Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Lordotic positioning . There is relative hyperlucency of the upper and mid zones on both sides , suggesting severe emphysema . There is slight upper zone redistribution . There are patchy opacities at both lung bases . This may reflect crowding of vessels at the lung bases due to emphysematous changes . However , it is more pronounced , particularly on the left , compared with ___ and ___ . Thus , the possibility of superimposed infectious infiltrate can not be excluded . Asymmetric distribution of CHF is considered less likely . Blunting of the costophrenic angles is grossly unchanged . Vertical linear lucency in the left paratracheal region adjacent to the aortic knob is similar to ___ and therefore unlikely to represent pneumomediastinum . Otherwise , no evidence of pneumomediastinum or pneumothorax .
    OUTPUT:
    
1 . Severe emphysema with vascular crowding / scarring at bases . 2 . Opacity at left greater than right base is more pronounced compared to prior films and raises question of a superimposed pneumonic infiltrate , particularly at the left base . Please see comment .