Ideal endotracheal tube position is having the tube tip in the mid-trachea. If the ETT is too shallow it can result it accidental extubation. If it is too deep it can go endobronchial, which could result in one-lung ventilation, barotrauma and hypoxia. X-rays and bronchoscopy are the gold standards for confirming correct position. In theatres and in emergency medicine we initially rely on a simple method where we measure the tube at the incisors. 23 cm is considered the ideal position for men and 21 cm for women.
The paper in Can J Anesth describe a technique that relies on identifying the correct tube position by palpating trachea at three points. Index finger over the cricothyroid membrane, middle finger over the trachea and the ring finger at the sternal notch. After passing the vocal chords, the tube is slowly advanced down the trachea until it is felt at the sternal notch. The authors stress the importance of feeling the tube passing each of the fingers in turn. Sometimes the tube gets caught in the larynx, moving the entire trachea which could be misinterpreted as sternal notch position of the tube.
In this study the standard tube measurement method (MM) was compared against the tracheal palpation method. Both methods were compared to a gold standard bronchoscopy measurement. Correct tube position was defined as a tube tip that was > 2,5 cm from the carina and > 3,5 cm from the vocal chords.
Using the tracheal palpation method the ETT was correctly placed in 77% of patients.Using the conventional tube measurement method, only 61% were correctly placed.
The authors suggest tube placements will become even more ideal if the tube is retracted one cm after palpating the tip in the sternal notch.
Verifying the correct tube depth through tracheal palpation seems to work. I know this has been shown before in neonatal intubations, where even minor tube dislocations can be disastrous. Cliff Reid wrote about it here.
Paper lives here:
Can J Anaesth. 2014 Mar;61(3):229-34. doi: 10.1007/s12630-013-0079-4. Epub 2013 Nov 21. Tracheal palpation to assess endotracheal tube depth: an exploratory study.McKay WP1, Klonarakis J, Pelivanov V, O’Brien JM, Plewes C.