Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Patient is status post median sternotomy and aortic valve replacement . Heart size remains mildly enlarged , unchanged . Mediastinal and hilar contours are similar . Lung volumes are low with mild crowding of the bronchovascular structures but no overt pulmonary edema . Patchy opacities in the lung bases likely reflect areas of atelectasis . No pleural effusion or pneumothorax is clearly visualized . A right - sided PICC tip terminates in the low SVC .
    OUTPUT:
    
Low lung volumes with probable bibasilar atelectasis .