Mid tracheostomy is done over which of the following anatomical landmarks?

Tracheostomy has also been divided into: A) High tracheostomy: Done above level of thyroid isthmus. Indication is ca larynx. B) Mid tracheostomy: It is the preferred one and done through II and III rings, division of isthmus. C) Low tracheostomy: Done below level of isthmus. Trachea is deep at this level and close to several large vessels. A mid tracheostomy is done through the II or III rings and would entail division of the thyroid isthmus (isthmus lies against II, III and IV tracheal rings) or its retraction upwards or downwards to expose this pa of trachea.