Airway assessment is important for identifying patients at risk of a difficult airway. Several tests can be used including Mallampati scoring, mouth opening, neck mobility, and thyromental distance. A difficult airway is when facemask ventilation or intubation is not possible using conventional methods. It is important to prepare for difficult airway scenarios by having proper equipment and involving senior help. Identifying difficult airway risks pre-operatively allows time for planning alternative strategies to ensure patient safety.

1. Airway Assessment In
Anaesthesia
By Dr Bhagya Perera

2. What is the Airway?
 ‘Airway’ refers to the normal passageway for air
entry and exit in a human being for efficient gas
exchange at the lungs.
 The airway includes the nose, mouth, pharynx,
larynx and trachea.
 Maintenance of Airway patency and continuous
gas exchange is of paramount importance in
general anesthesia.

3. What is a difficult airway?
 A difficult airway is defined as the clinical situation in
which a conventionally trained anesthesiologist
experiences difficulty with facemask ventilation of the
upper airway, difficulty with tracheal intubation, or both.
 The difficult airway represents a complex interaction
between patient factors, the clinical setting, and the
skills of the practitioner.
 Difficult tracheal intubation accounts for 17% of all
respiratory injuries and results in significant morbidity and
mortality due to respiratory injuries and hypoxia.

4. Statistics of Difficult Ventilation and Airway
Intubation:
 Difficult Ventilation: The event where a trained Anesthetist is unable to
maintain SpO2 at >90% on 100% inspired O2 via Facemask, provided Pre-
induction SpO2 levels were normal.
 Occurs in 0.1- 5% cases.
 Difficult Intubation: More than 3 attempts, Longer than 10 mins,
Optimal best attempt has failed.
 Difficult LMA – 0.2- 1% cases
 Difficult Intubation
 Normal Surgical Population: 1-2% cases
 Patients with compromised neck extension (RA, CS) : 40- 50%
cases

5. Goals of Airway Assessment
 To identify potentially difficult airway intubations prior to
surgery and anesthesia
 To identify possible risks associated with certain airway
intubations in individual patients
 To minimize the risk of respiratory events both intra and
post-operatively.

6. Methods of Assessment

7.  History
 Age
 Dentures/Loose teeth
 Snoring/ Sleep Apnoea
 Cervical Spine Abnormalities: RA, Cervical Spondylosis, Ankylosing Spondylosis
 Previous Surgeries in the neck : Tracheostomy/ Thyroidectomy
 Mandibular/ TMJ abnormalities: Prev Hemi-mandibulectomy, TMJ dysfunction
 Previous airway problems/ difficult intubations/ stenosis/ reaction to anaesthetics
 Examination
 Face: facial deformities : Receding chin, small submandibular space
 Teeth: Malocclusion overbite of anterior teeth
 Limited protrusion of the Mandible/ Limited mouth opening
 Loose teeth or dentures
 Large tongue
 Neck: Obesity, Short neck, Dorsocervical fat pad, Limited neck movement

8.  Airway Assessment TESTS: Always better to use a combination of tests
 Oropharynx
 Atlanto-Occipital Joint
 Submandibular Space

9. Oropharynx : Mallampati Test
 Aims: To assess mouth opening and tongue and pharyngeal size
 Relative assessment of view of pharynx
 Patient seated in neutral position looking directly ahead
 Ask Patient to open mouth wide and protrude tongue as far as possible
without phonation.
 Must be examined with eyes kept in line with the patient’s mouth.
 Findings are then compared against preset classification.

10. Mallampati Test: Classification
Back of
the
Pharynx

11. Atlanto-Occipital Joint Movement
Head and Neck Extension
 Head Extension at Atlanto-occipital joint and flexion at Atlanto-axial joint
brings the laryngeal and pharyngeal planes almost to a straight line
 This must be examined in the seated position to avoid error due to bowing of
the cervical spine.
 A neck extension of 35o degrees is considered normal.

12. Sterno-mental Distance
 The patient is asked to extend the neck and look at the ceiling and
the distance from the supra-sternal notch to the tip of the chin
(mandible) is measured.
 The critical distance is 12.5cm

13. Submandibular Space
- Thyro-mental distance
 With the patient’s head extended, the sub-mandibular space is measured by
the distance between the tip of the chin and the thyroid notch in cm or finger
breaths.
 Normal finding would be >6.5cm or >3finger breadths. <6cm is considered
difficult intubation.
 Smaller sub-mandibular space may mean obstruction of line of vision of
pharyngeal space.
 A Miller-blade may be preferred in laryngoscopy.

15. In the field: 3,3,2

17. Cormack-Lehane Direct Laryngoscopy
classification
Epiglottis
Vocal Cords
Arytenoids

19. LEMON RULE
 The LEMON rule allows us to remember to look externally and to look at those parameters that
will make the intubation simple or difficult.
 L.E.M.O.N stands for:
 L – Look externally – Is the patient obese, do they have a high arched palate, a short neck, facial
or neck trauma? Extensive beard?
 E – Evaluate the 3:3:2 rule – 3cm/finger breaths mouth opening, 3cm thyro-mental distance, 2cm
between hyoid bone and thyroid notch.
 M – Mallampati Score –a Mallampati Class 4 is associated with a >10% chance of difficult airway
 O – Obstruction – Is there a tumour, epiglottitis, recent neck surgery?
 N – Neck mobility – Is the patient in a cervical collar, are they elderly?

20. Wilson scoring
 Predicts difficult airway
intubations using five factors
 Each factor is scored between
0- 2
 A total score is calculated
between 0-10
 A higher score indicating a
higher incidence of difficulty
intubating the patient.
Factors
 Weight
 Head and Neck Movement
 Jaw Movement
 Receding Mandible
 Buck Teeth

21. What to do when suspecting a
Difficult Airway Intubation

22. What to do when suspecting a Difficult
Airway Intubation
 Get help. Confer with a senior colleague or Consultant Anesthetist.
Get advice on how to proceed with the intubation.
 Be ready for every case scenario
 Check and be prepared with the difficult intubation trolley
 Confer with Surgical team. Consider alternative methods or
anesthesia such as regional anesthesia (Ex Epidural, Spinal Anesthesia,
Local anesthesia)
 Consider Supraglottic Airway (LMAs)

23. Difficult Intubation Strategy
A: • Airway Management
B: • Breathing: Oxygenation and Ventilation
C:
• Continue Surgery/ Awaken and Postpone
D:
• Danger! CVCI Plan: Rescue Techniques
E:
• Extubation Strategy: Awake Extubation
F: • Follow up

25. Difficult Intubation Trolley
 Oro and nasopharyngeal airways of all sizes
 Laryngoscopes 2 – Batteries/ Light source checked
 Blades- 4 sizes, Mackintosh, Miller, Mc Coy blades, straight blades
 Endotracheal tubes many sizes
 Stylet and Bougie
 LMAs all sizes, ILMA
 Combi tube (blind insertion)
 Wee’s Oesophageal detector
 Video Laryngoscope
 Tracheostomy tube + Set
 Cricothyroidotomy Set

27. Take Home Messages
 Analyse all prospective GA patients for risk of difficult intubation.
Identifying the risk early gives Anesthetist time to anticipate and
prepare for the problem.
 If suspicious of possible difficult airway: Secure the airway while
awake.
 Not maintaining airway? Oxygenate and restore Spontaneous
breathing. Attempt to secure airway with more skilled personnel.
 Cannot ventilate Cannot intubate?: Move to Rescue measures.
 Follow up to ensure future procedures undergo proper risk assessment
of patient.

28. References
 British Journal Of Anesthesia – Oxford University Press Online Article Archive
 Handbook of Anesthesia- College of Anesthesiologists, Sri Lanka
 Practice Guidelines for Difficult Airway Management- American Society of
Anesthesiologists (Special Issue 2013)
 NCBI- NIH- US National Library of Medicine
 Elsevier Open Access Journals
 Smith and Atkinhead’s Textbook of Anesthesia
 East Midlands Emergency Medicine edu media.
 Resus Austrailia