Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: The patient is status post median sternotomy and CABG . Heart size is borderline enlarged . The mediastinal and hilar contours are unchanged . There is crowding of the bronchovascular structures due to low lung volumes without overt pulmonary edema . Patchy bibasilar airspace opacities may reflect atelectasis though infection or aspiration can not be excluded . No pleural effusion or pneumothorax is seen . Multilevel degenerative changes are again noted in the thoracic spine with anterior bridging osteophytes .
    OUTPUT:
    
Low lung volumes . Patchy bibasilar airspace opacities may reflect atelectasis though infection or aspiration can not be completely excluded .