SPutum Induction and Nebuliser deviCEs for Patients With CF

The goal of the SPICE-CF feasibility trial is to learn whether it is feasible to recruit and retain people with cystic fibrosis (CF) who are unable to produce sputum spontaneously in a study comparing two different nebuliser devices for sputum induction. The study will also assess how acceptable and practical the sputum induction procedures are. The main questions it aims to answer are: * Is it feasible to recruit and retain people with cystic fibrosis in a study comparing two nebuliser devices for sputum induction? * Can sputum be successfully obtained using each nebuliser device? * How acceptable are the two nebuliser devices to participants? * How long does sputum induction take with each device? * What microorganisms are identified in sputum collected using each device? * Can a visual scoring system be used to distinguish sputum from saliva and describe sputum characteristics? Researchers will compare a jet nebuliser with an E-flow Rapid nebuliser. Each participant will undergo sputum induction using both devices, with the order in which the devices are used determined at random. Participants will: * Attend two study visits, separated by at least 2 weeks * Receive a bronchodilator before sputum induction * Inhale hypertonic saline using either the jet nebuliser or E-flow Rapid nebuliser * Perform their usual airway clearance technique with supervision from a physiotherapist * Have their lung function, oxygen levels, heart rate, and chest sounds monitored * Provide sputum produced during the procedure for assessment and routine microbiological testing * Complete a brief questionnaire about their experience and the acceptability of each nebuliser device