Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Lung volumes are low though without confluent consolidation . Basilar linear opacities may be due to underinflation , though early pulmonary edema can not be excluded . There is no pneumothorax . No vascular congestion or large pleural effusions are evident . Mediastinal and hilar contours are within normal limits without evidence of developing mediastinal hematoma . The cardiac silhouette is normal in size . A known sternal fracture is not well evaluated on this single frontal chest radiograph .
    OUTPUT:
    
1 . No evidence of mediastinal hematoma . 2 . Known sternal fracture , not well evaluated on this single frontal view . 3 . Low lung volumes , though early basilar mild pulmonary edema can not be excluded .