Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Portable AP upright chest film ___ at 06 :04 is submitted
    OUTPUT:
    
Lung volumes remain slightly low . Streaky opacities at the left base and at the medial right base likely reflect atelectasis , although an early infectious process can not be excluded . No evidence of pulmonary edema . No pneumothorax . Overall cardiac and mediastinal contours are stable . Slight interval improvement in the area of focal tracheal narrowing . No large effusions .