Correspondence

Video on Orotracheal Intubation

N Engl J Med 2007; 357:619-621August 9, 2007

Article

To the Editor:

In the Video in Clinical Medicine about orotracheal intubation, presented by Kabrhel et al. (April 26 issue),1 the authors state that the “combination of flexion of the neck and extension of the head [the sniffing position] improves the alignment of the axes of the oral cavity, pharynx, and larynx, facilitating optimal visualization of the vocal cords.” This is an anatomical myth that is not supported by clinical evidence.2 In a randomized crossover study of 456 consecutive patients, Adnet et al.3 found no differences in glottic visualization by direct laryngoscopy or in the score on the intubation-difficulty scale between the use of simple head extension and routine sniffing position. Furthermore, in 11% of patients, glottic exposure was lessened with the use of the “three axes alignment.” However, a multivariable analysis showed that reduced neck mobility and obesity were independently related to improvement in the laryngoscopic view with the use of the sniffing position.3 These results are consistent with studies of other populations4 and with anatomical studies involving magnetic resonance imaging.5 In conclusion, routine use of the sniffing position should not be a standard procedure in orotracheal intubation.

David A. Rincón, M.D.
Universidad Nacional de Colombia, Bogotá 11001000, Colombia
darinconv@unal.edu.co

5 References

1
Kabrhel C, Thomsen TW, Setnik GS, Walls RM. Orotracheal intubation. N Engl J Med 2007;356:e15. [Erratum, N Engl J Med 2007;356:2228.]

2
Adnet F, Borron SW, Lapostolle F, Lapandry C. The three axis alignment theory and the “sniffing position”: perpetuation of an anatomic myth? Anesthesiology 1999;91:1964-1965
CrossRef | Web of Science | Medline

3
Adnet F, Baillard C, Borron SW, et al. Randomized study comparing the “sniffing position” with simple head extension for laryngoscopic view in elective surgery patients. Anesthesiology 2001;95:836-841
CrossRef | Web of Science | Medline

4
Collins JS, Lemmens HJM, Brodsky JB, Brock-Utne JG, Levitan RM. Laryngoscopy and morbid obesity: a comparison of the “sniff” and “ramped” positions. Obes Surg 2004;14:1171-1175
CrossRef | Web of Science | Medline

5
Adnet F, Borron SW, Dumas JL, Lapostolle F, Cupa M, Lapandry C. Study of the “sniffing position” by magnetic resonance imaging. Anesthesiology 2001;94:83-86
CrossRef | Web of Science | Medline

To the Editor:

In their video on orotracheal intubation, Kabrhel et al. suggest that neuromuscular-blocking agents and sedatives will “prevent the patient from vomiting.” Readers should not be comforted that the use of these agents will prevent emesis. Etomidate, the medication mentioned in the video, is known to be emetogenic and has been shown to be associated with emesis during intubation.1 In addition, we were disappointed that there was no mention of the difficult-airway algorithm of the American Society of Anesthesiologists, an evidence-based practice guideline on this important topic that has guided airway management for 15 years.2

Sachin Kheterpal, M.D.
George A. Mashour, M.D., Ph.D.
University of Michigan, Ann Arbor, MI 48109
sachinkh@med.umich.edu

2 References

1
Bozeman WP, Young S. Etomidate as a sole agent for endotracheal intubation in the prehospital air medical setting. Air Med J 2002;21:32-37
CrossRef | Medline

2
Practice guidelines for management of the difficult airway: an updated report by the American Society of Anesthesiologists Task Force on Management of the Difficult Airway. Anesthesiology 2003;98:1269-1277[Erratum, Anesthesiology 2004;101:565.]
CrossRef | Web of Science | Medline

To the Editor:

Kabrhel et al. recommend use of a carbon dioxide detector to confirm the placement of the endotracheal tube. Furthermore, they suggest that the device be used to detect carbon dioxide consistently within the first six breaths after intubation and during subsequent breaths. They caution that false negative results with regard to tube placement may occur in patients in cardiac arrest, in whom carbon dioxide may not be present in the lungs.

It would have been relevant to point out the possibility of color change in the device due to agents other than exhaled carbon dioxide. Gastric contents, mucus, and drugs such as epinephrine can cause false positive results.1,2 It is imperative that clinicians using these devices be aware of this limitation. One way to avoid this pitfall is to observe the change in color in the device with each breath. A false positive result causes a permanent color change in the device; hence, the color does not vary with ventilation.

Venkatesh Srinivasa, M.D.
VA Boston Healthcare System, West Roxbury, MA 02132
venkatesh.srinivasa@va.gov

Bhavani Shankar Kodali, M.D.
Brigham and Women's Hospital, Boston, MA 02115

2 References

1
Brackney SM, Bennett NP. Caution when using colorimetry to confirm endotracheal intubation. Anesth Analg 2007;104:738-739
CrossRef | Web of Science | Medline

2
Srinivasa V, Kodali BS. Caution when using colorimetry to confirm endotracheal intubation. Anesth Analg 2007;104:738-738
CrossRef | Web of Science | Medline

To the Editor:

The video on orotracheal intubation places special emphasis on the use of pressure on the cricoid cartilage during emergency intubation (the Sellick maneuver), even though this maneuver is not always used. The usefulness of cricoid pressure in preventing aspiration has never been proved, and there is ample literature on both sides of the issue. What is not in doubt is that abnormally applied cricoid pressure can lead to partial or complete obstruction of the airway, making ventilation and intubation difficult or impossible. Also not in doubt is the fact that very few practitioners know where the cricoid cartilage is and how to hold 30 N of pressure. One other indisputable fact is that aspiration, though potentially fatal, is very rare if intubation is performed correctly. Thus, I would recommend that the emphasis on the Sellick maneuver be completely removed from this video, since it is more likely to cause harm than good if the person performing the intubation is inexperienced.

Nir Hoftman, M.D.
University of California, Los Angeles, Los Angeles, CA 90049

Author/Editor Response

The concise format of procedural videos, such as ours, limits what can be addressed. Though the sniffing position is the most commonly recommended position to facilitate orotracheal intubation and is considered the standard of care,1 its usefulness has been debated. The crossover study cited by Dr. Rincón compared the sniffing position with head extension but not with neutral position.1 Considering the study design, it is somewhat misleading to focus only on the 11% of patients in whom neck extension alone provided better glottic exposure without mentioning the 18% of patients in whom the sniffing position provided a better view. Studies have demonstrated an improved laryngoscopic view with head elevation as compared with neutral position.2 However, we agree that for most patients, the benefit of the sniffing position is probably conferred by the head extension it provides. As such, we do not find a strong reason to abandon a long-standing practice, and we agree with Adnet et al.,1 who state that their study is “less an indictment of the sniffing position than reinforcement of the importance of head extension in all patients.”

We agree with Drs. Kheterpal and Mashour that the difficult-airway algorithm of the American Society of Anesthesiologists is a very useful guide. However, it is perhaps most applicable to the planning of operating-room cases and is less helpful when intubation is emergent or unavoidable. They are correct in stating that etomidate can cause emesis, but this is not an issue when neuromuscular-blocking agents are also used. Unfortunately, detailed discussions of the American Society of Anesthesiologists algorithm and pharmaceutical adjuncts were beyond the scope of our video. We also agree with Drs. Srinivasa and Kodali that during assessment of end-tidal carbon dioxide levels, the detector should be free of foreign material (e.g., vomit, mucus, or drugs) and that the color should vary during the respiratory cycle.

Regarding Dr. Hoftman's comments: we acknowledge in the text accompanying the video that cricoid pressure can distort the airway and that the benefit of decreased aspiration is theoretical. The maneuver is also frequently performed improperly. Although the evidence is mixed as to whether cricoid pressure improves or degrades intubating conditions, surveys show that it is almost universally performed,3 so we thought it best to describe the technique. No doubt, future studies will clarify the precise role, if any, for this maneuver.

Christopher Kabrhel, M.D.
Massachusetts General Hospital, Boston, MA 02114

Todd W. Thomsen, M.D.
Mount Auburn Hospital, Cambridge, MA 02138

Ron Walls, M.D.
Brigham and Women's Hospital, Boston, MA 02115

3 References

1
Adnet F, Baillard C, Borron SW, et al. Randomized study comparing the “sniffing position” with simple head extension for laryngoscopic view in elective surgery patients. Anesthesiology 2001;95:836-841
CrossRef | Web of Science | Medline

2
Levitan RM, Mechem CC, Ochroch EA, Shofer FS, Hollander JE. Head-elevated laryngoscopy position: improving laryngeal exposure during laryngoscopy by increasing head elevation. Ann Emerg Med 2003;41:322-330
CrossRef | Web of Science | Medline