patient positioning in ion

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3 2 2 A N NA LS O F E M E RG E NC Y M E DI C IN E 4 1 :3 MARCH 2003

A I R W A Y / O R I G I N A L R E S E A R C H

Richard M. Levitan, MD

C. Crawford Mechem, MD

E. Andrew Ochroch, MD

Frances S. Shofer, PhD

Judd E. Hollander, MD

From the Departments ofEmergency Medicine (Levitan,Mechem, Shofer, Hollander)and Anesthesiology (Ochroch),University of PennsylvaniaSchool of Medicine, Philadel-

phia, PA.

Copyright 2003 by the American

College of Emergency Physicians.

0196-0644/2003/$30.00 + 0

doi:10.1067/mem.2003.87

Head-Elevated Laryngoscopy Position:Improving Laryngeal Exposure DuringLaryngoscopy by Increasing Head Elevation

See editorial, p. 338.

Study objective: The objective of this study was to determine the effect of increas-

ing head elevation and neck flexion on the quality of laryngeal view during laryn-

goscopy.

Methods: Laryngoscopy with a straight blade was performed on 7 fresh human

cadavers. Laryngeal views were recorded with the direct laryngoscopy video system,

and the laryngoscopy angle was measured throughout the procedure with an angle

finder attached to the handle of the laryngoscope. Each cadaver had laryngoscopy

initiated with the head lying flat on the table and with atlanto-occipital extension. The

head was then progressively elevated as much as possible (the head-elevated laryn-

goscopy position), increasing neck flexion and the laryngoscopy angle. Three physi-

cians blinded to the laryngoscopy angle graded the quality of laryngeal view using

the percentage of glottic opening (POGO) score.

Results: The laryngoscopy angle ranged from a mean of 328 (1 SD) with the head

flat on the table to a mean of 678 with the head-elevated laryngoscopy position.

The mean midposition laryngoscopy angle was 496. Comparing the 3 positions,

mean POGO scores1 SD significantly increased from 31%10% (flat position) to

64%12% (midposition) to 87%13% (head-elevated laryngoscopy position). Both the

midposition and the head-elevated laryngoscopy position compared with the flat

position were statistically significant at a Pvalue of less than .0001. The midposition

also differed significantly from the head-elevated laryngoscopy position (P


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I M P R O V I N G L A R Y N G E A L E X P O S U R E B Y I N C R E A S I N G

H E A D E L E V A T I O N

Levitan et al

MARCH 2003 4 1 :3 A N NA LS O F E M E RG E NC Y M E DI C IN E 3 2 3

I N T R O D U C T I O N

The importance of proper head and neck positioning

for optimizing laryngeal view during laryngoscopy has

been recognized since the procedure was first described

by Kirstein in 1895.1 Reference textbooks routinely

emphasize slight elevation of the head, extreme atlanto-

occipital extension, and lifting the handle of the laryn-

goscope in a 45direction.2-4

Direct laryngoscopy is the mainstay of emergency air-

way management, and despite the proliferation of diffi-

cult airway devices, alternative methods of intubation

are used extremely infrequently in all settings.5-12

Whether in the emergency department or in the operat-

ing room, there is a large discrepancy between the inci-

dence of difficult laryngoscopy (ie, multiple attempts or

poor laryngeal view), which ranges from 5% and 18%,

and the rate of failed laryngoscopy, which ranges from

less than 0.4% in the ED to 0.05% in the operating

room.5-13 In most instances, difficult laryngoscopy cor-

relates with poor laryngeal exposure.14,15 A study of

nearly 1,200 cases in the operating room identified

patient repositioning among the most common means of

facilitating intubation after an initial failed laryngoscopy

but did not define specific positioning changes.11

The assumptions regarding optimal positioning for

laryngoscopy have historically received little scientific

scrutiny.16,17 Two recent studies have questioned

standard practice regarding head and neck positioning

but seemingly came to different conclusions, with one

suggesting that increasing neck flexion was beneficial,

and the other concluding there was little benefit to mild

head elevation (and neck flexion) over simple exten-

sion.16,17 Neither of these studies used direct laryn-

goscopy imaging to dynamically record laryngeal view

and instead relied on estimations of transiently ob-

served laryngeal view at different positions, each using

a nonvalidated system of grading laryngeal view. Each

also had other issues that potentially limit the value of

their conclusions. One study used a curved blade, intro-

ducing the significant (and unmeasured) variable of

how the tip of the blade interacts with the hyoepiglottic

ligament and vallecula because minor changes in force

and direction at this location can markedly alter laryn-

geal exposure. The other study did not standardize

positioning through measurements between patients or

in any way measure head elevation or laryngoscopy

angle in the different positions.

The authors prior research has combined the use of

the direct laryngoscopy video system with a validated

means of assessing recorded laryngeal images (ie, the

percentage of glottic opening [POGO] score).18-24

Through prior video recordings of laryngoscopy and

our own clinical practice, we had anecdotal evidence

suggesting that increasing head elevation was a simple,

effective, and easily applied means of improving laryn-

geal exposure.

This study was designed to apply laryngeal imaging

and POGO scoring to objectively assess the effect of

dynamically increasing head elevation and associated

neck flexion on the quality of laryngeal view. Quanti-

fying the amount of head elevation is difficult to dy-

namically measure, and a specific amount of head eleva-

tion can have greater or less effect on resultant neck

flexion depending on a patients body habitus. Lifting

the patients head, however, also changes the directional

force along the laryngoscope handle, as well as the oper-

ators angle of view down the lumen of the blade. This

laryngoscopy angle can be readily measured with an

angle finder and can serve as a means of quantifying the

change in position resulting from head elevation.

M A T E R I A L S A N D M E T H O D S

The study was performed on 7 fresh human cadavers, 4

male and 3 female, at the medical school morgue at the

University of Pennsylvania School of Medicine. Laryngo-

scopy was performed with a Henderson laryngoscope

blade (Karl Storz Endoscopy, Inc., Culver City, CA).25

Like the Miller blade, the Henderson blade is a straight

blade with a narrow flange height, but it has a slightly

different-shaped lumen and a completely straight visi-

ble distal tip (Figure 1).26 The upturned tip of the

Miller blade or any curved blade design could poten-

tially cause a discrepancy between the laryngoscopy

angle (as measured and defined below) and the opera-


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Levitan et al

3 2 4 A N NA L S OF E M E RG E NC Y M E DI C IN E 4 1: 3 MARCH 2003

was affixed on the handle, the resultant angle on the

angle finder correlated with the angle of the laryngo-

scope blade relative to the patient. For example, if the

blade was oriented parallel to both the floor and the

long axis of the patient (with the handle pointing

straight up toward the ceiling), this would represent a

laryngoscopy angle of 0. If the blade was positioned

pointing vertically downward and perpendicular to

both the floor and the long axis of the patient (with the

handle now parallel to the patient), this would repre-

sent a laryngoscopy angle of 90.

Laryngoscopy was initiated with the head flat on the

table, with the occiput resting on the table and the head

extended at the atlanto-occipital joint (Figure 2). The

head was then progressively lifted from the table to a

height as high as possible (by the laryngoscopists right

hand), which simultaneously increased the degree of

neck flexion and the laryngoscopy angle displayed on

the angle finder (Figure 3).

tors actual angle of laryngeal view down the lumen of

the blade.27

The laryngoscopy angle was measured with a com-

mercially available angle finder obtained at a local hard-

ware store (Home Depot, Inc., King of Prussia, PA),

which was attached lengthwise to the laryngoscope

handle with plastic cable ties (Figures 2 and 3). Because

of the perpendicular position of the straight Henderson

blade to the handle and the manner that the angle finder

Figure 1.The Henderson straight laryngoscope blade (Karl StorzEndoscopy, Inc.). The blade is straight along its entire length,has a relatively small flange height, and has a visible distal

tip.

Figure 2.Laryngoscopy with the head flat on the table with an angle

finder attached lengthwise to the laryngoscope handle. Thelaryngoscope angle is approximately 40. Inset is the view ofthe larynx as displayed by the direct laryngoscopy video sys-tem worn by the laryngoscopist. The POGO score is approxi-mately 30%.

Figure 3.Laryngoscopy with the head fully elevated (ie, the head-ele-vated laryngoscopy position). The laryngoscopist is using theright hand to elevate the head. The laryngoscopy angle isapproximately 80, and the POGO score in the inset isapproximately 90%.


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Levitan et al


The laryngeal view was imaged continuously by

using the Airway Cam direct laryngoscopy video sys-

tem (Airway Cam Technologies, Inc., Wayne, PA).19

The direct laryngoscopy video system uses a head-

mounted miniature video camera that is aligned with

the line of sight of the laryngoscopists dominant pupil.

Video recording was done with a Sony GVD-300 (Sony

Corporation, Tokyo, Japan) digital videocassette re-

corder, capturing 30 frames per second. In addition to

the video recordings made with the direct laryngo-

scopy video system, a Sony DCR-PC1 (Sony Corpora-

tion) digital camcorder was simultaneously operated

by an assistant to record the laryngoscopy angle as seen

from a position perpendicular to the patient. The video

recordings of laryngeal view and the angle finder were

synchronized and superimposed with Adobe Premier

6.0 video editing software (Adobe Systems, Inc., Seattle,

WA; Figures 2 and 3).

The synchronized video clips were reviewed by 1 of

the authors (RML), and laryngoscopy angles were

recorded in 3 positions on each patient: head flat on the

table, full elevation, and a midposition that was selected

by observing the range of head elevation on the video-

tapes for each cadaver. Full elevation position was the

greatest amount of head elevation and greatest amount

of neck flexion achievable in each cadaver. The laryn-

geal views at the 3 positions were graded by 2 emergency

physicians (CCM, JEH) and 1 anesthesiologist (EAO)

using the POGO score.20,21The 3 physicians were

blinded to the laryngoscopy angle associated with each

laryngeal view, as well as to each others POGO scores.

The POGO score describes how much of the glottic

opening is visible; a 100% POGO score includes visual-

ization of the entire glottic opening from the anterior

commissure of the vocal cords to the interarytenoid

notch (Figure 4). A POGO score of 0% corresponds

with no visualization of laryngeal structures (ie, epi-

glottis or tongue-only views). The POGO score has

been shown to have excellent intrarater and interrater

reliability and to correlate with success of intubation, as

well as with need for rescue intubation devices.20,21,24

POGO scores were assigned to each cadaver at 3 posi-

tions from the videotape recordings: head flat on the

table, midposition, and full elevation. A 3-way analysis

of variance in repeated measures (1 observation per

cell) was used where the 2 repeated measures were rater

Figure 4.POGO score. Full visualization of the glottic opening fromthe anterior commissure to the interarytenoid notch equals100%. When no portion of the glottis is seen (ie, epiglottis ortongue-only views), the POGO score equals 0%. POGO scor-ing does not distinguish between these 2 situations.

Figure 5.Mean laryngoscopy angles at 3 different head positions in 7

cadavers. The midposition was determined by reviewingvideotaped images of laryngoscopy from a perspective per-pendicular to the patient. Bars represent mean1 SD.

100

80

60

40

20

0

Angleo

flarangoscopy

Head flat Mid-position Full elevation


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Levitan et al


Comparing the 3 positions, POGO scores signifi-

cantly increased from a meanSD of 31%10% (flat

position) to 64%12% (midposition) to 87%13%

(head-elevated laryngoscopy position; Figure 6). Both

the midposition and the head-elevated laryngoscopy

position compared with the flat position were statisti-

cally significant at a P value of less than .0001. The mid-

position also differed significantly from the head-ele-

vated laryngoscopy position (P


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Levitan et al


Hochman et al16 studied the effects of straight laryn-

goscope blade size, as well as head and neck positioning,

on the force required for optimal laryngeal exposure.

They concluded that increasing head elevation and

neck flexion increased the incidence of full laryngeal

exposure with less required force. Hochman et al char-

acterized the position that optimized laryngeal expo-

sure as flexion-flexion, referring to both atlanto-

occipital flexion and cervicothoracic vertebrae flexion.

An analysis of their photographs, however, suggests

that the atlanto-occipital joint is not truly flexed (ie, the

laryngoscopy angle is not >90). In our study, the laryn-

goscopy angle was always less than 90, even at full

head elevation. For this reason and also because head

elevated is a simpler term to describe the primary

movement, we believe that head-elevated laryn-

goscopy position is a better term for this type of posi-

tioning than flexion-flexion.

Our study has several limitations; we had a small

sample size, and all laryngoscopies were performed by

one laryngoscopist. We only studied laryngoscopy with

one blade design, and our results might not be transfer-

able to more commonly used blades. Although we be-

lieve that fresh cadavers approximate the mechanical

response to laryngoscopy in living patients, there might

have been unrecognized different responses to tongue

compression or other aspects of laryngoscopy that

might have affected our results. There is stress relax-

ation of the pharyngeal tissues and tongue during

laryngoscopy in live patients, and this might be differ-

ent than the response in cadavers.30We performed

laryngoscopy repeatedly to minimize the effect of

sequence on the results and did not observe significant

differences between laryngeal views at various posi-

tions going up versus going down, but this was not

specifically measured.

Our results focused on increasing glottic exposure,

but full exposure of the glottis is not required for intu-

bation, and the relevance of this degree of exposure for

intubation, particularly anterior glottic exposure, is

unknown. A prior study of nearly 6,000 patients found

that increasing POGO scores by greater than 25% is

clinically significant and that there is correlation be-

tween decreased POGO scores and the number of intu-

bation attempts, as well as the need for rescue intuba-

tion devices.24 It is unclear from this limited study how

Figure 7.Drawings of proper positioning. A, Normal recumbency onthe table with a pillow supporting the head. The larynx canbe directly examined in this position, but a better position isobtainable. B, Head is raised to proper position with the head

flexed. Muscles of the front of neck are relaxed, and exposureof the larynx is thus rendered easier. For most endoscopicwork, a certain amount of extension is desired, but the eleva-tion is the important thing. C, With the neck being main-tained in position B, the desired amount of extension of thehead is obtained by a movement limited to the occipito-atloidarticulation by the assistants hand placed, as shown by the

arrow (in B). Overextension is to be avoided. D, Faulty posi-tion. Reprinted with permission from Jackson C, Jackson CL.Bronchoscopy, Esophagoscopy and Gastroscopy: AManual of Peroral Endoscopy and Laryngeal Surgery.Philadelphia, PA: WB Saunders Company; 1934:85-105.38

Normal recumbency

Raised flexed

Raised, extendedCorrect

Faulty

HBHB

Occipito-alloidjoint

Chest heavedSpine arched

A

B

C

D


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Levitan et al


issues facing patients who require emergency intuba-

tion.5,36We believe that the easiest, fastest, and most

effective modification to improve view is external

laryngeal manipulation.22 For patients in whom neck

movement is not contraindicated, the head-elevated

laryngoscopy position is a second modification that can

be easily performed during initial laryngoscopy efforts

if the laryngeal view remains inadequate. The simplest

way to achieve the head-elevated laryngoscopy position

is for the laryngoscopist to directly lift the patients head

with his or her right hand. The right hand must be re-

leased to pass the tracheal tube, but for patients of normal

dimensions, suspending the head with the laryngo-

scope only for a brief moment is not difficult. In situ-

ations of extreme obesity, effective head elevation can-

effective the head-elevated laryngoscopy position

would be in instances when it is truly needed (ie, when

initial POGO scores are 0% or otherwise very low). We

believe that the technique improves the view across the

entire spectrum of laryngeal visualization, but we did

not have enough cases of poor initial view to prove this

in the present study.

Finally, although we believe that the head-elevated

laryngoscopy position improves laryngeal view, the

study only used cadavers, and the safety of this tech-

nique in living patients was not assessed. Obviously,

aggressive manipulation of the neck, even the standard

intubating position, is contraindicated in instances of

potential or existent cervical spine injury or pathol-

ogy.31,32

Ironically, there has been one case report of emer-

gency intubation with extreme flexion positioning on a

patient with anklylosing spondylitis and fixed flexion

of the cervical spine.33 Mindful of the patients prepro-

cedure cervical spine position, the clinician lowered the

head of the bed into the Trendelenburg position and

supported the patients head with a pillow; the resultant

laryngoscopy angle was almost 90, and the vocal cords

were completely exposed.33

There is evidence from radiographic studies and

clinical reports that increasing head elevation might be

safer than increasing atlanto-occipital extension in sit-

uations of poor laryngeal exposure. Neurologic injury

related to overaggressive head and neck extension dur-

ing laryngoscopy has been reported, specifically central

cord syndrome.34 Radiographic analysis has shown that

extension from C1-C4 is near maximal in the standard

intubating position, when the lower spine is relatively

straight.35 For this reason, it has been suggested that if

standard positioning is to be modified, any additional

extension should be avoided, and instead additional

flexion (ie, head elevation) should be attempted.35

Modifications of laryngoscopy techniques that can

increase first-pass intubation success are critical in the

emergency setting. Simple maneuvers that can improve

laryngeal view without requiring special tools, exten-

sive training, or expense are particularly valuable given

the reliance in the ED on laryngoscopy and the clinical

Figure 8.Achieving the head-elevated laryngoscopy position in a mor-bidly obese patient requires massive amounts of supportunder the head and shoulders. Used by permission from

Airway Cam Technologies, Inc., Wayne, PA.


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Levitan et al


not be done singlehandedly by the laryngoscopist and

instead requires massive amounts of support placed

under the shoulders, as well as the head (Figure 8).2,37

Alternatively, as demonstrated by Hochman et al,16 the

patients head can be supported by the laryngoscopists

torso leaning inward, but with a standard stretcher, this

requires the patients head to be positioned at the ex-

treme edge of the bed. The head-elevated laryngoscopy

position can also be easily achieved with an assistant,

which was the technique advocated by Jackson and

Jackson.38We believe this is best accomplished by the

assistant being at a position near the head of the bed,

crouching down until his or her shoulders are at the

level of the patient, and then lifting with both arms to

support the patients head and shoulders.

This study demonstrates significantly improved

POGO scores on fresh cadavers by using the head-

elevated laryngoscopy position. We have had anecdotal

success with the head-elevated laryngoscopy position

in our ED during difficult laryngoscopies and believe

the technique warrants prospective study with laryngo-

scopic imaging in living patients. Further study is

needed to define its utility in cases of very poor initial

laryngeal view, as well as to prove its safety and efficacy

in the emergency setting.

We thank J. Dwayne Hallman, BS, Anatomy Morgue Technician,

and Dr. Paul Teresi, MD, Anatomy Morgue Director, each of the

University of Pennsylvania School of Medicine, for their assistance

with this project. Boaz Rosenblatt, MD, and Nancy Sun, MD, each

assisted with the video recordings.

Author contributions: RML designed the study and performed all the

laryngoscopies. CCM and EAO videotaped and provided assistance

in the cadaver laboratories. CCM, EAO, and JEH performed POGO

scoring of the laryngeal images. JEH and FSS were responsible for

revising the paper, as well as the statistical analysis. RML takes pri-

mary responsibility for the paper as a whole.Received for publication February 22, 2002. Revisions received

August 2, 2002, and August 20, 2002. Accepted for publication

August 26, 2002.

The authors report this study did not receive any outside funding or

support.

Dr. Levitan is the patent holder on the direct laryngoscopy video

system used for videographic imaging of laryngoscopy in this study.

He is also a principal owner of Airway Cam Technologies, Inc.,

Wayne, PA, which produces and sells the imaging system.

Reprints not available from the authors.

Address for correspondence: Richard M. Levitan, MD, Department

of Emergency Medicine, Hospital of the University of Pennsylvania,

3400 Spruce Street, Philadelphia PA 19104; 215-662-7260; E-mail

[email protected].

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