The CARMUCI Study Design: A Double‐Blind, Cross‐Over Sham‐Controlled Trial of Indoor Air Purification in People With Cystic Fibrosis and Primary Ciliary Dyskinesia

ABSTRACT Background People with cystic fibrosis (pwCF) and primary ciliary dyskinesia (pwPCD) are particularly vulnerable to the harmful effects of air pollution due to the impairment of mucociliary clearance (MCC). Despite growing evidence supporting the use of indoor air purification in common lung conditions, its role in CF and PCD remains unexplored. Methods The Clean Air for Rare MCC dIsorders (CARMUCI) study is a randomized, double‐blind, cross‐over, sham‐controlled trial aiming to evaluate the impact of indoor air purification on the respiratory health of pwCF and pwPCD (children and adults) in Cyprus. Sixty‐two participants will receive two 3‐month intervention periods using identical‐looking air purifiers: one 3‐month period with active filtration via high‐efficiency filters and one 3‐month period with a sham unit. Primary outcome will be a mean difference of at least 10% change in lung clearance index, and secondary outcomes will include spirometry, pulmonary exacerbations, inflammatory biomarkers, and health‐related quality of life. Exposure to indoor particulate matter (PM) will be continuously monitored using device operation logs and wearable activity trackers. Results By August 2025, 24 pwCF and 26 pwPCD (20 females, age: 31 16.1 years) have been enrolled. CARMUCI continues enrollment and will start data collection in September 2025. Results are expected to provide novel evidence on the efficacy of air purification in reducing indoor PM exposure and improving respiratory outcomes in people with chronic MCC disorders. Conclusion CARMUCI trial first results are expected in late‐2027 and may inform future clinical guidelines and environmental health strategies for managing rare MCC disorders.