Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Heart size is normal . The mediastinal and hilar contours are normal . The pulmonary vasculature is normal . Lungs are clear . Lungs are hyperinflated , and note is made of a saber sheath configuration of the trachea , findings that can be seen in the setting of COPD . No pleural effusion or pneumothorax is seen . There are no acute osseous abnormalities .
    OUTPUT:
    
No acute cardiopulmonary abnormality . Possible COPD . Clinical correlation suggested .