Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: A single portable radiograph of the chest was acquired . There is minimal bibasilar dependent atelectasis . The lungs are otherwise clear . The heart is mildly enlarged . The mediastinal contours are normal . Aortic knob calcifications are seen . There are no pleural effusions . No pneumothorax is seen . The patient is status post midline sternotomy . Degenerative changes of the thoracic spine are noted .
    OUTPUT:
    
No acute cardiac or pulmonary process .