Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: A frontal semi-upright view of the chest was obtained portably . Compared to the prior study , there is no change . Linear opacities at the lung bases are atelectasis . The epidural catheter and right chest tube are unchanged in position . No pneumothorax or substantial pleural effusion . Cardiac and mediastinal silhouettes are stable .
    OUTPUT:
    
No change from 5 : 50 a .m . , four hours earlier .