Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Single AP upright chest radiograph demonstrates normal heart size . Mediastinal and hilar contours are within normal limits . There is no pneumothorax , pleural effusion , or evidence of pulmonary edema . There is no visualized pneumomediastinum . Streaky opacity at the left lung base likely reflects atelectasis . Lucency projecting over the midline is likely sequela of a skin fold . No evidence of pneumomediastinum .
    OUTPUT:
    
No acute cardiopulmonary process .