Airway Assessment

CHANGING THE PARADIGM: THE NEXT STEP – WHAT, WHEN AND HOW?
Much of difficult airway practice is based on anaesthesia folklore, time-honoured techniques,
local expert opinion and a paucity of case reports. Devising a dictum for airway management
will always be controversial. The authors wish to stimulate discussion by outlining what they do
and teach. It is important to lay down an infrastructure for choosing the “right tool for the right
job”. The selection process is built on seven axioms. These are outlined in Table 1.
Table 1: The basis of a selection process for difficult airway devices for an anaesthesia
department.
Book of Proverbs, 9:1: “Wisdom hath builded her house, she hath hewn out her seven pillars.”
1. Oxygenation, not intubation, is the priority at all times.
2. The provision of difficult airway equipment should be for use by the least experienced
personnel and not the most experienced. Devices should be intuitive and user-friendly with
a short training period.
3. Devices should have sufficient reliable research to support their clinical role.
4. Rescue devices should have a high success rate to ensure the minimal number of steps
when securing the airway. A device with a high success rate in routine use may have
a lower success rate when used as a rescue manoeuvre, especially when the difficult
airway is unexpected. The urgency and the possibility of morbidity or mortality are likely to
negatively influence its success.
5. Devices should be trialled over an adequate period of time (several weeks in most cases)
to ensure that the device is used for a variety of airway problems and by an adequate
cross-section of staff.
6. Successful intubation should be followed by successful extubation. A range of tube
exchange catheters for use in difficult airway extubation should be available.
7. Provision of devices for oxygenation followed by technical and non-technical training is
mandatory for all areas where anaesthesia is conducted.
The two-curve theory provides an understanding of normal airway morphology and its variants.
The three-column model is a functional classification of difficult airways based on the various
steps taken during direct laryngoscopy and intubation. This classification then provides the
operator an understanding of the various causes of difficult airways and how they are related to
each other and airway morphology (two-curve theory). These two concepts form the basis for
understanding the problem at hand and allow the operator to devise a logical airway plan.
The following represents an extrapolation of the two-curve theory based on an airway
assessment employing the three-column model.
Posterior column pathology – normal anterior column
For example, manual in-line neck stabilisation (MILNS), ankylosing spondylitis and morbid
obesity.
Common issue: lack of extension of the upper cervical spine causing poor flattening of the
primary curve
49 Airway Assessment