Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: AP upright and lateral views of the chest provided . Midline sternotomy wires again noted as well as a valve replacement . Lung volumes are low . The lungs appear clear without focal consolidation , large effusion or pneumothorax . No signs of congestion or edema . Cardiomediastinal silhouette is stable . Bony structures are intact . No free air below the right hemidiaphragm .
    OUTPUT:
    
No acute findings . Limited by low lung volumes .