Low-dose CT for Diagnosis of Pneumonia in COPD Exacerbations and Comparison of the Inflammatory Profile.

\* Hypothesis: There is an underdiagnosis of pneumonia in COPD (Chronic Obstructive Pulmonary Disease) exacerbations which could be demonstrated by performing low-dose chest CT. Differences in the inflammatory profile in sputum and blood in patients with and without pneumonia can be seen. \* Objective: To assess the degree of underdiagnosis of pneumonia in COPD exacerbations, using chest low-dose CT and to compare clinical and inflammatory differences in blood and sputum between patients with and without pneumonia. \*Material and Methods: Prospective observational study including 75 patients with the diagnosis of COPD at the time of an exacerbation and with criteria for a respiratory tract infection. At the time of inclusion clinical features, blood and sputum analysis, chest X-ray and chest low-dose CT are performed. The investigators divide the patients into two groups according to the existence of pneumonia and the inflammatory pattern in blood (inflammatory markers) and sputum (cell populations and inflammatory markers) is compared between the two branches.