Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Since prior , endotracheal tube has been retracted and now ends at the level of the carina it can be retracted approximately 3 cm , for more optimal positioning . There has been interval improvement in aeration of the left upper lung however there remains left basilar opacity . Air is a parrot mediastinal widening , of unclear significance . Right lung remains clear .
    OUTPUT:
    
1 . Interval retraction of endotracheal tube which still appears to low at the level of the carina and can be pulled back approximately 3 .0 cm . 2 . Improvement in left upper lobe aeration with continued opacity at the left base . 3 . Apparent widening of the mediastinum , may be due to supine technique .