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

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.

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 ISRCTN registry (ID 64994816). 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.

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).

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.