Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: The patient is status post median sternotomy and valvular surgery . Cardiomediastinal contours are stable in the postoperative period . Improving atelectasis is present at the lung bases , and there are persistent small pleural effusions , left greater than right . No pneumothorax .
    OUTPUT:
    
Improving bibasilar atelectasis and persistent pleural effusions .