DEPARTMENT OF ANESTHESIA
UNIVERSITY OF MANITOBA
Airway Training Module for
Para Professional Personnel
Preamble
The Department of Anesthesia at the University of Manitoba is committed to the
promotion of patient safety and quality of care. Education of providers of airway and
resuscitation support from all disciplines is a fundamental part of that mission. For this
educational effort to be effective, it is important to consider and incorporate the particular
needs of each group for whom skills development is contemplated. This document
outlines the structure, and goals and objectives of a program designed to meet the
developmental needs of paramedical personnel providing care for patients with respect to
airway support.
Program Outline
Each trainee will be provided with a program outline, including a reference manual,
orientation and contact information, and evaluation logs. At the end of the rotation, the
trainee will be expected to keep evaluation logs and provide them to the Coordinator of
the sponsoring program as proof of completion of the educational program.
The trainee will present to the assigned hospital OR suite on the first day of the rotation,
at the time and place indicated in the orientation manual. The senior resident or site
coordinator will direct the trainee to a primary staff person. This primary staffperson
shall
 Review the educational material with the trainee
 Provide resource discussion
 Evaluate the degree to which the trainee has met the knowledge objectives
 Record the results of that evaluation on the evaluation log
 Coordinate access to airway management techniques with him/herself, and other
staff as available
Each individual staff physician or resident who supervises airway management
techniques will
 Observe the trainee and provide formative feedback
 Evaluate the trainee’s competence with the technique
 Record the evaluation on the provided log
 As applicable review and evaluate elements of the curriculum as discussed with
the primary mentor
Goals and Objectives
By the end of this rotation, the trainee will be able to:
 Describe the indications for, contraindications to and complications of
o Direct laryngoscopy
o Endotracheal intubation
o Extubation
o Mask ventilation
o Positive pressure ventilation
 Correctly assess adequacy of ventilation
 Correctly identify airway obstruction, and provide a differential diagnosis
 Describe the appropriate sequence of events required to relieve airway obstruction
 Describe the correct approach to a situation in which intubation is planned but
fails
 Describe the implications of barometric pressure changes for airway management
and ventilation, and appropriate interventions
 Describe the correct interpretation of information from a pulse oximeter,
including sources of error
 Demonstrate the proper technique of
o Mask ventilation, including jaw thrust and oral airway
o Direct laryngoscopy and intubation
o Confirmation of endotracheal tube placement
o Securing an endotracheal tube for transport
Evaluation Log for Paramedical
Airway Training Module
Major
Omissions
Minor
Omissions
No
Omissions
Complete
Discussion
Outstanding
o Direct laryngoscopy
o Endotracheal intubation
o Extubation
o Mask ventilation
o Positive pressure ventilation
Correctly assesses adequacy of ventilation
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Correctly identifies airway obstruction, and
provides a differential diagnosis
Describes the appropriate sequence of events
required to relieve airway obstruction
Describes the correct approach to a situation in
which intubation is planned but fails
Describes the implications of barometric pressure
changes for airway management and ventilation,
and appropriate interventions
Describe the correct interpretation of information
from a pulse oximeter, including sources of error
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Major
Errors
Minor
Errors
Competent
technique
Efficient
technique
Outstanding
Mask ventilation
Confirmation of endotracheal tube placement
Securing an endotracheal tube for transport
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Laryngoscopy #1
Laryngoscopy #2
Laryngoscopy #3
Laryngoscopy #4
Laryngoscopy #5
Laryngoscopy #6
Laryngoscopy #7
Laryngoscopy #8
Laryngoscopy #9
Laryngoscopy #10
Laryngoscopy #11
Laryngoscopy #12
Laryngoscopy #13
Laryngoscopy #14
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Cognitive Objectives
Describes the indications for, contraindications to
and complications of
o
Technical Skills Objectives
Airway Management
Gerry Bristow , MD FRCP
Rob Brown, MD FRCP
Proper airway management is the most fundamental step in the provision of life
support. Effective respiration is necessary for any other bodily function to occur, and
without it, any efforts to treat other problems will be in vain. This is well reflected in the
priority placed on assessment of the airway and adequacy of respiration in the acute care
protocols learned in the ACLS and ATLS courses. It is important to stress, however, that
airway management is not confined to the resuscitation of critically ill or injured patients.
It begins with attention to the status of the airway in any patient, in order to predict and
prevent the occurrence of problems.
In anesthesia, we deal with the management of airways on a daily basis.
Sometimes the need for airway management comes in the form of a patient who arrives
with airway pathology. More commonly, it is simply the physiologic impact of the
anesthetic itself that necessitates airway management. Whatever the cause, the goals of
airway management remain the same: the provision of a patent, secure airway; protection
of the lungs from aspiration; and maintenance of adequate gas exchange.
Airway Assessment
The first goal in assessing the upper airway is to identify any conditions that may
threaten the integrity of the airway. The assessment of upper airway obstruction will be
dealt with later in this chapter. Most patients presenting for elective procedures do not
have airway pathology, but still need airway assessment for another reason.
The second reason to assess an airway would be to predict the likelihood of
difficulty with managing the airway should that become necessary. Inducing anesthesia
and being unable to control the airway is a potentially life threatening event, and can
usually be predicted and prevented. There is a spectrum of difficulty that ranges from
easy to impossible. Moderate difficulty is relatively common, while impossible
intubations are rare. As the difficulty of laryngoscopy increases, so does the likelihood of
and severity of injury related to laryngoscopy. It has been estimated that ~30% of deaths
attributable to anesthesia are related to airway mishaps.
Table 1, Likelihood of Difficult Intubation
Degree of Difficulty
Successful- multiple attempts
Successful- multiple attempts and laryngoscopists
Not successful- ventilate by mask
Can’t intubate-can’t ventilate- cricothyrotomy, TTJV or death
Incidence
100-1800
100-400
5-35
.01-2
Modified from Benumof, J. “ management of the Difficult Airway”, Anesthesiology, 75(6):1087-1110, 1991
%
1-18
1-4
.05-.35
.0001-.02
The incidences above were generated from an anesthesia data base, and thus
would reflect the risk with a relatively high skill level in intubation as well as assessment.
It would not include those that were recognized by appropriate evaluation and managed
by other means.
Any patient with an obvious anatomic distortion of the airway, or with ongoing
airway obstruction should be considered to have a difficult airway, and managed
accordingly. This will be expanded upon later in this chapter. Many patients present with
no pathology, but may be difficult to intubate simply due to their anatomy. A careful
airway assessment will help you to identify the majority of those.
The examination of the airway with a view to ease of intubation involves
inspection of internal dimensions, external dimensions and range of motion. This has
been reviewed recently, focussing on three main predictors of difficult intubation: the
Malampati score; depth of the mandible; and neck extension.
The Malampati Scoring System
The scoring system developed by Malampati attempts to describe the size of the
soft tissues in the floor of the mouth relative to the mandible. Patients with a relatively
smaller submandibular space will be less able to depress the floor of the mouth to expose
the tonsillar pillars. Similarly, with direct laryngoscopy, one is attempting to depress the
floor of the mouth into the submandibular space to expose the glottis. Thus, inability to
visualize the posterior pharynx correlates with inability to visualize the cords. To
generate the Malampati score, have the patient sit upright, open his mouth and stick out
his tongue, with the neck in a neutral position. Without saying ”ah” try to get him to
depress the base of the tongue as much as possible. The score is based on the amount of
the pharynx you can see, (Fig 1). The table 2 shows the increasing likelihood of difficulty
with laryngoscopy with increasing Malampati score.
Fig.1 Malampati Score
From Benumof, J.,“Management of the Difficult Airway”, Anesthesiology 75:1087-1110, 1991
Table 2: Prediction of Difficult Intubation with Malampati Scoring
Malampati
Laryngoscopy Grade
Score
Visibility of
Grade 1
Grade 2
Grade 3
Grade 4
Structures
Class 1
59.5 %
14.3%
----( 73.8%)
Class 2 + 3
5.7%
6.7%
4.7%
1.9%
(19%)
Class 4
--0.5%
4.3%
2.4%
(7.14%)
Modified from Malampati, S,” A Clinical Sign to Predict difficult tracheal intubation: a prospective study”, Can Anesth Soc J,
32(4):429-34, 1985
Depth of the Mandible
The length of the mandible is another index of the size of the submandibular
space. Patients with a small mandible are more likely to be difficult to intubate. Different
approaches have been advocated to this measurement, including clinical or radiologic
measurement of the distance from the
hyoid to the angle of the jaw, and
Fig 2
measurement of the distance from the
thyroid cartilage to the mentum. The
most often used is the hyo-mental
distance. This is the distance from
the tip of the chin (mentum) to the
anterior surface of the hyoid bone. A
hyomental distance of less than 5 cm
correlates
with
an
increased
likelihood of difficult intubation.
This has two limitations. Very few
clinicians want to carry a ruler with
them. More importantly, this is really
intended
to
be
a
relative
measurement.
(A
hyo-mental
distance of 6cm in seven foot tall
patient
would
certainly
be
inadequate!) A convenient alternative
measurement
is
to
use
fingerbreadths.
A
hyo-mental
distance of less than 3 fingers
correlates with difficulty. In the case
of a patient who is not an average
sized adult, one can use the patients’
fingers to give an estimate relative to
his own body habitus.
Neck Extension
The ideal position for
intubating is the “sniff” position (fig
2). This refers to flexion at C7-T1, combined with
extension at C1-2. It is not uncommon for people
to have limitations of extension at C1-2. Neck
extension is a movement involving multiple
joints, and it is possible to make up for the lack of
mobility at C1-2 by extension at the other levels
of the cervical spine. From the point of view of
ease of laryngoscopy, it is, therefore, very
important to examine extension at C1-2 specifically. Watch from the side while a patient
extends the c-spine. The amount of extension can be measured by looking at the occlusal
surface of the upper molars (see Fig 3). A normal range of motion at C1-2 is from 0-35o.
Fig 3
A review of the above three airway measurements by Benumof showed that they
are highly predictive of difficulty with laryngoscopy. Used in combination, they should
allow the detection of 99% of difficult airways. Although important, these are not all of
the characteristics of an airway that might be relevant to the ease of laryngoscopy.
On examination of the oropharynx, prominent, loose, capped or missing teeth, or
a narrow or cleft palette would be indicators of possible difficulty. The presence of dental
prostheses should be noted. Laryngoscopy is best done with the prosthesis out, but in
some cases, ventilation by face mask can be difficult in the edentulous patient, due to the
loss of the normal facial contour for which the mask is designed. In these cases, it may be
easier to ventilate with the prosthesis in place, keeping in mind that the prosthesis also is
a foreign body, with the potential to dislodge and obstruct!
Two other ranges of motion that are important are mouth opening and anterior
displacement. Mouth opening can be measured in a manner similar to that described for
hyo-mental distance. A patient should be able to get 2 fingers between his incisors. The
inability to anteriorly displace the mandible far enough so that the lower incisors are
anterior to the uppers is also a concern.
Management of Upper Airway Obstruction
Identification
The identification of an obstructed upper airway is the first step in management.
One starts with searching for signs or symptoms of ongoing airway obstruction. This may
be due to structural abnormalities of the airway, or inability to maintain a structurally
normal airway for any reason. The priority is to determine the patency of the airway, then
deal with the underlying cause.
Even with a relatively mild degree of obstruction, most patients will complain of a
sensation of increased resistance to breathing, or suffocation. As the degree of obstruction
increases, this gives way to air hunger. The sensation of airway obstruction is very
distressing, and most patients experience fear, often to the point of panic. In an acute
upper airway obstruction, such as a foreign body, the typical posture of clutching the
throat and leaning forward is usually observed (fig 4).
Physical findings that suggest airway compromise
include: tachypnea, tachycardia, hypertension, use of
accessory muscles, nasal flaring, intercostal and suprasternal
indrawing, and decreased air entry. Several different sounds
are associated with the obstructed airway. The classic upper
airway sound is inspiratory stridor. This is a high-pitched,
wheezing, which must be distinguished from the wheezing of
lower airway obstruction, which occurs in expiration. Other
sounds may include snoring, in the case of obstruction by the
tongue. This occurs most commonly in patients with a
depressed level of consciousness, although it may be found in
patients with muscle weakness or a swollen pharynx. As with
lower airway obstruction, sounds only occur if there is
passage of air, and as obstruction worsens, any abnormal
Fig 4
sounds may become attenuated.
Many patients without obstruction at presentation are at risk of developing
obstruction due to a progressive lesion. This would include mass lesions (tumour), edema
(anaphylaxis, burns, epiglottitis), abcsess, hematoma, and airway trauma. In any patient
with pathology of the upper airway, one must consider whether it is a progressive lesion,
and if so, at what rate it can be expected to progress. Further investigations, such as
lateral neck x-rays, CT scans, or flow-volume loops, may be undertaken if it is judged
that there is no immediate risk to the airway. If, however, the airway integrity is
compromised, the establishment of a secure airway takes priority over further evaluation.
Mechanisms/Causes of Upper Airway Obstruction
There is a myriad of causes of upper airway obstruction. The upper airway can be
considered to extend from the teeth and nares to the thoracic inlet. The manifestations of
all obstructions above the thoracic inlet (extrathoracic) are similar in that the obstruction
worsens during inspiration, when intraluminal pressure decreases relative to extraluminal
or ambient pressure. This gives rise to the characteristic inspiratory stridor. In contrast,
with intrathoracic obstruction, negative intrathoracic pressure distends the airways on
inspiration, and positive intrathoracic pressure compresses them on expiration. Thus,
intrathoracic airway obstruction is characterized by predominantly expiratory wheeze.
Both types of obstruction progress to involve both phases of respiration as they become
severe.
Obstruction of the upper airway can be either mechanical, as in the case of airway
pathology, or functional, as in the case of depressed level of consciousness or neurologic
deficit. Different classification schemes are available, and the most important thing in the
emergency situation is to have an organized approach. A useful system is to consider the
possible causes at each anatomic level proceeding from intraluminal to extraluminal.
Level
Oropharynx
Structure Involved
Intraluminal
Soft tissue
Tongue, peritonsillar,
Uvula
Glottis
Subglottic
Cause
Foreign body
Tumour
Laxity (paralysis,  LOC)
Edema
Abscess
Hematoma
Congenital anomaly
Extrinsic
Abscess,
Tumour,
Hematoma
Intraluminal
Foreign body
Tumour
Epiglottis
Edema (epiglottitis)
Tumour
Trauma
Aryepiglottic folds,
Edema
Trauma
Tumour
Vocal
Cords/arytenoids
Structural (Edema, trauma)
Mobility (arthritis, dislocation)
Spasm
Intraluminal
Foreign body
Tumour
Web
Trachea
Edema
Tracheomalacia
Fracture/disruption
Stenosis
Extrinsic
Tumour
Hematoma
Thyroid
Treating Upper Airway Obstruction
The basic principles governing the management of unobstructed airway are the
same for all obstructed airways. The underlying cause, although important in determining
ultimate definitive therapy, is not the primary concern. The initial management is
determined by the degree of obstruction, with the goal of maintaining oxygenation.
The first step in the management of airway obstruction is to recognize it, as
discussed above. In any patient presenting with some symptoms or signs of airway
obstruction, the first step is to provide oxygen. The next step is to achieve sufficient
patency to allow for adequate respiration. One does this by progressing through a series
of maneuvers. In an awake patient who is already making maximal attempts to open his
own airway, airway resistance can be reduced by breathing a mixture of helium and
oxygen. Gentle positive pressure coordinated with spontaneous breaths will counteract
the negative intraluminal pressure of spontaneous breathing and thus help to distend the
airway.
In a patient with impaired airway control, or if the above is ineffective, proceed to
try to support the airway physically. Begin with positioning in the sniff position (see
above). Often, applying a face mask with gentle neck extension will relieve obstruction
by the tongue. Beware, if there is any possibility of c-spine injury, the neck should not be
extended! The next step is to perform a jaw thrust with one hand, then two hands if
needed. If this is unsuccessful, then an oral or nasal airway may be inserted. If this fails,
sometimes a two-person jaw thrust will alleviate the obstruction. This done by having a
second rescuer stand at the patient’s side and augment the jaw thrust by applying anterior
pressure to the angle of the jaw along with the first rescuer.
If none of these techniques is successful in providing patency, it will be necessary
to instrument the airway. This usually means intubation (see below), but there are other
adjuncts that may be useful as bridge to intubation. It cannot be overemphasized that, in
this situation, time is critical. At this point, pick the method you are best at. These other
adjuncts in inexpert hands often only have the ultimate effect of delaying control.
Larygeal Mask Airways (LMA)
The laryngeal mask airway is a large cuffed oral airway (fig 5). It is
designed to be inserted so that it sits on the glottic opening. The cuff is then blown up,
lifting the glottis off the posterior pharynx. This leaves the opening of the tube directly
above glottis. It is very useful in maintaining an unintubated airway while keeping your
hands free. It does not, however, provide a secure airway. There is no protection from
esophageal contents, nor any prevention of laryngospasm. In situations where it is
impossible to intubate or ventilate, it may provide an airway until such time as definitive
management can be completed.
Fig 5
From Clinical Anesthesia, Barash,P., ed., 2nd Ed, Lippincott
Esophageal Obturator/ Combitube
The
esophageal
obturator airway is similar to the
LMA, except that it has a cuffed
extension below the pharyngeal cuff.
It is designed to be blindly inserted
into the esophagus until the upper
cuff rests on the glottis, as with an
LMA. The lower cuff is then inflated,
occluding the esophagus, and the
upper cuff inflated sealing the
pharynx to allow for positive pressure
ventilation. The advantage over a
LMA is that it should provide some
measure of airway protection. The
disadvantage is that if it goes into the
trachea instead of the esophagus, it
will completely obstruct the airway.
The combitube is a refinement of the
obturator (fig 6). It is similar, except
that the extension has a lumen, giving
it a proximal and a distal lumen. It is
blindly inserted, and if the distal
lumen enters the esophagus, it
functions exactly as an obturator. If
the distal lumen enters the trachea,
however, it functions as an
endotracheal tube, albeit a bit bulky. The advantage is that it requires very little skill to
insert. The disadvantage is that it is often difficult to tell in the emergency situation,
whether the lumen is in the trachea or the esophagus, and one must be careful to
differentiate
Fig 5
Med, 22:10, 1573-75,
Transtracheal Jet Ventilation
An alternative to a surgical cricothyrotomy for emergency oxygenation is needle
cricothyrotomy. It is simple, fast, and relatively atraumatic. Jet ventilation is done by
giving brief ~ ½ second bursts of O2 at a rate of 20-60 per minute. When connected to a
high pressure (>18psi) O2 source, it will allow adeqaute oxygenation for a long period of
time, with reasonable CO2 removal. Adequate ventilation cannot be achieved with low
pressure O2, although it will provide some oxygenation. The important caveat when
using TTJV is to ensure there is egress of air. If not, the high pressure O2 source will
rapidly cause high intrathoracic pressures, leading to severe and potentially fatal
barotrauma.
Tracheal Intubation
Indications
There are many different situations in which intubation of the trachea is indicated.
One could simply make an exhaustive list of the individual indications. As discussed in
the section on airway obstruction, it is important in the emergency situation to have an
organized approach to the question of endotracheal intubation. An endotracheal tube can
perform three basic functions. It can provide airway maintenance, protection, and
positive pressure ventilation. Thus, the indications for intubation would be: risk to airway
patency; risk of airway contamination; or need for positive pressure ventilation.
When airway patency is already compromised, the need for intubation is usually
obvious. Equally important is the need to predict impending airway obstruction, as
discussed above. Prophylactic intubation may be indicated in these conditions. Patients
presenting obstructed due to level of consciousness are usually easily supported by mask,
but it may be hours before their ability to maintain their own airway returns, if at all. It
may, therefore, be expedient to intubate a patient whose airway is supportable by mask,
to free yourself for other activities.
Indications for endotracheal intubation
Airway maintenance
Obstruction
Potential Obstruction
Prolonged airway support
Airway protection
Impaired airway reflexes and
Potentially aspiratable material
Blood, pus, stomach contents
Respiratory failure
Hyperventilation ( ICP)
Paralysis (anesthetized)
Positive pressure ventilation
An airway needs to be protected when there is some risk of contamination. Two
conditions must be met for there to be such a risk. First, there must be something to
contaminate the airway. Any patient presenting in an emergency situation will have a full
stomach, and thus has the potential for regurgitation and aspiration. Other materials that
present the potential for aspiration include blood, pus or foreign body. Secondly, there
must be some impairment of airway protective reflexes. With intact reflexes, a patient
should be able to prevent the contamination of the airway. Reflexes may be impaired by
level of consciousness, sensory, or motor abnormalities.
Positive pressure ventilation is indicated for treatment of respiratory failure. There
are many underlying disease states that may ultimately end in respiratory failure. This
section will not expand on these, nor the management of positive pressure ventilation,
except in so far as to deal with the decision to intubate. Respiratory failure itself may be
either hypercapnic, hypoxic, or a combination. The precise point in time at which
intubation is required in the setting of respiratory distress is a clinical decision.
Hypercapnia and/or hypoxia do not warrant intubation on their own merit unless severe.
Additional factors may precipitate the decision to intubate in milder
hypercapnia/hypoxia. Progressive deterioration, or signs of fatigue would suggest that the
patient will ultimately fail and should likely be intubated while there is still some reserve
left.
Techniques of Tracheal Intubation
There are many different ways to intubate the trachea. In choosing a technique,
there are three basic decisions to be made. The first is whether to intubate awake, or after
inducing anesthesia. The second is which route to use, oral, nasal, or transtracheal. The
third is. whether to use a blind or visualized technique. This section will provide a
general discussion of these choices. The mechanics of intubation will be taught during the
clinical sessions in the OR. An in depth discussion of intubation techniques can be found
in any basic anesthesia text.
Probably the most important decision to be made is whether to intubate the patient
awake or not. In elective anesthetics, by far the most common approach is to intubate
after the induction of anesthesia, unless there is a reason not to. This is because intubation
awake, although safer, is unpleasant. When deciding whether to intubate asleep, there are
three conditions that must be satisfied. First, you must be confident that you will be able
to intubate this patient. The greatest risk of inducing first is that it may prove impossible
to intubate the now apneic patient. If it also proved impossible to ventilate, that would be
fatal. You can be confident that you will be able to intubate if, 1) you have sufficient
skill, equipment and assistance and, 2) a thorough assessment of the patient shows no
reason to suspect difficulty. Secondly, the patient must be able to tolerate apnea. When
an induction is done, the patient will be rendered apneic. If it is not possible to adequately
oxygenate the patient prior to induction, this apnea will lead to rapid and profound
hypoxia. Finally, the patient must be able to tolerate the cardiovascular impact of
induction. The drugs used to induce anesthesia all have cardiovascular depressant
properties. Any patient, who starts out unstable hemodynamically, is at risk of collapse
with induction. Considering these principles, it is not surprising that most emergency
intubations are done awake, as they usually satisfy one or all the criteria.
The decision of which route to use must consider the relative advantages and
disadvantages of each. The oral route is the most common, having the advantage of ease,
familiarity, the ability to see and assess the glottis, and avoidance of the specific
problems of the others. There are a few disadvantages of the oral route. It is sometimes
impossible due to anatomic obstacles. It is very difficult in an uncooperative patient to
the point of being impossible if the patient will or can not open his mouth.
The nasal route allows one to bypass several of the shortcomings of the oral route,
and is commonly learned as a second line method. It is less affected by cooperation. It is
also possible with a closed mouth. Similarly, it allows better access to the oropharynx,
and the ability to close the mouth with the tube in, which can be important in oral
surgery. There are several disadvantages that limit its use as a first line method. It is more
uncomfortable if done awake, causes epistaxis, predisposes to sinusitis, and is
contraindicated in basal skull fracture or anatomic obstruction of the nares. It is also
impossible to do entirely under direct vision, although partially visualized techniques
may be used. For this reason, it is generally not advisable in management of airway
abscesses.
The direct transtracheal or transcricothyroid route is not commonly done, but has
a very definite role. The main advantage is that it allows one to bypass any pathology
above the glottis, thus allowing access in most situations of difficult intubation. It is,
therefore, the backup method for the situation when other methods have failed. It should
be learned by anyone who expects to intubate as part of their practice (anesthesia, ER,
ICU, rural). It also has the advantage of requiring less neck movement, and in some
centers is used as the first line approach to the airway in c-spine injuries. The obvious
disadvantage is the need for a surgical incision and the attendant risks of bleeding,
infection, and damage to local structures. It is relatively contraindicated in patients with
coagulopathy, infection or tumour at the site, or anatomic distortion at the site. The
contraindications are relative, in that it may be necessary anyway, if there are no other
options available, to alleviate airway obstruction, which would otherwise be fatal.
The decision of blind, visualized, or partially visualized will depend partly on the
route chosen, as well as other factors. Direct visualization has the advantage of the best
degree of certainty as to tube placement, as well as inspection of the glottis. It is also
generally the fastest and easiest. The disadvantage is that it is not always possible, and, in
an awake patient, is more uncomfortable. The blind or partially visualized techniques do
not require the same degree of manipulation of the airway, and although more technically
demanding, may be less uncomfortable. More importantly, they can often result in a
successful intubation when the direct approach is impossible. Which method is ultimately
selected is most often limited by the methods at which the clinician is skilled.
Anesthesiologists are skilled in a wide variety, but it is uncommon for clinicians outside
of anesthesia to be skilled in more than two or three different techniques.
Complications
The complications of intubation relate to damage during insertion, as well as
damage from the presence of the tube over time. Damage that can occur during insertion
includes trauma to the lips, teeth, tongue, oro- and nasopharyngeal soft tissues, cords,
arytenoids, amd trachea. This may manifest as local laceration and bleeding, which is
generally short-lived. Damage to the arytenoids and cords may cause premanent voice
changes. It is also possible to jeopardize airway patency with an expanding hematoma, or
the creation of a false lumen, as in the case of tracheal mucosal laceration. A less obvious
vulnerable structure is the eyes, and corneal laceration is one of the most common
injuries related to anesthesia.
Complications of long-term intubation are due to the mechanical irritation of the
tube in the trachea, as well as its interference with normal tracheal physiology. Tracheal
stenosis is the result of local irritation and ischemia. The main contributor to risk is the
duration of intubation. After several days the risk of stenosis becomes higher, and after 710 days, if it seems that the tube will not be out soon, tracheostomy is often done. Other
contributors to this risk are larger tubes and high pressures in the cuff. Endotracheal tubes
also interfere with normal mucociliary function, and may contribute to the development
of pneumonias. This presents the clinical dilemma that they may be needed to support
ventilation while at the same time contributing to the deterioration in overall pulmonary
status.
Difficult Intubations
The purpose of airway assessment is to identify the likelihood of difficult
intubation, as outlined above. If it is deemed likely hat an intubation will be difficult, as
discussed in the section on intubation, it should be done awake if at all possible.
Intubating a patient awake involves first anesthetizing the airway. The extent to which
this is possible will depend on the urgency of the situation, as well as the skill of the
clinician. It is a time-consuming, and technically demanding procedure. Appoaches to
freezing an airway range from simple spray topicalization ( the most common, and least
effective) to special topical techniques and injection techniques. The use of sedation is a
very common, and potentially catastrophic practice Awake intubations with poor
topicalization are unpleasant. The solution is to improve the topicalization. The all too
common response of giving sedation in this situation can quickly lead to disaster. The
patient will usually become disinhibited, and struggle even more. Further sedation will
result in a patient who is awake enough to fight off intubation, but too sedated to breathe
effectively, especially since they likely couldn’t in the first place! If sedation is to be used
at all, it should be with great caution, and with reversible agents. As depicted in the
algorithm on difficult intubation, there will be occasional situations when it is truly
impossible to intubate awake. In these, it is better to completely induce the patient than to
wander into the semi-anesthetized realm described above. Induction in this situation
should only be undertaken by an expert in airway management, and with preparation for
immediate surgical airway.
Unfortunately, even with the most conscientious airway assessment, there will
still be occasions when a patient will be induced and then turn out to be difficult to
intubate. There are also situations where the patient may present already unconscious,
needing intubation. Either of these is a life-threatening event. The time frame available to
deal with such an event is, at best, a few minutes. After that time brain damage or death
become increasingly likely. This is, obviously, a very stressful situation. The key to
management, as with all emergency situations, is to have a protocol ready ahead of time.
This is the same philosophy applied in ACLS and ATLS. Although this situation is
incredibly intense and stressful, the problem at hand is very simple. Keeping that in mind
and going through the steps in an organized manner will mean the difference between life
and death. The American Society of Anesthesiologists has published a very useful
algorithm for the management of the difficult airway. The theme to the whole algorithm
is to maintain a focus on ventilation (see Fig 7).
The entry point to the algorithm is the recognition that you have a difficult
intubation. One of the most common errors is to persist with initial attempts at intubation
prior to realizing or admitting that you are in trouble. If, after one attempt, you are unable
to intubate, search for immediately correctable causes (too small a laryngoscope blade,
poor positioning etc). If there is something obviously causing the problem, it is
reasonable to correct it and try again once, providing that the patient is well saturated. If
the saturation is already falling, there is no obvious correctable cause, or the second
attempt fails, immediately attempt to ventilate the patient. Proceed through the series of
airway maneuvers as outlined in the section on the obstructed airway. There are only two
possible outcomes at this point. You will either be able to ventilate or not.
If you cannot ventilate, proceed directly to airway instrumentation. For most
situations, the method of choice will be cricothyrotomy. Legitimate alternatives would
include needle cricothyrotomy, or LMA, with the proviso that they are immediately
available. Equipment for cricothyrotomy should be available in all intubating locations,
but the equipment for TTJV and LMA are rarely available outside of ORs. There is no
time to look for equipment at this stage, and unless you have checked beforehand, they
are not options.
The second, more favourable outcome would be that you are able to ventilate. The
first thing to do is to apply cricoid pressure, and to take a moment to calm down. There is
no immediate threat to life, and injudicious action at this point may change that. The
question at this point is how urgently intubation is required. It may be feasible to simply
ventilate the patient until he is awake, and proceed with an awake intubation. This may
not be a realistic option, either due to the need to proceed with a surgical procedure, or
because the patient is not expected to awaken. If that is the case, try to wait for expert
assistance. If that is not available proceed with whatever other techniques are available at
which you are skilled. The most important thing to remember at this point is that
whatever other technique is used, it must be done gently. Persistent attempts to intubate
will inevitably traumatize the airway, resulting in progressive edema, bleeding and
eventual obstruction. Then you’re back in the can’t intubate, can’t ventilate scenario.
Fig 7: The ASA Difficult Airway Algorithm