Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Semi-upright portable chest radiograph demonstrates interval improved aeration of the bilateral upper lungs ; however , there is persistent if not slightly improved bibasilar opacifications , possibly due to atelectasis and bilateral pleural effusions , though superimposed infectious process is not excluded .
    OUTPUT:
    
Improved aeration of upper lungs with stable if not slightly improved bibasilar opacifications , likely a combination of atelectasis and effusions , though pneumonia is not excluded .