In emergency tracheostomy following structures are damaged except:

Structures which lie below the midline viz. isthmus of thyroid and thyroid ima aery can be damaged in emergency tracheostomy. Inferior thyroid veins emerge at the lower border of the isthmus form a plexus in front of the trachea and drains into brachiocephalic vein can be damaged during tracheostomy but inferior thyroid aery, a branch of thyrocervical trunk of subclan aery lies laterally away from midline and can thus escape injury.