Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Portable upright radiograph of the chest demonstrates well expanded and clear lungs . The cardiomediastinal and hilar contours are unremarkable . There is no pneumothorax , pleural effusion , or opacity . Pneumomediastinum is not apparent on this radiograph .
    OUTPUT:
    
Normal chest x-ray examination . No evidence of pneumomediastinum .