Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: The lungs are hyperexpanded with flattening of the hemidiaphragms and increase in the retrosternal space . The heart is not enlarged . The mediastinal and hilar contours are normal . There is no pleural effusion or pneumothorax . There is no airspace opacity to suggest pneumonia .
    OUTPUT:
    
Severe hyperexpansion may reflect small airways obstruction or emphysema .