Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: The lungs are hyperinflated , suggesting small airway obstruction or even emphysema , but clear of focal abnormality . There has not been much change in lung volumes since at least ___ . The cardiomediastinal silhouette , hilar structures , and pleural surfaces are normal . No pneumothorax .
    OUTPUT:
    
No evidence of pneumonia . A chronic hyperinflation , either emphysema or small airway obstruction .