Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: No evidence of pneumothorax . Mediastinal and hilar contours are normal . Volumes are persistently low , however , lungs appear stable with focal linear opacities at the bases that likely represent atelectasis . No pleural effusion is seen . No free air under the diaphragms .
    OUTPUT:
    
No evidence of pneumothorax . Persistently low lung volumes with bibasilar atelectasis .