ten minutes period of aerosol therapy. Thus a quantification of the administered dose of Amiloride Chlorhydrate is made possible. In association with oxygen it enables an efficacious preparation of respiratory physiotherapy to children. As the expiratory tubing ends in a filter the fraction of the oxygen inhaled by the patient remains very high; 80% (V/V) of the medication is emitted in the form of liquid particles whose diameter lies between 0.5 and 5 micrometers. In practice in order to humidify the sputum and to restore the oximetry before the physiotherapy sessions, it seemed to us an interesting possibility to administer Amiloride Chlorhydrate and oxygen simultaneously. This is achieved in hospital by using wall-mounted oxygen (at a gas pressure of 3.5 bars).(ABSTRACT TRUNCATED AT 250 WORDS)