Characterisation of respiratory mechanics in adults with CF using dynamic chest radiography.

Background: As the lifespan of people with CF (pwCF) improves, sensitive markers of lung health are needed. Dynamic chest radiography (DCR) is a low ionising radiation dose cineradiographic imaging system that provides real-time information on moving thoracic structures. We examined whether DCR provides quantitative motion analysis that correlates with pulmonary function, anthropometric and clinical variables in pwCF, to explore DCR as a marker of lung health.

Methods: In this prospective, observational, single-centre, non-controlled study, participantsunderwent DCR and spirometry. We measured DCR parameters such as diaphragm motion and change in projected lung area (ΔPLA). The study is registered on the ________ registry (ID __________). Correlation was assessed using Spearman's coefficient, and relationships between DCR and spirometric variables using linear regression modelling. Descriptive statistics are reported as mean ± standard deviation and median (interquartile range) as appropriate.

Results: We assessed 129 adult pwCF (age 29[12] years, 48 female, ppFEV1 69±25). Average inspiratory lung area (PLAinsp) was 424±72cm2, and expiratory lung area (PLAexp) 325±68cm2. Left diaphragm motion range was 34±12mm, right 29±12mm. ΔPLA correlated with FEV1 (ρ=0.70,P<0.001). PLAinsp correlated with FVC (ρ=0.56,P<0.001). PLAexp correlated with FEV1/FVC ratio (ρ=-0.49,P<0.001). BMI correlated with ΔPLA (ρ=0.29,P=0.001) and deep breathing hemidiaphragm excursion (right, ρ=0.4,P<0.001; left 0.39,P<0.001).

Conclusions: This study is the first to describe diaphragm motion and projected lung areas using DCR in non-exacerbating adult pwCF, and complements work by our group demonstrating change in DCR parameters in pwCF undergoing pharmacological interventions. DCR shows potential as a tool to investigate lung health in pwCF.