Normal Endotracheal Tube Position on Chest Radiography
The endotracheal tube (ETT) is a critical airway device placed in intubated patients to maintain ventilation. Confirming correct tube tip position on chest radiograph is a fundamental task in the ICU and emergency settings. Malposition carries serious risks, including endobronchial intubation, atelectasis, barotrauma, or inadvertent extubation.
Normal Reference Values
| Location | Measurement |
|---|---|
| Normal Position | 3-5 cm above the carina |
Clinical Significance
The ETT tip should ideally lie 3–5 cm above the carina with the patient’s neck in neutral position. This range provides a safety margin accommodating head flexion (which advances the tube ~2 cm) and extension (which withdraws the tube ~2 cm). A tip positioned too low risks right mainstem bronchial intubation, causing left lung collapse and right lung overinflation. A tip positioned too high risks accidental extubation.
The carina is typically projected at the level of the T4–T6 vertebral bodies or the angle of Louis on frontal radiographs. However, the carina is not always directly visible; the tracheal bifurcation angle or the right and left mainstem bronchi serve as landmarks. Tube depth should be reassessed after any patient repositioning.
- Too low (<2 cm above carina): Risk of right mainstem intubation, left-sided atelectasis
- Too high (>6 cm above carina): Risk of inadvertent extubation, supraglottic placement
- Right mainstem intubation: Right upper lobe collapse risk due to occlusion of right upper lobe bronchus
- Post-repositioning malposition: Head flexion or rotation after confirmed placement
- Esophageal intubation: Tube lateral to tracheal air column or gastric distension
Reference: Kanzawa M, Hirai C, Morinaga Y et al. Primary submucosal nodular plasmacytoma of the stomach: a poorly recognized variant of gastric lymphoma. Diagn Pathol. 2013;8(1):30.
Imaging Notes
On portable anteroposterior (AP) chest radiography, assess ETT tip position with the patient’s neck in neutral alignment whenever possible. The tube tip appears as a radiodense line within the tracheal air column. Measure the distance from the tip to the carina in centimeters; the carina is identified at the tracheal bifurcation, often near the T4–T6 level. Note that AP projection and patient rotation can introduce parallax error, so correlation with clinical examination is always recommended.
Ensure the ETT cuff region (visible as a subtle focal tracheal widening) does not lie at or above the level of the vocal cords, and that no tracheal wall irregularity suggests overdistension. Repeat radiography is warranted after any tube advancement, withdrawal, or significant patient movement.