Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: AP portable upright view of the chest . No free air is seen below the right hemidiaphragm . Midline sternotomy wires and mediastinal clips are again noted . The heart remains mildly enlarged . Lung volumes are low . There is mild atelectasis in the lower lungs . Right CP angle partially excluded . No large effusion or pneumothorax is seen . No signs of edema . Imaged osseous structures are intact .
    OUTPUT:
    
No free air below the right hemidiaphragm . Stable cardiomegaly .