Bedside prediction of airway length in adults and children

Malpositioning of the endotracheal tube within the airway leads to serious complications such as endobronchial intubation. Prediction of the correct depth of an endotracheal tube is important and should be individualized. The manubriosternal joint (MSJ) is on the same horizontal plane with the tracheal carina. We compared the straight length from the upper incisor to the MSJ in the fully extended position (incisor-MSJ extension length) with the length from the upper incisor to the carina after intubation with a flexible fiberoptic bronchoscope through the endotracheal tube in the neutral position (incisor-carina neutral length).

One hundred adults and 50 children were studied. Induction of anesthesia was achieved with 1.5 mg/kg propofol and 0.6 mg/kg rocuronium IV. The incisor-MSJ extension length was measured after adequate mask ventilation. After intubation, the endotracheal tube was positioned properly at the upper incisor teeth, and the incisor-carina neutral length was measured with the fiberoptic bronchoscope at the carina.

The correlation between the incisor-MSJ extension length and the incisor-carina neutral length is significant (P < 0.001) in both adults and children. A formula for the regression line in adults (children) can be obtained as the incisor-carina neutral length (cm) = 0.868 (1.009) x the incisor-MSJ extension length (cm) + 4.260 (0.468) with a high coefficient of determination; r(2) = 0.88 (0.98).

The airway length from the upper incisor to the carina in the neutral position can be predicted by the straight length from the upper incisor to the MSJ in the fully extended position.