Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: A portable frontal chest radiograph demonstrates intact sternal wires , a valvular prosthesis , tracheostomy tube terminating in the upper trachea , and right subclavian central catheter terminating in the right atrium , all unchanged . There are low lung volumes resulting in exaggeration of the cardiac silhouette and bronchovascular crowding . Even allowing for this , there is at least mild to moderate cardiomegaly . Mild pulmonary edema is improved compared to chest radiograph from the day prior . Retrocardiac opacity may be due to left lower lobe volume loss , but superimposed infection can not be excluded . This is similar in appearance . Likely small left pleural effusion . No appreciable pneumothorax .
    OUTPUT:
    
1 . Improved pulmonary edema , now mild . Unchanged likely small left pleural effusion . 2 . Low lung volumes . Retrocardiac opacity which is likely due to left lower lobe volume loss , but superimposed infection can not be excluded in the absence of a lateral view , as before .