Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Supine portable AP view of the chest was provided . Tip of the endotracheal tube resides 3 .6 cm above the carina . There is retrocardiac linear density likely reflective of left lower lobe atelectasis . The lungs appear otherwise clear , though lung volumes are low . Prominence of the pulmonary hila likely reflects bronchovascular crowding . The heart size is normal . No supine evidence for pneumothorax or effusion . Bony structures appear intact .
    OUTPUT:
    
Appropriately positioned endotracheal tube . No overt abnormalities in the chest .