To the Editor:—
Lenfant et al. 1are to be congratulated on their study comparing two techniques for retrograde orotracheal intubation using the cricothyroid approach in cadavers. Their modified technique is similar to that reported by Tobias,2although he used a fiberscope as a catheter through the endotracheal tube into the trachea before removing the guide wire.
The authors report 22 failures with the classic technique versus 8 with the modified technique. It is not clear whether esophageal intubation occurred in all of these cases or whether there was supraglottic placement in some. Also, there is no mention of the size or type of endotracheal tube used in the study.
It is crucial that the tip of the endotracheal tube is positioned beneath the vocal cords for subsequent successful passing of the catheter into the trachea. Although passing a thin catheter over the guide wire is easier, resistance may be encountered while advancing the endotracheal tube over the catheter, especially at the level of the glottis. Similar difficulty with the advancement of the endotracheal tube over a fiberscope3or a bougie4is well documented and is related to the size and type of endotracheal tube and the position of the bevel. It would be interesting to know the incidence of such “hanging-up” phenomenon and the requirement for any maneuver to overcome the same in the current study. It is important to understand the dynamics of failed retrograde intubations to improve the success rate.
The authors comment that the subcricoid approach may be more dangerous than the cricothyroid approach. Literature on the use of the subcricoid approach for retrograde intubation is sparse. Subcutaneous emphysema, minor skin bleeding, and incorrect positioning are the reported complications (10%) with percutaneous minitracheostomy using the subcricoid approach in 50 patients.5On the contrary, it is shown that retrograde intubation using the cricothyroid approach has more potential to cause vocal cord trauma than the subcricoid approach.6Various complications, including pneumomediastinum, have been reported after the cricothyroid approach.7The area from the cricoid cartilage to the lower border of the first ring of the trachea is devoid of major blood vessels or nerves,8whereas the cricothyroid membrane is crossed by the cricothyroid artery superiorly.9The subcricoid approach of retrograde intubation using the cricotracheal membrane seems relatively safe, with the advantage of improved success rate.6,8
Colchester General Hospital, United Kingdom. firstname.lastname@example.org