Chest published an article regarding risk of chronic pulmonary obstructive disease and pulmonary embolism. There are different reported risk from 3% to 30%. In this study, prevalence of pulmonary embolism in unexplained acute exacerbation of COPD reported as high as 16%. We should be worry about PE in patients with unexplained acute exacerbation of COPD who have pleuritic chest pain and signs of cardiac failure without clear infectious origin.