Wouter H van Geffen,1,2 Bita Hajian,3 Wim Vos,4 Jan De Backer,4 Anthony Cahn,5 Omar S Usmani,6 Cedric Van Holsbeke,4 Massimo Pistolesi,7 Huib AM Kerstjens,2 Wilfried De Backer3 1Department of Respiratory Medicine, Medical Centre Leeuwarden, Leeuwarden, the Netherlands; 2Department of Pulmonary Diseases, University Medical Center Groningen, Groningen Research Institute for Asthma and COPD, University of Groningen, the Netherlands; 3Department of Pulmonary Diseases, Antwerp University Hospital, Antwerp, Belgium; 4FLUIDDA nv, Kontich, Belgium; 5GlaxoSmithKline R&D, Stevenage, UK; 6Faculty of Medicine, National Heart & Lung Institute, Imperial College London, London, UK; 7Department of Experimental and Clinical Medicine, Section of Respiratory Medicine, University of Florence, Florence, Italy Background: Exacerbations of COPD are a major burden to patients, and yet little is understood about heterogeneity. It contributes to the current persistent one-size-fits-all treatment. To replace this treatment by more personalized, precision medicine, new insights are required. We assessed the heterogeneity of exacerbations by functional respiratory imaging (FRI) in 3-dimensional models of airways and lungs. Methods: The trial was designed as a multicenter trial of patients with an acute exacerbation of COPD who were assessed by FRI, pulmonary function tests, and patient-reported outcomes, both in the acute stage and during resolution. Results: Forty seven patients were assessed. FRI analyses showed significant improvements in hyperinflation (a decrease in total volume at functional residual capacity of -0.25±0.61 L, p≤0.01), airway volume at total lung capacity (+1.70±4.65 L, p=0.02), and airway resistance. As expected, these improvements correlated partially with changes in the quality of life and in conventional lung function test parameters. Patients with the same changes in pulmonary function differ in regional disease activity measured by FRI. Conclusion: FRI is a useful tool to get a better insight into exacerbations of COPD, and significant improvements in its indices can be demonstrated from the acute phase to resolution even in relatively small groups. It clearly visualizes the marked variability within and between individuals in ventilation and resistance during exacerbations and is a tool for the assessment of the heterogeneity of COPD exacerbations. Keywords: COPD exacerbations, FRI, hyperinflation, chronic obstructive pulmonary disease, symptoms, heterogeneity