Ideal Endotracheal Tube Placement
The endotracheal tube tip should be positioned in the mid-trachea, approximately 3-5 cm above the carina, with the head and neck in neutral position. 1, 2
Anatomical Target Position
The optimal ETT tip position is 3-5 cm above the carina, which places it in the mid-tracheal region and minimizes risks of both endobronchial intubation and accidental extubation. 1, 3, 4
The tube must be positioned more than 2.5 cm from the carina (to avoid endobronchial intubation) and more than 3.5 cm below the vocal cords (to prevent accidental extubation). 4
Depth Marking at the Teeth/Lips
Standard Reference Points
For orotracheal intubation, traditional teaching suggests securing the tube at 23 cm at the teeth/gums for men and 21 cm for women. 2, 5
However, these fixed depths may not achieve ideal placement in all populations, particularly in shorter individuals or Asian populations where these reference marks resulted in inadequate positioning in 33% of cases. 5
Height-Based Formula (More Accurate)
- A more reliable approach uses the formula: (Height in cm ÷ 7) - 2.5 to determine optimal depth at the lips, as this correlates better with actual airway anatomy than fixed gender-based measurements. 6
Nasotracheal Intubation Depths
- For nasotracheal intubation, place the tube at 26 cm at the naris for women and 28 cm for men, which achieves adequate placement in 96-98% of patients. 7
Verification Methods (Two-Point Check)
After initial placement, a two-point verification is mandatory before inducing anesthesia: 1
Visual confirmation: Direct visualization of the tracheal tube passing through the vocal cords (via videolaryngoscopy) OR visualization of the tracheal lumen and carina (via flexible bronchoscopy). 1
Capnography: Continuous waveform capnography to exclude esophageal intubation (Class I, LOE C). 1, 8
Additional Confirmation
Once the bronchoscope is in the trachea, identify the carina before advancing the ETT to minimize misplacement risk. 1
Confirm the distance from the ETT tip to the carina is appropriate (3-5 cm) before removing the bronchoscope. 1
Obtain a chest X-ray when feasible to confirm proper positioning above the carina and rule out mainstem bronchial intubation. 8, 2
Alternative Placement Techniques
Tracheal Palpation Method
Tracheal palpation during tube advancement can improve placement accuracy, achieving correct positioning in 77% of cases compared to 61% with fixed depth measurements. 4
Place three fingers over the trachea from larynx to sternal notch; when the ETT tip is palpable at the sternal notch, this typically positions the tip approximately 4 cm above the carina. 4
Transillumination Method
- Using a flexible lighted stylet with maximal glow positioned at the sternal notch can consistently place the ETT tip 5 ± 1 cm from the carina. 3
Critical Pitfalls to Avoid
Never advance an airway exchange catheter beyond 25 cm in adults, as the distal tip must remain above the carina. 1
Maintain head and neck in neutral position after securing, as neck flexion can advance the tube 1-2 cm toward the carina, while extension can withdraw it. 8, 2
Re-verify tube position after securing, during transport, and with each patient movement, as displacement is the most common cause of unplanned extubation. 8, 9
If the patient deteriorates post-intubation, use the DOPE mnemonic: Displacement, Obstruction, Pneumothorax, Equipment failure. 8, 2
Avoid compressing the front and sides of the neck when securing the tube, as this impairs venous return from the brain. 8, 9