Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Portable semi-erect chest film ___ at 04 :48 is submitted .
    OUTPUT:
    
Endotracheal tube and nasogastric tube are likely unchanged in position . There are patchy bibasilar opacities which are not significantly changed and may reflect bibasilar atelectasis , although pneumonia can not be excluded . A layering left effusion is again noted . No evidence of pulmonary edema . No large pneumothorax is seen , although the sensitivity to detect pneumothorax is diminished given semi-erect technique . Overall cardiac and mediastinal contours are stable .