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42 Dicult Airway Management forENT Surgery forNon-anesthesiologists
497
nose, mouth, and neck should be immediately
apparent.
Patency of nares, polyps, or mass inside the
nasal cavity, nasal septum deviation should be
ruled out.
The adequate mouth opening of at least 2–3
large ngerbreadths between upper and lower
incisors in adults is desirable, with distance varies
from 4–6cm and gives an indication of temporomandibular joint (TMJ) mobility, also assess TMJ
for movement restriction as in ankylosis/brosis,
tumors, etc. Examination of the ability to protrude
the lower jaw beyond the upper incisors.
Teeth examination for prominent upper incisors, or overbite, can impose a limitation on the
alignment of oral or pharyngeal axes during
laryngoscopy, and especially in association with
a large base of the tongue, they can compound
the difculty during the direct laryngoscopy or
bag-mask ventilation.
Examination of the neck if it is short, wide,
any deformity, or limitation in mobility (atlantooccipital extension) [32].
Some mnemonics are helpful for remembering patient factors that are associated with a difcult airway, such as MMMMASK (Table42.5):
and OBESE for difcult mask ventilation
(Table42.6) or LEMON (Table42.7).
Table 42.5 MMMMASK mnemonics difcult airway
MMMMASK Description
M Male gender
M Mask seal which is affected by bread or
M Mallampati grade 3 or 4
M Mandibular
A Age
S Snoring and OSA
K Kilograms (weight)
Table 42.6 OBESE mnemonics for difcult mask
ventilation
OBESE Description
O Obese (BMI >26kg/m
B Bearded
E Edentulous
S Snoring
E Elderly (>55years)
being edentulous
2
)
Table 42.7 LEMON mnemonics for airway assessment
LEMON Criterion Score
L Look externally:
– Facial trauma
– Large incisors
– Beard or mustache
– Large tongue
E Evaluate:
– Incisor distance
– Hyoid-mental distance
– thyroid-to-mouth distance
M Mallampati 1
O Obstruction 1
N Neck mobility 1
(1–4)
1
1
1
1
(1–3)
1
1
1
42.5.1.3 Specic Tests andScores
forAirway Assessment
Anatomical Criteria
Mouth Opening andInter-Incisor Gap (IIG)
The mouth opening is central to airway management and intubation. The reduced mouth
opening is associated with difcult laryngoscopy, intubation, and LMA insertion. The difculty lies in determining whether this is
mechanical or functional as the latter may
improve with general anesthesia and muscle
relaxation.
One helpful way to quantify mouth opening
is to ask the patient whether he/she can place
three fingers between their upper and lower
teeth. Whereas three fingerbreadths test is
ideal, anything less than two (around 3 cm)
predicts an increased risk of airway
difficulties.
An inter-incisor distance of less than 5cm or
two to three ngerbreadths may make conventional laryngoscopy difcult.
The mouth opening of 1.5cm or less than one
ngerbreadth may impair the insertion of a supraglottic airway device or laryngoscope and an
inter-incisor distance of 2cm is needed to insert
the intubating LMA (ILMA). At least 2.5cm is
required to insert an LMA.An IIG of 5 cm for
intubation and 4cm for the insertion of an LMA
is a simple test with a relatively high predictive
value [32, 33].
498
Pillars
a
GRADE I GRADE II GRADE IIIGRADE IV
IC
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N. A. Shallik et al.
Mallampati Score
Described in Mallampati’s original paper 1985,
this is assessed by asking the patient (in a sitting
or upright position) to open his/her mouth and
protrude the tongue maximally. Visibility of faucial pillars, soft palate, and uvula inside the
patient’s mouth will result in a score of one to
three. A Mallampati score of four was later
added.
Original Mallampati Scoring
• Class 1: Faucial pillars, soft palate, and uvula
could be visualized.
• Class 2: Faucial pillars and soft palate could
be visualized, but uvula was masked by the
base of the tongue.
• Class 3: Only soft palate visualized.
Modied Mallampati Scoring as in (Fig.42.3)
• Class I: Soft palate, uvula, fauces, pillars
visible.
• Class II: Soft palate, a major part of uvula,
fauces visible.
• Class III: Soft palate, a base of uvula visible.
• Class IV: Only hard palate visible.
Upper Lip Bite Test (ULBT)/Mandible
Protrusion Test
Described into three classes: (Fig.42.4)
• Class I: Lower incisors biting the upper lip,
making the mucosa of the upper lip totally
invisible.
• Class II: The same biting maneuver revealing
a partially visible mucosa.
• Class III: The lower incisors fail to bite the
upper lip.
• (ULBT Class II and III considered as difcult
intubation) [34].
Mandibular Space (Fig.42.5)
As mentioned above, we can do some measurements to assess the airway [32]:
1. Thyromental (TM) distance (Patil’s test): It is
dened as the distance from the mentum to the
thyroid notch while the patient’s neck is fully
extended. This measurement helps in determining how readily the laryngeal axis will fall
in line with the pharyngeal axis when the atlantooccipital joint is extended. Alignment of
Uvula
Hard palate
Soft palate
CLASS I
b
Fig. 42.3 Modied Mallampati Scoring (a) and Cormack and Lehane (CL) grades (b)
Vocal cords
CLASS II CLASS II
Epiglottis
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Hard palate
LASS IV
Class I Class II Class III
42 Dicult Airway Management forENT Surgery forNon-anesthesiologists
Fig. 42.4 Shows upper lip bite test (ULBT)/Mandible protrusion test
499
Fig. 42.5 Rule of 3-3-2
ngers
Rule 3-3-2
Fingers
Mouth opening= 3
Hyoid-mental= 3
Thyro- hyoid = 2
these two axes is difcult if the T-M distance is
<3 ngerbreadths or <6cm in adults; 6–6.5cm
is less difcult, while >6.5cm is normal.
2. Sterno-mental distance: It was measured with
the head fully extended on the neck with the
mouth closed. A value of less than 12 cm is
found to predict difcult intubation.
3. Mandibulo-hyoid distance: Measurement of
mandibular length from chin (mental) to hyoid
should be at least 4cm or three ngerbreadths.
It was found that laryngoscopy became more
difcult as the vertical distance between the
mandible and hyoid bone decreased.
L: Look externally for (facial trauma, large inci-
sors, beard or mustache, large tongue).
E: Evaluate the 3–3-2 rule (incisor distance< 3
ngerbreadths, distance < 3 ngerbreadths,
thyroid-to-mouth distance<2 ngerbreadths)
(Fig.42.5).
M: Mallampati (Mallampati score≥3).
O: Obstruction (presence of any condition like
epiglottitis, peritonsillar abscess, trauma).
N: Neck mobility (limited neck mobility).
Patients in the difcult intubation group have
higher LEMON scores.
The LEMON Score forAirway Assessment
Table42.7
This score has a maximum of 10 points calculated by assigning 1 point for each of the following LEMON criteria:
Direct Laryngoscopy View andFiber-Optic
Bronchoscopy
In 1984, Cormack and Lehane described classication according to the views obtained by direct
laryngoscopy based on the structures seen, as a
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N. A. Shallik et al.
way of simulating potential scenarios that trainee
anesthetists might face.
As you can see in the (Fig. 42.3), Cormack
and Lehane (CL) grades 1 (A), 2 (B), 3 (C), and
4 (D). (a) Laryngoscope blade; (b) epiglottis; (c)
glottic opening; (d) arytenoid cartilages.
According to the original denition by Cormack
and Lehane, most of the glottic opening can be
seen with grade 1. In grade 2, only the posterior
portion of the glottis or only arytenoid cartilages
are visible. In grade 3, only the epiglottis but no
portion of the glottis is visible, whereas, in grade
4, neither the glottis nor the epiglottis can be
seen [35].
Later on, a modied version that subdivided
Grade 2 was described in 1998, dividing it into
grade 2A and 2B, where is in 2A partial view
of the glottis, and 2B only arytenoids can be
seen [36].
42.5.1.4 Investigations
Routine imaging studies are not indicated for the
assessment of the airway, nonetheless, diagnostic
imaging studies provide valuable information
when dealing with head and neck pathologies.
Even though plain X-ray has low predictive
value for the prediction of a difcult airway, lateral exion-extension neck. X-ray might be of
help in patients with suspected atlantoaxial
instability.
More specic tests like magnetic resonance
images (MRI) and computed tomography (CT)
scan can be of value in particular situations.
Tumors with a mass effect that might compromise the airway passages invade the airway
lumen or displace the larynx would be detected
using MRI or CT scan.
Thyroid goiter or thyroid tumors with posterior extension can be evaluated with MRI scans.
They can also be helpful in detecting cases with
suspected tracheomalacia as well.
42.5.1.5 Nontraditional Airway
Assessment
Virtual Endoscopy (VE)
Over the past few years, astonishing progress has
been made in the eld of noninvasive imaging
and simulation. The introduction of multi-row
detector CT scanners has made it possible to
acquire high-resolution images of the airways
within a short time. Those images can then be
reconstructed into two-dimensional (2D) and
three-dimensional (3D) images, including internal virtual endoscopic (VE) renderings that
closely mimic images from conventional beroptic endoscopy. Using specialized VE software
that process surface and volume-rendering data,
the CT images can be reformatted into a 3D
model that would make performing a virtual
endoscopy possible.
Virtual endoscopy has many advantages over
conventional endoscopy. Since the images are of
equivalent quality to the live procedure, unnecessary patient’s discomfort is avoided, the use of
local anesthetics will not be needed avoiding the
hazards associated with their use, procedurerelated side effects like vomiting, coughing,
sneezing, potential aspirations or laryngeal
edema and spasm would be avoided as well.
Other potential hazards of conventional endoscopy that can be omitted as well include bleeding, pneumothorax, hypoxemia, and aspiration.
Moreover, the use of virtual endoscopy (VE)
can help in visualizing structures that cannot be
duplicated by any other means, an example, visualization of the posterior nares, the Eustachian
tube orices, and the subglottic regions. Also, it
can visualize areas that conventional endoscopy
cannot reach, providing physicians with data that
would ultimately alter airway management
decisions.
However, physicians must take into advisement that virtual endoscopy (VE) has some limitations; airway diameter readings might not be
accurate since it changes during the respiratory
cycle. Furthermore, visualizing supercial
lesions is less sensitive. Also, the presence of
retained mucus or blood can falsely be interpreted as tracheobronchial stenosis or a foreign
37].
body [
3D Reconstruction andDecision-Making
3D reconstruction of cross-sectional images provides physicians with images that are far easier to
comprehend, making the understanding of the
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42 Dicult Airway Management forENT Surgery forNon-anesthesiologists
501
extent of the pathological processes simpler that
would ultimately result in better clinical outcome
and better decision-making. Therefore, it is crucial that physicians from different specialties
familiarize themselves with the use of such
techniques.
Being familiar with the 3D reconstructed
image anatomy would help reading the images
faster and more precisely. This includes the evaluation of the airway proper using tissue transparent projection (TTP) and volume-rendering
techniques (VRT) protocols.
The Benets ofVE and3D Reconstructions
inAirway Management
VE and 3D reconstructions are one-stop shop in
the management of the difcult airway; After
performing the MDCT examination as well as the
post-processing methods, the following pearls
would be addressed and thoroughly commented
upon [38]:
1. Human airway canal (diameter, narrow seg-
ments including its sites, level, and quantitative assessment in mm regarding its caliber
and length for those following the application of modied Valsalva maneuver).
2. Posterior choana/nares (in children assess
choanal atresia) whether it is primarily bony
or membranous.
3. Nasal septum, deviation, swellings, Concha
Bullosa, or mucosal thickening, antrochoanal polyp, or inverted papilloma or other
nasal pathologies, antro-choanal polyp, or
inverted papilloma or other nasal
pathologies.
4. Dental assessment (panoramic-like view)
using curved multi-planar reconstruction to
show orthopantomogram (OPG) missed
teeth, loosening, or loss of the normal lamina
dura. Denture articial teeth or loose implant/
prosthesis also can be seen.
5. Dislocation of Temporomandibular Joint
(TMJ), dislocation, disorder, ankyloses,
osteoarthrosis, osteomyelitis, or fractures).
6. Assessment of cervical spine in case of
trauma to the cervical region.
7. Abnormal variants of blood vessels and
tumor blood supply in the head and neck
region.
8. Thyroid enlargement and retrosternal extension and its effect on the trachea, whether it
is displaced or compressed from outside or
invasion by the tumor.
9. Abnormal calcication of the styloid process
(Eagle syndrome).
10. The diameter of the tracheal and deviation
down to the carina and assessment for tracheomalacia or invasion of the tracheal tree
if any.
11. Laryngeal skeleton and abnormal position of
vocal cords.
12. Masses (soft tissue or hard tissues that may
be displacing/invading the airway).
13. Correlation with Mallampati score and suggestion of the oral versus nasal route for
intubation.
Below, you can nd an example of 3 cases that
clearly demonstrate the use of 3-D reconstruction and VE of upper airway and how these techniques solved the mystery of the diagnosis:
Case 1: Circular hyoid bone.
CT scan with 3D reconstruction demonstrated
a thick hyoid bone with abnormal circular conguration extending posteriorly forming an
incomplete ring that caused narrowing of the airway lumen at the supraglottic level. Moreover,
the thyroid cartilages’ superior Cornu also,
encroach on the airway column. Virtual reality of
the airway from frontal and lateral projections
showed stenosis of the airway at the supraglottic
region [39] (Fig.42.6).
Case 2: Preoperative clinical and nasendoscopic assessment in a patient with trauma to
upper airway revealed a web formation at the
level of the glottis extending from the anterior
commissure to the posterior one-third of the glottis. Virtual endoscopic (VE) evaluation showed
the web to be at a supraglottic region, while the
glottic region was clear. The nding changed the
airway management decision from performing an
advanced airway technique toward simple topicalization of the airway [40] (Fig.42.7).
502
ab
cd
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N. A. Shallik et al.
Fig. 42.6 Shows Volume Rendering Technique (VRT)
3-D reconstruction images from different perspectives for
the laryngeal cartilaginous framework: (a) Craniocaudal
projection, (b) Right lateral, (c) Posterior, (d) Anterior
projection Showing incomplete ring formation of the
Case 3: Presented with a hard tissue mass arising from the lateral aspect of airway.
Nasendoscopic examination showed a normal
vocal cord movement. The nature of the mass
hyoid bone forming incomplete ring/circle with overriding of the posterior ends. Similar ndings are also noted
within the superior Cornu of the thyroid cartilages. (Image
courtesy Dr. Nabil Shallik and Dr. Abbas Moustafa).
couldn’t be revealed with either endoscopy or CT
scan. The CT 3D reconstruction revealed abnormally congured hyoid bone, leading to mild
oropharyngeal airway narrowing. The scan
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ab
42 Dicult Airway Management forENT Surgery forNon-anesthesiologists
Fig. 42.7 Flexible brotic view showing the stenotic glottic opening (Image courtesy Dr. Nabil Shallik)
503
revealed that the mass is part the hyoid bone,
pushed away to one side by the thyroid mass
leading to bizarre looking airway. With the use of
VE, the diameter of the airway was determined.
Surgical, as well as anesthesia plans, were formulated accordingly [41] (Fig.42.8).
Preoperative Endoscopic Airway
Examination (PEAE)
The routine bedside examination of the airway is
poorly predictive for difcult tracheal intubation,
in part due to the limitation in detecting the presence of pathologies of the upper airway during
the inspection. The preoperative use of beroptic endoscopic airway examination (PAEA) by
ENT surgeons or trained anesthetists in Difcult
Airway Clinic (DAC) provides valuable information when assessing patients with supraglottic,
the base of the, or vocal cord masses. As well as
helps with evaluating the dynamic movement of
the vocal cords; hence the examination is usually
done as a bedside test under local anesthesia. It is
the most reliable method that assess the entirety
of the upper airway under dynamic conditions
before induction of general anesthesia and is one
of the recommendations of NAP4 (Fig.42.9).
1. Nasopharyngeal endoscopic airway assessment
helps the anesthesiologists with formulating a
plan to manage patients with a potential difcult airway. A prospective study that investi-
gated whether preoperative endoscopic airway
examination (PEAE) would affect airway
management decision-making found that the
use of PEAE would reduce the use of unnecessary awake intubation by 26% [42].
2. Tracheoscopy also be done also after spraying
the vocal cord and tracheal of the patient with
local anesthesia by unique technique and need
an expert operator to do it without complication. (Fig.42.10).
42.6 Future Plane inAirway
Management
42.6.1 Airway Ventilation Through
“Straw”
42.6.1.1 Evone andTritube
inStenotic Airway
Flow control ventilation (FCV) is a recently
developed ventilation strategy which allows
keeping the intrapulmonary pressures low while
achieving optimal gas exchange [43]. It has
been proven in animal models to improve pulmonary function and oxygenation [44] and in
cases with acute respiratory distress syndrome
(ARDS) [45].
Ventilation through a small endotracheal tube
is not uncommon in airway management. It can
be used in elective upper airway surgery as well
504
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N. A. Shallik et al.
b
d
Fig. 42.8 Shows (a) 3-D reconstruction images for the
laryngeal skeleton and bony framework, (b) shaded surface display (SSD) 3-D reconstruction of the airway.
Showing axial rotation and right lateral displacement of
the hyoid bone as well as the infrahyoid, laryngeal and
proximal tracheal airway which is indented and
as emergency ventilation through needle cricothyrotomy. The traditional use of jet ventilation
by small endotracheal tubes is challenging
because of the increased risk of barotrauma and
inadequate gas exchange [43]. Keeping in mind
that expiration during jet ventilation is a passive
process.
Flow Controlled Ventilation (FCV) mode is a
unique ventilation technique in which inspiration as well as expiration are controlled pro-
encroached upon with signicant reduction of its lumen
caliber and appreciable narrowing. but (c) and (d) show
the endoscopic view of nasendoscopic examination of
upper airway (Image courtesy Dr. Nabil Shallik and
Dr. Abbas Moustafa)
cesses. This is achieved by generating a
continuous ow into the patient’s lungs during
inspiration and a constant (negative) ow, sucking gasses out of the patient’s lungs during expiration. The FCV mode does not allow for
ventilation pauses, and this results in linear
increases and decreases in intratracheal pressures (Fig.42.11b). Therefore, the mean airway
pressure will be higher compared to conventional large bore Volume Controlled Ventilation
AL GRAWANY
42 Dicult Airway Management forENT Surgery forNon-anesthesiologists
Fig. 42.9 Preoperative Endoscopic Airway Examination (PEAE) of the upper airway. (Image courtesy Dr. Nabil
Shallik)
505
a c
b d
Fig. 42.10 Tracheoesophageal stula (a) and (b) red arrow shows carina and blue arrow shows esophagus and (c). (d)
Tracheal stenosis nicely demonstrated by tracheoscopy under local anesthesia. (Image courtesy Dr. Nabil Shallik)
506
intratracheal pressure
de
N. A. Shallik et al.
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a
c
b
peak pressure
EEP
time
Fig. 42.11 (a) Evone ventilator, (b) intratracheal pressure waves, (c) small diameter tritube and (d), (e) ventrain during
inspiration and expiration
(VCV) or Pressure Controlled Ventilation
(PCV). The bronchiole and alveoli will be more
opened (stretched) during ventilation facilitating oxygen uptake in the blood. Moreover, the
continuous gas ow enhances the gas mixture in
the lungs while also improving the gas exchange.
FCV results in higher efcient ventilation compared to conventional ventilation techniques.
Evone is the only commercially available ventilator applying FCV ventilation mode
(Fig. 42.11a), which is based on a controlled
inspiration and expiration ow from a set PEEP
Tritube has three lumens: a ventilation lumen
with Murphy’s eye; a cuff lumen to inate and
deate the high-volume and low-pressure cuff;
and an intratracheal pressure measurement lumen
for continuous intratracheal pressure measurements. Additionally, it has a malleable stylet to
facilitate intubation [46, 47].
With this small diameter tube, it carries a risk
of aspiration, however, the presence of inatable
cuff decreases this risk without increasing chance
for air trapping-induced barotrauma, as in traditional jet ventilation [48–50].
to set peak pressure and vice versa. The inspiratory ow is continuously controlled by advanced
mass ow regulators and the expiratory ow is
controlled by regulated suctioning.
Evone or Ventrain (Ventinova Medical B.V.,
Eindhoven, The Netherlands) is used in combination with Tritube which has a small caliber (less
than 3mm inner diameter ID and 4.4mm outer
diameter OD) (Fig. 42.11c), enabling highly
accurate intratracheal pressure measurements
and securing the airway with an inatable cuff as
FCV ventilation requires a sealed airway.
With this small outer diameter (OD), it gives
more space in the oral cavity, improves the surgical eld, and decreases post-extubation throat
pain due to tracheal tube size.
42.6.1.2 Ventrain
Ventrain (Ventinova Medical B.V., Eindhoven,
The Netherlands) (Fig.42.11d, e) is a manually
operated small lumen ventilator (manual Evone)
that was initially used to ventilate patients with
obstructed upper airway following a needle cricothyrotomy [51]. Oxygen is supplied during
inspiration and expiration is initiated by actively
removing gas from the lungs through jet-ow
generated suction based on Bernoulli’s principle.
This technology has been introduced as expiratory
ventilation assistance (EVA) [52]. Compared to
the traditional jet ventilation, active removal of
gas from the lungs will reduce the risk of intrapulmonary pressure build-up by air trapping,
AL GRAWANY
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