Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: The heart size is normal . The lungs are well expanded and clear . There is no evidence of pleural effusion or pneumothorax . The hilar and mediastinal contours are unremarkable . The visualized osseous structures are unremarkable .
    OUTPUT:
    
No acute cardiopulmonary process to explain patient 's low oxygen saturation .