Assessing respitatory muscle activity with ¹⁸F-FDG-PET/CT in patients with COPD

The purpose of this study was to investigate the metabolic activity of the respiratory muscles in patients with chronic obstructive pulmonary diseases (COPD) and correlate with pulmonary function test results. Thirty-three male patients with a past medical history of smoking and COPD referred to 2-deoxy-2-[¹⁸F]-fluorodeoxyglucose positron emission tomography/computed tomography (¹⁸F-FDG-PET/CT) because of clinical suspicion of pulmonary cancer were included. The degree of ¹⁸F-FDG uptake was visually quantified (grade 0-3) in the respiratory muscles of the neck, intercostal muscles, and abdominal muscles using mediastinal blood pool uptake and liver uptake as references. Visual grade of ¹⁸F-FDG uptake was compared to forced expiratory volume in 1 second/forced vital capacity (FEV₁/FVC) and FEV₁ percent predicted (FEV₁ % pred) by the Wilcoxon-type test for trend. We found significant correlation between the visual grading score and both FEV₁/FVC (P=0.017) and FEV₁ % predicted (P=0.045) for the intercostal muscles. Grade was not significantly associated with pulmonary function tests in either the neck or abdominal muscle groups. ¹⁸F-FDG-PET/CT of the respiratory muscles may have potential in characterization of COPD. Future prospective studies with a larger number of subjects should be undertaken to better understand respiratory muscle physiology in patients with COPD.