Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Patient is status post median sternotomy . The cardiac and mediastinal silhouettes are stable with prominence of the mediastinum stable . There may be a trace left pleural effusion , but no large pleural effusion is seen . There is been improved aeration of the left lower lobe . No pneumothorax is seen .
    OUTPUT:
    
Possible trace left pleural effusion . Otherwise , no acute cardiopulmonary process . Improved aeration of the left lower lobe .