This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Operative Surgery, Subject name: ENT
Tracheostomy opening is put on.....tracheal rings: 
Select and explain. 
A. 2-Jan, B. 3-Feb, C. 7-Apr, D. 6-May
B: 3-Feb
Answer: B: 3-Feb 
Explanation: Ans: b (2 - 3 rings) Ref:Dhingra, 3rd ed, p. 382 & 4"'ed, p. 292Tracheostomy: Making an opening in the anterior wall of trachea & converting it into a stoma on the skin surfaceTracheotomy: Means opening the trachea, a step in tracheostomy operationTracheostomy can be divided into 3 types:HighMidLowHigh tracheostomy:Above the level of thyroid isthmus(Isthmus lies against II. III. IV tracheal rings)It disrupts Is' ring of trachea- almost always avoided.Disadvantage: Perichondritis of cricoid cartilage, subglottic stenosisOnly indication: Carcinoma larynxMid tracheostomy:Done through 2nd or 3rd tracheal ringsPreferred approachLow tracheostomy:Below the level of isthmusDisadvantage: Trachea is close to major vessels at this level & may get injuredTracheostomy tube may impinge on suprasternal notch