Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: A single frontal view of the chest shows linear opacities at the bilateral bases , greater on the right than the left . These are stable from prior exams and most consistent with atelectasis or scarring . No new opacities identified . The lung volumes are low . There is no pulmonary edema , pleural effusion , or pneumothorax . The cardiomediastinal silhouette is normal . A tracheostomy tube is present approximately 4 cm from the carina .
    OUTPUT:
    
1 . No acute cardiopulmonary process . 2 . Stable bibasilar atelectasis or scarring .