Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: AP view of the chest . ET tube ends 2 .9 cm from the carina . The left subclavian line ends in the upper SVC . Enteric tube ends off the inferior portion of the image . Low lung volumes . Lung aeration is improved compared to prior study , no evidence of edema . There is a retrocardiac opacity may represent atelectasis or pneumonia . Possible small left pleural effusion .
    OUTPUT:
    
Retrocardiac opacity may represent atelectasis or pneumonia . No evidence of edema .