Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: The left hemidiaphragm continues to be elevated . However , there is some increased volume loss in the left lower lobe and a small left effusion . There is improved aeration in the right upper lobe , but some patchy areas of alveolar infiltrate have developed bilaterally . It is unclear if this is due to pulmonary edema or if an infectious process is present . Tracheostomy tube is unchanged . The low lung volume slightly limits this examination . It is unclear how much of these changes are actually due to low lung volumes .
    OUTPUT:
    
Low lung volumes are slightly worse in appearance on the left . The alveolar infiltrates could be due to asymmetric presentation of pulmonary edema .