The utility of dynamic chest radiography in patients with asthma, COPD, COVID-19 and ILD: A pilot study

Assessment of breathlessness requires a combination of imaging and lung function testing. Dynamic digital radiography (DDR) of the thorax is an imaging technique that allows physiological and anatomical information to be gathered at the time of chest X-ray and has the potential to significantly streamline diagnostic pathways. The aims of this study were to investigate the acceptability of DDR to patients and explore the correlation between DDR-derived measurements with lung volumes measured using full pulmonary function tests (PFT).

We conducted a single-centre, prospective, pilot study of patients with confirmed asthma, chronic obstructive pulmonary disease (COPD), interstitial lung disease (ILD) or post-COVID-19 infection. Participants underwent DDR and paired PFT between March 2021 and August 2022. Dynamic digital radiography acceptability was measured using a 10-cm visual analogue scale (VAS). Point estimates and exact confidence intervals were used to evaluate participant preference. Digital dynamic radiography would be considered acceptable if the lower bound of the 95% confidence interval (exact) is greater than 50%. Pearson correlation (r) was used to explore associations between DDR measurements and PFT parameters.

40 participants (asthma, n = 11; COPD, n = 9; ILD, n = 11; post-COVID, n = 9) had DDR with adequate image acquisition and PFT. Mean age of participants was 63.38 years (standard deviation 14.89) and 63% were male (25/40). The lower 95% confidence interval threshold for VAS acceptability was 92% for all groups combined and considered acceptable. The projected lung area at end inspiration (PLA_insp) closely correlated with total lung capacity across all disease cohorts (r = 0.80, p < 0.001) and projected lung area at end expiration (PLA_exp) was strongly correlated with residual volume in airways disease (COPD: r = 0.87, p = 0.003; asthma: r = 0.85, p = 0.002).

Dynamic digital radiography is an acceptable investigation for respiratory patients. DDR-derived measurements correlate with lung volumes obtained from PFTs. Larger studies are required to validate DDR as a possible method to identify and monitor air trapping in airways disease, allowing early detection and assessment of treatment effectiveness.