Clean Air for Rare MUcociliary Clearance dIsorders (CARMUCI)

Introduction Exposure to airborne particulate matter (PM) is a well-established risk factor for respiratory morbidity, especially in vulnerable populations. While the health effects of PM are well documented in asthma and chronic obstructive pulmonary disease, much less is known about its impact on rarer congenital pulmonary disorders, such as cystic fibrosis (CF) and primary ciliary dyskinesia (PCD). These conditions are characterized by severely impaired mucociliary clearance (MCC), a primary defence mechanism of the airways against inhaled pollutants and pathogens.

Defective MCC predisposes people with CF (pwCF) and PCD (pwPCD) to chronic infections, persistent airway inflammation, and progressive lung function decline. While airborne PM are relatively less harmful to healthy and/or less susceptible individuals, the inability of pwCF and pwPCD to effectively expel mucous from their airways enables inhaled pathogens and particles with the toxic substances they carry to remain in the airways for greater time periods compared to the general population. Although there are no reports in pwPCD, evidence from observational studies in pwCF suggests that exposure to air pollution accelerates disease progression. To date, no interventional studies have evaluated indoor air quality improvements as a protective measure in either of these populations.

The Eastern Mediterranean region, and Cyprus in particular, frequently experiences exceedances of World Health Organization (WHO) thresholds for PM levels, due to both anthropogenic emissions and transboundary desert dust events. As most of the time in western societies is spent in indoor environments, use of indoor air purification may result in an important exposure reduction to airborne PM. Previous studies from Cyprus and elsewhere have reported that indoor air purification can reduce the negative impacts of air particulates on chronic lung diseases such as asthma.

In the recent MEDEA project, air purifiers with high efficiency particulate air (HEPA) filters were found to reduce indoor levels of fine particles by about 50% during both dust and non-dust storm days and led to improvement in asthma symptoms and lung function compared with the control leg. Beyond filtering air pollutants, most commercial HEPA air purifiers also filter several types of bacteria and viruses, and thus they can also reduce transmission of infectious agents indoors. These effects of HEPA filters may be beneficial for pwCF and pwPCD who are predisposed to severe life-long respiratory morbidity.

The objective of the CARMUCI trial is to assess for the first time the impact of indoor air purification on respiratory health outcomes among pwCF and pwPCD, using a randomized, cross-over, sham-controlled design. More specifically, CARMUCI will 1) provide field-based evidence for the effectiveness of air purification to reduce concentrations of indoor PM in the households of pwCF and pwPCD; and, 2) demonstrate the benefits of indoor air purification on respiratory morbidity particularly on lung function, clinical exacerbations, symptoms control, inflammatory biomarkers and health-related quality of life (HRQoL) in pwCF and pwPCD.