Supplementary Material for: Dynamic-Ventilatory Digital Radiography in Air Flow Limitation: A Change in Lung Area Reflects Air Trapping

posted on 29.04.2020 by Ohkura N., Kasahara K., Watanabe S., Hara J., Abo M., Sone T., Kimura H., Takata M., Tamura M., Matsumoto I., Nakade Y., Sanada S., Tanaka R.
Objective: The aim of this study was to determine the utility of dynamic-ventilatory digital radiography (DR) for pulmonary function assessment in patients with airflow limitation. Methods: One hundred and eighteen patients with airflow limitation (72 patients with lung cancer before surgery, 35 patients with chronic obstructive pulmonary disease [COPD], 6 patients with asthma, and 5 patients with asthma-COPD overlap syndrome) were assessed with dynamic-ventilatory DR. The patients were instructed to inhale and exhale slowly and maximally. Sequential chest X-ray images were captured in 15 frames per second using a dynamic flat-panel imaging system. The relationship between the lung area and the rate of change in the lung area due to respiratory motion with respect to pulmonary function was analyzed. Results: The rate of change in the lung area from maximum inspiration to maximum expiration (Rs ratio) was associated with the RV/TLC ratio (r = 0.48, p < 0.01) and the percentage of the predicted FEV1 (r = –0.33, p < 0.01) in patients with airflow limitations. The Rs ratio also decreased in an FEV1-dependent manner. Conclusion: The rate of change in the lung area due to respiratory motion evaluated with dynamic DR reflects air trapping. Dynamic DR is a potential tool for the comprehensive assessment of pulmonary function in patients with COPD.