Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Lung volumes are low with mild bibasilar atelectasis , slightly improved compared to the prior exam . There is moderate cardiomegaly . The hilar and mediastinal contours are exaggerated due to low lung volumes which are otherwise unremarkable . Median sternotomy and surgical clips are seen projecting over the mediastinum . Visualized osseous structures are unremarkable . There is no evidence of a pneumothorax .
    OUTPUT:
    
Improved aeration of the lungs with persistent mild bibasilar atelectasis .