A 70 kg adult woman is intubated orally with a 7.0 mm internal diameter endotracheal tube. Using the standard formula based on tube internal diameter, the expected depth at the incisors for mid-tracheal placement is:
- A 14 cm
- B 18 cm
- C 21 cm ✓
- D 24 cm
Correct answer: C. 21 cm
Explanation
Oral endotracheal tube depth is estimated as three times the internal diameter in centimetres, giving 21 cm for a 7.0 mm tube in an adult female; adult males typically require 23 cm. The alternative weight-based estimate is 6 plus body weight in kilograms divided by 10. Fourteen centimetres would leave the cuff in the pharynx, 18 cm risks extubation or glottic placement, and 24 cm risks endobronchial intubation, usually right main bronchial.
Reference: Morgan and Mikhail's Clinical Anesthesiology, 7th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.