Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: The lungs are underinflated , resulting in crowding of the bronchovascular structures . The heart size is top normal . The hilar and mediastinal contours are within normal limits . No definite consolidation is seen . The central pulmonary vessels are prominent ; however , no overt edema is detected . There is no pneumothorax or pleural effusion .
    OUTPUT:
    
Study limited by poor inspiratory effort ; no acute intrathoracic process .