Why posterior cricoartenoid is known as safety muscle of larynx?

Why posterior cricoartenoid is known as safety muscle of larynx ?

Posterior cricoarytenoid is the only abductor of Vocal cords.Therefore is important for maintaining the airway patency during breathing.Therefore it is called the safety muscle of larynx.The nerve supply is Recurrent laryngeal nerve.Any injury to RLN will cause medialisation of Vocal cord.And in case there is a bilateral RLN injury both vocal cords will be in the medial position and the patient will need immediate tracheostomy to maintain breathing.

It is the only abductor of vocal cords. Abducted position facilitates passage for breathing while adducted position of cords is important for voice production. Thus if posterior cricoarytenoid is damaged, vocal cords are approximated and breathing suffers.