Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Left - sided chest tube has apparently been modified since the earlier study . There is trace air visualized in the left hemithorax , similar to decreased . The degree of lung collapse appears on the whole improved although with persistent volume loss at the left lung base . The right lung remains clear . There is still moderate subcutaneous emphysema .
    OUTPUT:
    
Overall improvement in the degree of atelectasis following apparent revision of chest tube . Trace pneumothorax .