CE - LETTER TO THE EDITOR

The factors affecting success rate of emergency intubation:author’s reply

James Matthew Dargin • Lillian Liang Emlet •

Francis Xavier Guyette

Received: 20 June 2013 / Accepted: 21 August 2013 / Published online: 29 September 2013

� SIMI 2013

Dear Editor,

We thank Dr. Ding and colleagues [1] for their interest in

our study, ‘‘The effect of body mass index on intubation

success rates and complications during emergency airway

management’’ [2]. We agree that the aligning of the

external auditory canal parallel with the sternal notch in the

‘‘ramped’’ position significantly improves the laryngo-

scopic view when compared to the ‘‘sniff’’ position in

morbidly obese patients [3]. However, Critical Care Med-

icine fellows, who performed the vast majority of intuba-

tions in our study, receive extensive training in

management of the difficult airway, and are instructed to

use the ramped position for morbidly obese patients. We

suspect that similar laryngoscopy grades among different

BMI categories were achieved, in part, through proper

positioning. However, we do not have data to support or

refute this hypothesis, and documentation of such positions

would be difficult to accurately record during emergent

inpatient airway management.

Dr. Ding and colleagues point out that the laryngoscopic

view generally correlates with intubation success. How-

ever, difficult laryngoscopy and difficult intubation are not

necessarily equivalent. For example, a patient with a grade

I laryngoscopic view may be virtually impossible to intu-

bate orally due to subglottic stenosis. Conversely, a patient

with a grade III view may be easily intubated on the first

attempt using a tracheal tube introducer (bougie). On fur-

ther analysis of our data, we found that 280 obese or

morbidly obese patients had a grade I or II view, and 19

(7 %) of these patients required more than 2 intubation

attempts. We used a malleable stylet inserted into the tra-

cheal tube for all intubations involving direct laryngoscopy

in our study, which is recommended for emergency intu-

bations [4]. With regard to the use of fiberoptic intubation,

11 out of 77 patients with a body mass index [40 kg/m2

required the use of this technique. Eight of 11 (73 %) of

these patients required fiberoptic intubation on the first

attempt and 3 others required this method as a rescue

technique. As summarized in Table 2, an ‘‘awake tech-

nique’’ was used on the first attempt approximately twice

as frequently in morbidly obese patients (10 %) than lean

(4 %), overweight (4 %), or obese patients (6 %).

As pointed out, observational studies are potentially

subject to bias and we did emphasize this limitation in our

discussion. Using standard logistic regression techniques,

we attempted to control for other predictors of difficult

intubation in our analysis. We hypothesize that obesity,

but not morbid obesity, predicted difficult intubation

because morbidly obese patients are perceived as difficult

and treated as such; whereas obese patients are not per-

ceived as difficult, and are treated with less attentiveness

when compared to the morbidly obese. However, our

findings may be affected by other confounding factors or

the small sample size of morbidly obese patients. As

pointed out, all of the cricothyrotomies occurred in lean

patients. However, we only observed four surgical airways

in more than 1,000 patients. Thus, the low incidence of

this event makes it difficult to draw any conclusions about

this finding.

Lastly, we would like to address the comments

regarding the use of neuromuscular blocking agents. It is

difficult to assess the effect of neuromuscular blocking

agents on intubation success rates in our study, as the

morbidly obese group received these medications less

J. M. Dargin (&) � L. L. Emlet � F. X. Guyette

Burlington, USA

e-mail: James.M.Dargin@lahey.org

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Intern Emerg Med (2014) 9:353–354

DOI 10.1007/s11739-013-0992-0

frequently primarily due to anticipated difficulty, which is

in keeping with standard anesthetic and emergency airway

teaching [5]. Thus, such an analysis would inherently be

subject to bias. We would like to note that, to our

knowledge, there are no randomized, controlled trials

examining intubation success rates during emergency

airway management with and without the use of neuro-

muscular blocking agents. Based on observational studies,

intubating success rates appear to be similar or better with

the use of neuromuscular blocking agents [6]. As a result,

neuromuscular blocking agents are commonly used for

emergency airway management, as Dr. Ding and col-

leagues point out. Thus, observational studies, despite

their intrinsic limitations, provide important information

for clinical practice, particularly when randomized trials

are difficult or unethical to perform, as is often the case

during emergency airway management.

James M. Dargin, MD

Lillian L. Emlet, MD

Frank X. Guyette, MD

Conflict of interest None.

References

1. Ding X-L, Wang S-Y, Yang R-M, Xue F-S (2013) The factors

affecting success rate of emergency intubation. Intern Emerg Med.

doi:10.1007/s11739-013-0990-2

2. Dargin JM, Emlet LL, Guyette FX (2013) The effect of body mass

index on intubation success rates and complications during

emergency airway management. Intern Emerg Med 8(1):75–82

3. Collins JS, Lemmens HJ, Brodsky JB et al (2004) Laryngoscopy

and morbid obesity: a comparison of the ‘‘sniff’’ and ‘‘ramped’’

positions. Obes Surg 14:1171–1175

4. Levitan RM, Pisaturo JT, Kinkle WC, Butler K, Everett WW

(2006) Stylet bend angles and tracheal tube passage using straight-

to-cuff shape. Acad Emerg Med 13(12):1255–1258

5. Flint PW, Haughey BH, Lund VJ, Niparko JK, Richardson MA,

Robbins KT, Thomas JR (2010) Cummings Otolaryngology: Head

& Neck Surgery, 5th edn. In: Chapter 10: Surgical management of

the difficult adult airway. Mosby Elsevier. Philadelphia

6. Wilcox SR, Bittner EA, Elmer J et al (2012) Neuromuscular

blocking agent administration for emergent tracheal intubation is

associated with decreased prevalence of procedure-related com-

plications. Crit Care Med 40(6):1808–1813

354 Intern Emerg Med (2014) 9:353–354

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