Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: The patient is status post median sternotomy and CABG . Lung volumes remain slightly low . Heart size is mildly enlarged but unchanged . The mediastinal and hilar contours are similar . Crowding of the bronchovascular structures is demonstrated without pulmonary edema . Patchy bibasilar airspace opacities likely reflect atelectasis in the setting of low lung volumes . No focal consolidation , pleural effusion or pneumothorax is present . There are mild multilevel degenerative changes noted in the thoracic spine .
    OUTPUT:
    
Low lung volumes with patchy atelectasis in the lung bases .