I am delighted with the interest our recent article1
sparked, and I thank the Editor-in-Chief for this opportunity to respond. I find common themes in all six letters. First, the subject of fiberoptic intubation is interesting and important. Second, more research is needed in this field. Third, several of the authors reported in one way or another in letters to the editor or clinical reports that endotracheal tubes stop at the arytenoid during fiberoptic intubation. Fourth, clinical observations in correspondences or clinical reports are good sources of ideas for rigorous scientific studies. Finally, for the record, Dana Johnson is not an M.D. yet. She is an outstanding medical student at the Carver College of Medicine at The University of Iowa (Iowa City, Iowa). I thank all of the authors for their insightful remarks and their interest in our article.
I agree with Drs. Ho and Karmakar that Cossham, in a letter to the editor in 1985, described the technique of inserting an endotracheal tube turned 90° counterclockwise over a gum elastic bougie in anesthetized patients.2
I did refer to Cossham’s letter in a previous article that described three cases of trauma to the airway by fiberoptic intubation.3
This was not the focus of the study and I certainly do not claim that I introduced this technique. The focus was to identify the structures that inhibit endotracheal tube advancement over a fiberoptic bronchoscope. I believe this goal was achieved. I apologize for not referring again to Dr. Cossham’s contribution.
Dr. Benumof is right, and I am right too. The corniculate cartilage is different from the arytenoid cartilage, although they are intimately related. According to Gray’s Anatomy
, the arytenoid cartilage is described in this fashion: “The apex of each cartilage is pointed, curved backward and medialward, and surmounted by a small conical, cartilaginous nodule, the corniculate cartilage” and also in this fashion: “The corniculate cartilages (cartilagines corniculatæ cartilages of Santorini
) are two small conical nodules consisting of yellow elastic cartilage, which articulate with the summits of the arytenoid cartilages and serve to prolong them backward and medialward.” Also according to Gray’s Anatomy
, another small cartilage, the cuneiform cartilage, also sits on the apex of the arytenoid cartilage.4
Both corniculate and cuneiform cartilages may or may not be present in humans. The arytenoid is the one that dislocates after traumatic intubations, not the corniculate or the cuneiform. In the medical community, the term arytenoid
is the one in common use and refers to the arytenoid complex, which encompasses all three structures. When the progress of the endotracheal tube is inhibited by the arytenoid cartilage, the tip of the tube may be stopped at the top of the arytenoids where the corniculate and the cuneiform cartilages are located, or it may reach all the way to the posterolateral aspect of the arytenoid cartilage at the cricoarytenoid junction, as is well illustrated in figure 1A of our article.1
I am aware of the remark of Schwartz et al.5
in a letter to the editor in 1989, and I apologize for not referring to it.
Dr. Asai, I read your article, Asai et al.
as well as your many other writings on fiberoptic intubation. In your article, you used two fiberoptic bronchoscopes simultaneously, as I did in my research,1
one inserted orally and the other inserted through the nose. Having said that, I stand behind my statement that “our study is the first to provide pictorial evidence of the laryngeal structures that obstruct the passage of the [endotracheal tube] during fiberoptic intubation.” In your article, you report that in 2 of 10 patients, the arytenoid cartilage stopped the advancement of the endotracheal tube. This is a perfectly valid clinical observation that was not supported by statistical analysis. I do agree that during the process of threading the tube over a bronchoscope, it is possible for the tube to enter the esophagus, although I did not make this observation in clinical practice or research.
In the article, I studied only oral fiberoptic intubation. I did not study nasal fiberoptic intubation. I agree with Drs. Wheeler and Dsida that the dynamics of threading the endotracheal tube are different in both types of intubations. With regard to oral fiberoptic intubation, the dynamics and the motility of the larynx and threading the endotracheal tube are widely variable between awake and anesthetized patients, let alone adding a plastic static human mannequin model into the comparison. Therefore, comparisons between a success rate of 298 in 300 in your study in threading the endotracheal tube in anesthetized patients7
and my success rate (50%) in awake patients should not be made, because they are two different clinical situations.
In Aoyama et al.
you made a valid clinical observation of the endotracheal tube stopping at the arytenoid cartilage. I did not encounter significant difficulties in determining the position of the fiberscope in relation to the arytenoids because, as shown in the pictures, the nasal fiberscope came very close to the oral fiberscope and the laryngeal structures. As you and Dr. Wheeler mention in your letters, there are many methods to facilitate successful threading of the endotracheal tube over the fiberscope.
Mazen A. Maktabi, M.D.
The University of Iowa, Iowa City, Iowa. firstname.lastname@example.org
1. Johnson D, From A, From RP, Smith R, Maktabi MA: Endoscopic study of laryngeal structures that obstruct smooth threading of the endotracheal tube during transoral fiberoptic intubation. Anesthesiology 2005; 102:910–4
2. Cossham PS: Difficult intubation (letter). Br J Anaesth 1985; 57:239
3. Maktabi MA, From RP, Hoffman H, Funk G: Trauma to the larynx during awake fiberoptic intubation. Anesth Analg 2002; 95:1112–4
4. Gray H: Anatomy of the Human Body. Philadelphia, Lea & Febiger, 1918
5. Schwartz D, Johnson C, Roberts J: A maneuver to facilitate flexible fiberoptic intubation (letter). Anesthesiology 1989; 71:470–1
6. Asai T, Murao K, Johmura S, Shingu K: Effect of cricoid pressure on the ease of fibrescope-aided tracheal intubation. Anaesthesia 2002; 57:909–13
7. Wheeler M, Roth AG, Dsida RM, Rae B, Seshadri R, Sullivan CL, Heffner CL, Cote CJ: Teaching residents pediatric fiberoptic intubation of the trachea: Traditional fiberscope with an eyepiece versus a video-assisted technique using a fiberscope with an integrated camera. Anesthesiology 2004; 101:842–6
8. Aoyama K, Takenaka I, Sata T, Shigematsu A: Use of the fiberscope-video camera system for difficult tracheal intubation. Br J Anaesth 1996; 77:662–4
© 2006 American Society of Anesthesiologists, Inc.