1. Introduction
When temporary mechanical ventilation is required, either in the
treatment of respiratory failure, or during surgery with muscular
relaxation, endotracheal intubation is usually the preferred method
of airway management.
Why is this the preferred means of airway management?
The primary reason is that it provides a "protected" airway.
Protected from what you ask?
Well, protected from introduction of foreign matter, particularly
gastric contents.
The accurate placement of an endotracheal tube requires skill.
Usually the patient is rendered unconscious and immobile (including
paralysis of the muscles of respiration) for the placement. Obviously
inability to rapidly obtain control of the patient's airway in this
setting would be "bad" if not lethal.
The airway examination is an effort to identify those patients in
whom conventional endotracheal intubation will be difficult. It is
vitally important to recognize such patients BEFORE administering
medications that induce apnea.( Lack of breathing)
Endotracheal Intubation
mohammad reza rajabi
Page 1 4/3/2012

2. Endotracheal Tube
Acknowledgements
This educational site was developed by
Tammy Euliano, MD, Associate Professor of Anesthesiology
with the assistance of
future doctor Amy Lee
programmers Karthik Paladugu and Rick Lockwood
graphic artist future doctor Christopher Hurt.
Major contributions were provided by
Ilona Schmalfuss, MD, Assistant Professor of Radiology
Jeremy Melker, MD, Otolaryngology Resident.
Funding was provided by the
University of Florida College of Medicine Education Committee.
mohammad reza rajabi
Page 2 4/3/2012

3. Aspiration of Gastric Contents
The risk of passive reflux of gastric contents into the pharynx is
increased when the stomach is full. If the gag reflex has been
blunted (by alcohol ingestion, decreased mental status or
medications), the acidic volume can make its way into the trachea
causing potentially extensive damage.
Aspiration Prevention
In this case, which of the following could reduce the risk of
aspiration and its consequences?
Wait 6 hours before proceeding keeping the patient NPO
Yes No
(yes) Incorrect! - Nil per os
While this will help for elective surgery patients, trauma patients and
those with acute GI problems will not empty their stomachs well. In
addition this operation should not be postponed for any length of
time due to the risk of appendix rupture and/or sepsis.
(no)Correct!
While a 6-hour NPO period is ideal, this surgery should not be
postponed.
Administration of a "non-particulate" antacid
Yes No
(yes)Correct ! - Non-particulate antacid
Many would advocate having the patient drink 15-30cc sodium
citrate or bicitra within 30 minutes of induction of anesthesia.
Though this increases the stomach volume, it is actually protective
mohammad reza rajabi
Page 3 4/3/2012

4. as it raises the pH of the stomach contents, reducing injury to the
lung in the event of an aspiration.
(no)Incorrect ! - Non-particulate antacid
Many would advocate having the patient drink 15-30cc sodium
citrate or bicitra within 30 minutes of induction of anesthesia.
Though this increases the stomach volume, it is actually protective
as it raises the pH of the stomach contents, reducing injury to the
lung in the event of an aspiration
Administration of H2 blockers
Yes No
(yes)Correct ! - H2 Blockers
The onset time of these medications is 30+ minutes, and even then
they do not affect the pH of the volume already in the stomach.
However, new fluid will be secreted into the stomach at a higher pH,
perhaps increasing the overall pH by the time of emergence from
anesthesia (the other time at which patients are at risk for
aspiration).
(no)Incorrect ! - H2 Blockers
The onset time of these medications is 30+ minutes, and even then
they do not affect the pH of the volume already in the stomach.
However, new fluid will be secreted into the stomach at a higher pH,
perhaps increasing the overall pH by the time of emergence from
anesthesia (the other time at which patients are at risk for
aspiration).
Administration of metoclopramide
Yes No
mohammad reza rajabi
Page 4 4/3/2012

5. (yes)Correct! - Metoclopramide
Metoclopramide speeds gastric emptying and increases the lower
esophageal sphincter (LES) pressure. While the latter is helpful at
reducing the risk of aspiration within minutes, stomach volume
reduction takes more time. This emptying should occur, however,
and can reduce the risk of aspiration during emergence and
extubation at the end of the operation. There are some risks to
metoclopramide so, as with everything, a risk:benefit evaluation
must be performed.
(no)Incorrect! - Metoclopramide
Metoclopramide speeds gastric emptying and increases the lower
esophageal sphincter (LES) pressure. While the latter is helpful at
reducing the risk of aspiration within minutes, stomach volume
reduction takes more time. This emptying should occur, however,
and can reduce the risk of aspiration during emergence and
extubation at the end of the operation. There are some risks to
metoclopramide so, as with everything, a risk:benefit evaluation
must be performed.
Rapid Sequence Induction
Yes No
(yes)Correct! - Rapid Sequence Induction
Following pre-oxygenation, the patient is put to sleep with a rapid
acting IV induction agent such as sodium thiopental, immediately
followed by succinylcholine (or other rapid-acting agent), application
of cricoid pressure , and intubation of the trachea.
Positive pressure mask ventilation is not performed to avoid
increasing gastric volume. The purpose of this technique is to
minimize the duration of impaired gag reflex prior to intubation
Cricoid Pressure during intubation
Yes No
mohammad reza rajabi
Page 5 4/3/2012

6. (no) Incorrect! - Cricoid Pressure during Intubation
An assistant identifies the cricoid ring and applies pressure,
compressing the esophagus against the underlying vertebral
body. This prevents passive reflux of gastric contents into the
lung. How much pressure to apply is a continuing question,
current recommendations suggest approximately 10 Newtons
(1 kg) of force (mild discomfort for the patient), as the induction
medications are being administered. Once the patient loses
consciousness, the cricoid pressure should be increased to
approximately 30 Newtons (3 kg). It is possible for this pressure
to make intubation more difficult and some reduction in force
may be necessary.
(yes)Correct! - Cricoid Pressure during Intubation
An assistant identifies the cricoid ring and applies pressure,
compressing the esophagus against the underlying vertebral
body. This prevents passive reflux of gastric contents into the
lung. How much pressure to apply is a continuing question,
current recommendations suggest approximately 10 Newtons
(1 kg) of force (mild discomfort for the patient), as the induction
medications are being administered. Once the patient loses
consciousness, the cricoid pressure should be increased to
approximately 30 Newtons (3 kg). It is possible for this pressure
to make intubation more difficult and some reduction in force
Endotracheal Intubation
Intubation is typically performed under direct visualization. That is,
by looking through the mouth directly at the vocal cords (direct
laryngoscopy), and watching the endotracheal tube pass through the
cords and into the trachea. However, there is no direct line-of-sight
from the mouth to the vocal cords.
Check in a mirror or examine a friend (preferably one who has not
eaten onions recently), even with the mouth maximally opened and
tongue extended you cannot see the vocal cords, in fact only rarely
can you see the epiglottis.
mohammad reza rajabi
Page 6 4/3/2012

7. Mallampati Classification
Actually, the amount of the posterior pharynx you can visualize is
important and correlates with the difficulty of intubation.
Visualization of the pharynx is obscured by a large tongue (relative
to the size of the mouth), which also interferes with visualization of
the larynx on laryngoscopy. The Mallampati Classification is based on
the structures visualized with maximal mouth opening and tongue
protrusion in the sitting position (originally described without
phonation, but others have suggested minimum Mallampati
Classification with or without phonation best correlates with
intubation difficulty).
mohammad reza rajabi
Page 7 4/3/2012

8. Class I: soft palate, fauces, uvula, pillars
Class II: soft palate, fauces, portion of uvula
Class III: soft palate, base of uvula
Class IV: hard palate only
Other Predictors of Difficult Intubation
 Obesity – body weight > 110kg
 Mouth opening – inter-incisor distance < 4cm in an adult
 Ability to prognath – a large overbite, or the inability to shift
the lower incisors in front of the upper incisors
 Thyromental distance – The distance from the thyroid cartilage
to the mentum (tip of the chin) should be > 6.5-7 cm.
 Mentum-Hyoid distance – Similar to thyromental distance, and
should be at least 3-4 finger-breadths.
Many other factors have been investigated with variable results.
Other factors that may indicate a difficult intubation
 Sternomental distance – Similar to above, measured from the sternum
to the tip of the mandible with the head extended. This measure is
influenced by neck extension. Should be >12.5cm.
 Mandibulohyoid distance – the vertical distance between the mandible
and the hyoid bone, determined radiographically. This may be
increased with a short mandibular ramus or a caudally located hyoid
bone. Such an increase in this distance may be associated with difficult
intubation {Chou 1993}
 Thyrosternal distance – <8cm may suggest difficulty, probably related to
the caudally located hyoid as above.
mohammad reza rajabi
Page 8 4/3/2012

9.  Various radiographic measurements of the cervical spine, its alignment
with airway structures and the atlanto-occipital joint.
Positioning
To obtain a direct line of sight, the patient is positioned in the
"sniffing position." The neck is flexed at the lower cervical spine and
extended at the atlanto-occipital joint. This flexion and extension is
amplified during laryngoscopy.
The patient’s neck mobility should be assessed preoperatively by
having them flex and extend their head maximally. The range of
motion should be more than 90°. Motion less than 80° may triple the
risk of a poor view at laryngoscopy.
mohammad reza rajabi
Page 9 4/3/2012

10. Direct Laryngoscopy
Then a laryngoscope is used to pull the lower jaw and tongue up and
out of the way.
The metal blade is passed into the mouth to the level of the
epiglottis, then with an anterior and caudad motion (ie toward the
edge of the ceiling across the room) , the lower jaw is elevated,
allowing visualization of the glottic structures.( The glottis is the
structures of phonation including the vocal cords and surrounding
structures.) In most patients this results in a clear view of the larynx
and the endotracheal tube is passed through the vocal cords under
direct visualization.
mohammad reza rajabi
Page 10 4/3/2012

11. Laryngoscopy Grades
In most patients Direct Laryngoscopy results in a clear view of the
larynx. The laryngeal view has been classified by Cormack and
Lehane as follows:
Grade 1: Full view of the glottis
Grade 2: Only the posterior commissure is visible
Grade 3: Only the epiglottis is seen
Grade 4: No epiglottis or glottis structure visible
Airway Review
What might make Direct Laryngoscopy and Intubation more difficult?
Inability to open the mouth
Yes No
(yes)Correct!
There must be room to place the laryngoscope in the mouth…usually
at least 3 finger breadths in the adult.
(no)Incorrect!
There must be room to place the laryngoscope in the mouth…usually
at least 3 finger breadths in the adult.
mohammad reza rajabi
Page 11 4/3/2012

12. Inability to extend the neck
Yes No
(yes)Correct!
The "sniffing position" requires significant neck extension.
(no)Incorrect!
The "sniffing position" requires significant neck extension.
Inability to breathe through the nose
Yes No
(no)Correct!
Unless a nasal intubation is planned.
(yes)Incorrect!
Unless a nasal intubation is planned.
Large tongue
Yes No
(yes)Correct!
Also if it is immobile, as from radiation therapy.
(no)Incorrect!
Also if it is immobile, as from radiation therapy.
Redundant pharyngeal tissue
Yes No
(yes)Correct!!
This occurs with obesity, and is often suggested by a history of
snoring and/or obstructive sleep apnea.
mohammad reza rajabi
Page 12 4/3/2012

13. (no)Incorrect!
This occurs with obesity, and is often suggested by a history of
snoring and/or obstructive sleep apnea.
Case 2 : Abnormal Exam
A healthy 25-year-old man is scheduled to have a shoulder repair
requiring general anesthesia.
Let's review his airway examination.
What would you like the patient to do:
Open his mouth as wide as possible
Extend his neck as far as possible without pain
View from the side
mohammad reza rajabi
Page 13 4/3/2012

14. Open Mouth
This patient's mouth opening is 2 finger-breadths, the soft palate is
barely visible on maximal mouth opening.
Neck
mohammad reza rajabi
Page 14 4/3/2012

15. View from the side
2 finger-breadths fit between the tip of the chin and the neck.
Airway Examination
Mouth opening
Normal
Reduced
What is mouth opening?
(normal)Incorrect
it is less than 3 finger breadths.
mohammad reza rajabi
Page 15 4/3/2012

16. (reduced)Correct
The mouth opening is less than 3 finger-breadths.
Open Mouth
The inter-incisor distance on maximal mouth opening. Should be >4
cm in an adult, or 3-4 of the patient's finger-breadths.
This patient's mouth opening is 2 finger breadths, the soft palate is
barely visible on maximal mouth opening.
Mallampati Score
I
II
III
IV
What is Mallampati Score?
mohammad reza rajabi
Page 16 4/3/2012

17. (I)Incorrect
The uvula cannot be seen.
(II)Incorrect
Not even the top of the uvula is visible.
(III)Yes
All structures visible up to the soft palate is a Mallampati Class III.
(IV)Incorrect
The soft palate is visible.
Mentum-Hyoid distance
Normal
Reduced
What distance?
(normal)Incorrect
3 finger-breadths is normal, this patient has only 2.
(reduced)Yes
this is less than the normal 3 finger-breadths.
View from the side
2 finger-breadths fit between the tip of the chin and the neck.
mohammad reza rajabi
Page 17 4/3/2012

18. Neck Extension
Normal
Reduced
What is neck extension?
(normal)Correct
The neck extends.
(reduced)Incorrect
The neck motion is > 90 degrees.
Neck
The range of motion should be more than 90°. Motion less than 80° may triple the risk
of a poor view at laryngoscopy.
Airway Evaluation Summary
Because of the reduced mentum-hyoid distance, it may be difficult to
visualize the larynx with traditional direct laryngoscopy. There are
other options, including other blades and techniques that do not
require a direct line-of-sight, which are beyond the scope of this site.
Perhaps the most conservative method of securing the airway of a
patient who is anticipated to have a "difficult airway" is with awake
fiberoptic intubation. This technique requires substantial skill, but
allows intubation in an awake, spontaneously breathing patient. The
trachea is identified with a flexible fiberscope, and then the
endotracheal tube is advanced over the fiberscope like a stylet. Such
mohammad reza rajabi
Page 18 4/3/2012

19. a procedure requires blockade of the sensory innervation to the
airway, and blunting of the gag reflex.
Innervation of the Upper
Airway
Awake fiberoptic intubation requires topical anesthesia for patient
comfort, as well as to blunt the gag reflex that would prevent
successful intubation of the trachea.
Several nerves are involved in the sensation of the upper airway:
 Anterior 2/3 of the tongue - Trigeminal nerve (V).
 Posterior 1/3 of tongue to epiglottis - Glossopharyngeal nerve
(IX; afferent limb of gag reflex).
 Epiglottis to vocal cords - Internal branch of Superior Laryngeal
Nerve (Vagus, X)
mohammad reza rajabi
Page 19 4/3/2012

20.  Trachea below vocal cords - Recurrent Laryngeal Nerve
(Vagus, X)
MOTOR INNERVATION
Motor innervation to the larynx is provided by the Vagus Nerve, but
recall there are two branches involved. The Recurrent Laryngeal
Nerve innervates all the muscles of the larynx EXCEPT the
cricothyroid muscle, which is innervated by the External Branch of
the Superior Laryngeal Nerve. Because the function of the
cricothyroid muscle is to stretch and tense the vocal cords,
unopposed action of the cricothyroid, as may occur with bilateral
destruction of the recurrent laryngeal nerves, would lead to stridor,
respiratory distress and possibly airway obstruction.
GAG REFLEX
So the sensory, afferent limb of the gag reflex is the
glossopharyngeal nerve (IX), while the motor, efferent limb is the
Vagus (X).
It's not much of a mnemonic, but I remember this as a variant of
TGIF: "Thank God it's Recurrent" I know, it's lame, perhaps just
lame enough to be memorable!
Airway Blocks
Topical application of local anesthetics is usually sufficient for the
tongue and oro/nasopharynx, though glossopharyngeal blocks are
performed occasionally. Blunting of the gag reflex requires
Transtracheal (really translaryngeal) with or without bilateral
Superior Laryngeal Nerve blocks as shown below.
mohammad reza rajabi
Page 20 4/3/2012

21. The superior laryngeal nerves are blocked by deposition of 1%
lidocaine near where the nerves penetrate the thyrohyoid
membrane. The transtracheal block is accomplished with 4%
lidocaine injected directly into the tracheal lumen. Often this block
alone, coupled with nebulized or atomized lidocaine is sufficient for
awake intubation.
mohammad reza rajabi
Page 21 4/3/2012

22. Airway Structures
The right panel displays images seen during fiberoptic bronchoscopy.
The corresponding level on CT is displayed on the middle panel.
Place the cursor over structures to learn their identity.
mohammad reza rajabi
Page 22 4/3/2012

23. mohammad reza rajabi
Page 23 4/3/2012

24. Review of Airway Innervation
Let's review the innervation of the upper airway:
mohammad reza rajabi
Page 24 4/3/2012

25. Purple
Facial (VII) Trigeminal (V)
Glossopharyngeal (IX) Vagus (X)
(VII)No
The Facial Nerve supplies only taste to the tongue.
(V)Yes
The maxillary branch (V2) supplies the nasal cavity and palate, while
the mandibular branch (V3) supplies the anterior 2/3 of the tongue.
(IX)Incorrect
The glossopharyngeal nerve supplies sensation to the posterior 1/3
of the tongue and its overlying structures including the soft palate.
(X)No
The vagus innervates the airway further distal.
Green
Facial (VII) Trigeminal (V)
Glossopharyngeal (IX) Vagus (X)
(VII)No
The Facial Nerve supplies only taste to the tongue.
(IX)Yes
The glossopharyngeal nerve supplies sensation to the posterior 1/3
of the tongue and it's overlying structures including the soft palate.
(V)No
The maxillary branch (V2) supplies the nasal cavity and palate, while
the mandibular branch (V3) supplies the anterior 2/3 of the tongue.
(X)No
The vagus innervates the airway further distal.
mohammad reza rajabi
Page 25 4/3/2012

26. Blue
Facial (VII) Trigeminal (V)
Glossopharyngeal (IX) Vagus (X)
(VII)No
The Facial Nerve supplies only taste to the tongue.
(IX)No
The glossopharyngeal nerve supplies sensation to the posterior 1/3
of the tongue and it's overlying structures including the soft palate.
(V)No
The maxillary branch (V2) supplies the nasal cavity and palate, while
the mandibular branch (V3) supplies the anterior 2/3 of the tongue.
(x)Yes, but which branch
Internal branch of superior laryngeal
External branch of superior laryngeal
Recurrent laryngeal
(Yes
The Internal Branch of the Superior Laryngeal Nerve provides
sensory innervation to the mucous membrane from the epiglottis to
and including the vocal cords.
Incorrect
The External Branch of the Superior Laryngeal nerve provides motor
innervation to the cricothyroid muscle only.
Incorrect
The Recurrent Laryngeal Nerve supplies sensory innervation to the
trachea below the vocal cords, as well as motor innervation to all the
intrinsic muscles of the larynx except the cricothyroid muscle.. )
mohammad reza rajabi
Page 26 4/3/2012

27. Red
Facial (VII) Trigeminal (V)
Glossopharyngeal (IX) Vagus (X)
(VII)No
The Facial Nerve supplies only taste to the tongue.
(IX)No
The glossopharyngeal nerve supplies sensation to the posterior 1/3
of the tongue and it's overlying structures including the soft palate.
(V)No
The maxillary branch (V2) supplies the nasal cavity and palate, while
the mandibular branch (V3) supplies the anterior 2/3 of the tongue.
(x)Yes, but which branch
Internal branch of superior laryngeal
External branch of superior laryngeal
Recurrent laryngeal
(Incorrect
The Internal Branch of the Superior Laryngeal Nerve provides
sensory innervation to the mucous membrane from the epiglottis to
and including the vocal cords.
Incorrect
The External Branch of the Superior Laryngeal nerve provides motor
innervation to the cricothyroid muscle only.
Yes
The Recurrent Laryngeal Nerve supplies sensory innervation to the
trachea below the vocal cords, as well as motor innervation to all the
intrinsic muscles of the larynx except the cricothyroid muscle..)
mohammad reza rajabi
Page 27 4/3/2012

28. Case 3: Spine Evaluation
A previously healthy 40-year-old male presents with an open femur
fracture from a Motor Vehicle Accident (MVA) that needs to be
repaired under general anesthesia. He is currently on a backboard
with a cervical collar in place and is hemodynamically stable.
Examination of this patient's airway is complicated by the presence
of the cervical collar, which both inhibits mouth opening and by
definition prevents neck extension. As you have seen above, neck
extension is required for direct laryngoscopy.
So what shall we do?
Remove the neck collar and intubate as usual.
Intubate with a technique that does not require neck movement.
Avoid general anesthesia and perform a regional block for the
procedure.
Perform studies to "clear" the cervical spine.
First a basic review of the anatomy is helpful.
Recall that the cervical spine consists of 7 vertebrae, the first two of
which are highly specialized.
(Should this patient have an unstable cervical spine, the movement
resulting from laryngoscopy could permanently damage the spinal
cord, likely resulting in quadriplegia.)
(There are numerous techniques (retrograde intubation,…) purported
to involve less cervical spine motion, each of which requires
substantial skill and experience. These should only be attempted by
experienced practitioners. Some advocate "in-line stabilization"
where a second person attempts to hold the cervical spine still while
the primary person attempts direct laryngoscopy. This technique
makes intubation more difficult, and is inadequate for stabilization.)
mohammad reza rajabi
Page 28 4/3/2012

29. (While an attractive option, many would argue that anytime a
regional anesthetic is planned, immediate endotracheal intubation
must be possible. Complications may occur during the regional block,
or it may be inadequate for the operation, or wear off before the
surgeons are done. Therefore, inability to emergently intubate a
patient is a relative contraindication to regional anesthesia and
should be considered in this patient with a possible unstable neck.)
(Great idea!)
Cervical Spine Anatomy-Atlas
C1: The Atlas is a ring that interacts with the skull base above and
C2 shown on next page. It is unique in that it lacks a vertebral body
and spinous process. The articulation of C1 with the occiput is very
tight, providing little of the flexion of the cervical spine and only
about 20 degrees of extension.
mohammad reza rajabi
Page 29 4/3/2012

30. Cervical Spine Anatomy-Axis
C2: The Axis has an unusual thumb-like extension of its vertebral
body that passes through the arch of C1. This process is called the
dens or odontoid. The odontoid process is normally held very tightly
against the anterior arch of C1 by the transverse ligament.
Meanwhile the spinal cord travels behind the odontoid within the
arch of C1.
mohammad reza rajabi
Page 30 4/3/2012

31. Atlanto Axial Joint
This atlanto-axial joint provides the majority of the rotational motion
of the cervical spine. Meanwhile flexion and extension are primarily
accomplished at C2 and below, and particularly between C4 and C6.
Neck Movement with DL
What happens to the neck during direct laryngoscopy and
intubation?
As you have seen, the sniffing position involves neck flexion in the
lower cervical spine with extension superiorly. In the process of
direct laryngoscopy this motion is accentuated. As the laryngoscope
is lifted upward, the occiput is extended primarily at the atlanto-
occipital joint (occiput-C1), while flexion occurs at C2-3 and below.
Therefore, any intervention that impedes this flexion and extension
will make visualization of the glottis more difficult. In someone with
a cervical fusion up to the occiput it is pretty much impossible to
perform direct laryngoscopy. Similarly, a patient with external
stabilization such as a c-collar in this case will (SHOULD) have neck
movement reduced sufficient to make visualization difficult if not
impossible.
mohammad reza rajabi
Page 31 4/3/2012

32. Clearing the C-Spine
How does one rule out damage to the cervical spine?
At present history is our greatest ally. If the healthy patient has no
history of neck problems and no symptoms on maximal flexion and
extension, they are unlikely to have cervical spine disease.
On the other hand there are many patients whose cervical spine
SHOULD be radiographically evaluated pre-operatively including
certain trauma patients, as well as those with disease states that
affect the cervical spine including rheumatoid arthritis and Down's
Syndrome. These diseases may affect the transverse ligament and
thus the stability at the atlanto-axial joint.
Nexus Criteria
Which trauma patients require cervical spine films prior to surgery or
intubation?
There is a set of criteria identified by the National Emergency X-
Radiography Utilization Study (NEXUS) that attempt to identify
patients with a low probability of injury, thereby reducing the
number of negative cervical spine radiographs taken.
The criteria include
 No midline cervical tenderness
 No focal neurologic deficit
 Normal alertness
 No intoxication
 No painful, distracting injury that might make them ignore their
neck pain
For those patients whose cervical spine is not cleared, the
anesthesiologist must consider the risks of cervical spine damage
that can be worsened through direct laryngoscopy, versus the risk of
alternative techniques that may minimize neck motion, including
awake fiberoptic intubation. A description of these alternate
techniques is beyond the scope of this site at present.
mohammad reza rajabi
Page 32 4/3/2012

33. Spine Film
For the current case the following film is obtained.
Patient's Film Normal for Comparison
mohammad reza rajabi
Page 33 4/3/2012

34. Explanation
Note the large step-off between C6 and C7. This subluxation causes
entrapment of the spinal cord and damage.
Therefore this patient requires an intubation technique with minimal
neck motion and awake positioning,as well as some external
stabilization or operative intervention to prevent damage to the
spinal cord at the neck.
mohammad reza rajabi
Page 34 4/3/2012

35. C-Spine Review
So which patients are at higher risk for neck injury during
intubation?
Trauma patients
Yes No
(yes)Correct!
They may have trauma to the cervical spine as well.
(no)Incorrect!
They may have trauma to the cervical spine as well.
Rheumatoid arthritis patients
Yes No
(yes)Correct!
Approximately 30% of patients with severe disease will have some
instability at C1-C2. All should have periodic flexion or extension
xrays, particularly prior to surgery.
(no)Incorrect!
Approximately 30% of patients with severe disease will have some
instability at C1-C2. All should have periodic flexion or extension
xrays, particularly prior to surgery.
Down's Syndrome patients
Yes No
(yes)Correct!
About 15% of these patients have laxity in the transverse ligament
that holds the odontoid against the anterior arch of C1. Xrays are
also recommended in these patients prior to anticipated neck
manipulation including laryngoscopy.
mohammad reza rajabi
Page 35 4/3/2012

36. (no)Incorrect!
About 15% of these patients have laxity in the transverse ligament
that holds the odontoid against the anterior arch of C1. Xrays are
also recommended in these patients prior to anticipated neck
manipulation including laryngoscopy.
Osteoarthritic patients
Yes No
(yes)Incorrect
They are not at higher risk.
(no)Correct
They are not at higher risk
Patient with a prior cervical spine fusion
Yes No
(yes)Incorrect
Assuming the repair is stable and there is no further disease there is
little risk of damage. Such patients may be difficult to intubate,
though, if their mobility is significantly limited.
(no)Correct
Assuming the repair is stable and there is no further disease there is
little risk of damage. Such patients may be difficult to intubate,
though, if their mobility is significantly limited.
mohammad reza rajabi
Page 36 4/3/2012

37. Airway References
Cricoid Pressure
Vanner RG, Asai T. Safe use of cricoid pressure. Anaesthesia 1999: 54: 1-3. A review
of literature with recommendations.
Sellick BA. Cricoid pressure to control regurgitation of stomach contents during
induction of anaesthesia. Lancet 1961; 2: 404-6. The original description.
Views and Grades
Mallampati SR, Gatt SP, et al. A clinical sign to predict difficult tracheal intubation: a
prospective study. Can Anaesth Soc J 1985;32(4):429-434. The original
paper describing the classification system, but only 3 grades (III and IV
combined).
Samsoon GLT and Young JRB. Difficult tracheal intubation: a retrospective study.
Anaesthesia 1987;42:487-490. Describes the addition of Mallampati class 4
Cormack RS and Lehane J. Difficult tracheal intubation in obstetrics. Anaesthesia
1984;39:1105-1111. Describes the laryngoscopy grades and correlates with
difficult intubation. Also proposes a technique of attempting to intubate while
intentionally achieving a suboptimal (Class III) view.
Studies of Predictive Indices
There are many studies, some which counter others. One difficulty is defining
a difficult airway. Most use a Cormack-Lehane laryngoscopy grade of III-IV.
Some investigate specific radiographic measurements that are impractical in
daily clinical practice. Below are a few useful references:
El-Ganzouri AR, McCarthy RJ, et al. Preoperative airway assessment: Predictive
value of a multivariate risk index. Anesth Analg 1996;82:1197-1204. A logistic
regression comparing examination tests and developing a risk index.
Chou HC, Wu TL, et al. Mandibulohyoid distance in difficult laryngoscopy. Br J
Anaesth 1993; 71:335-339. A single article sighting this distance as an
important factor in an analysis of only 11 patients.
Frerk CM. Predicting difficult intubation. Anaesthesia 1991;46:1005-1008. A study
suggesting that a Mallampati Class III or IV with thyromental distance of <7cm
is sensitive and specific for difficult intubation (laryngoscopy grade 3 or 4).
C-Spine Evaluation
mohammad reza rajabi
Page 37 4/3/2012

38. Hoffman JR, Mower WR, et al. Validity of a set of clinical criteria to rule out injury to
the cervical spine in patients with blunt trauma. N Engl J Med 2000;343:94-
99. Application of the NEXUS criteria.
mohammad reza rajabi
Page 38 4/3/2012