This document provides information on predicting and evaluating difficult airways. It defines different types of difficult airways including difficult bag mask ventilation, difficult supraglottic airway device insertion, and difficult endotracheal intubation. Risk factors for difficult bag mask ventilation include age over 55, BMI over 26, facial hair, being edentulous, and a small thyromental distance. The Mallampati score and measurements of mandibular space can help predict difficult direct laryngoscopy. A full airway examination involves assessing the patient's history, mouth opening, neck mobility, jaw movement, and nasal patency.

1. AIRWAY SKILL
STATION
INTRODUCTION

2. Definitions
Airway:
– The passage through which the air passes during respiration.
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

3. Difficult Airway
The difficult airway should be defined in terms
of the key components of airway management.
1 Bag-mask ventilation
2 Supraglottic airway insertion
3 Tracheal intubation
4 Infraglottic airway insertion

4. Difficult mask ventilation

5. Difficult mask ventilation
❖ As the inability of the unassisted anaesthetist to
maintain the saturations (SpO2) above 90 per
cent using a FiO2 of 100 per cent and positive
pressure ventilation where the patients’
saturations were above 90 per cent prior to
intervention or the inability of said anaesthetist to
prevent or reverse the signs of inadequate
ventilation during positive pressure ventilation.

6. Difficult mask ventilation
Han’s mask ventilation grading scale.
Grade 1 Ventilated by mask
Grade 2 Ventilated by mask plus oral airway
adjuvant +/-muscle relaxant
Grade 3 Difficult to mask ventilate despite above,
inadequate or unstable, requiring two
providers
Grade 4 Unable to mask ventilate with or without
the use of muscle relaxants.
Han R, et al. Grading scale for mask ventilation. Anesthesiology, 2004. 101(1): pp. 267.

7. PREDICTORS OF DIFFICULT BAG-MASK
VENTILATION
Factor Odds ratio (95% CI) P value
Age >55 2.26 (1.34-3.81) 0.002
BMI >26 kg.m-2 2.75 (1.64-4.62) <0.001
Facial hair (beard) 3.18 (1.39-7.27) 0.006
Edentulous 2.28 (1.26-4.10) 0.006
Langeron’s independent risk factors for difficult mask ventilation

8. PREDICTORS OF DIFFICULT BAG-MASK
VENTILATION
Kheterpal and colleagues risk factors for
difficult (grade 3) mask ventilation

9. PREDICTORS OF DIFFICULT BAG-MASK
VENTILATION
Kheterpal and colleagues risk factors for
difficult (grade 4) mask ventilation.

10. PREDICTORS OF DIFFICULT BAG-MASK
VENTILATION
Murphy and Walls’s difficult bag-mask
ventilation mnemonic: MOANS.

11. DIFFICULT LARYNGEAL MASK
VENTILATION

12. DIFFICULT LARYNGEAL MASK
VENTILATION
❖Difficult laryngeal mask ventilation has been
defined as the inability to, within three
insertions, place the laryngeal mask in a
satisfactory position to allow clinically
adequate ventilation and airway patency.
Clinically adequate ventilation was defined as
greater than 7ml.kg-1 with a leak pressure no
greater than 15-20cm H2O pressure.

13. PREDICTION OF DIFFICULT SUPRAGLOTTIC AIRWAY DEVICE
INSERTION
Murphy and Walls’s difficult supraglottic device insertion mnemonic: RODS.

14. Difficult Endotracheal Intubation

15. Difficult endotracheal intubation
Difficult endotracheal intubation
– The ASA originally defined difficult intubation as
requiring more than three attempts or taking
longer than 10 minutes to complete

16. Murphy and Walls’s bedside predictors of difficult intubation
with direct laryngoscopy.

17. Modified Cormack and Lehane classification.

18. EVALUATION OF THE
AIRWAY

19. 1. History
2. Physical examination

20. Physical examination:
A global assessment should include the
following:
• Patency of nares : look for masses inside nasal
cavity (e.g. polyps) deviated nasal septum,
etc.
• Mouth opening of at least 2 large finger
breadths between upper and lower incisors in
adults is desirable

21. Physical examination:
• Teeth : Prominent upper incisors,an
edentulous state.
• Palate : A high arched palate or a long, narrow
mouth.
• Prognathism.
• Temporo-mandibular joint movement
• Measurement of submental space
• Presence of hoarse voice/stridor or previous
tracheostomy.

22. Physical examination:
Specific tests for assessment:
Anatomical criteria
1) Atlanto occipital joint (AO) extension
• Grade I : >35°
• Grade II : 22°-34°
• Grade III : 12°-21°
• Grade IV :<12°

23. Physical examination:
Specific tests for assessment:
MALLAMPATTI TEST

24. Physical examination:
Specific tests for assessment:
Mandibular space
1.Thyromental (T-M) distance (Patil’s test): Alignment of axes is difficult if the
T-M distance is < 3 finger breadths or < 6 cm in adults; 6-6.5 cm is less
difficult, while > 6.5 cm is normal.
2.Sterno-mental distance : A value of less than 12 cm is found to predict a
difficult intubation.
3.Mandibulo-hyoid distance

25. Six standards in the evaluation of airway
1) Temporomandibular mobility – One finger
2) Inspection of mouth, oropharynx – Mallampati classification – Two fingers
3)Measurement of mento-hyoid distance (4 cm) in adult– Three fingers.
4)Measurement of distance from chin to thyroid notch – (5 to 6 cm)– Four fingers
5)Ability to flex head towards chest, extend head at atlanto-occipital junction and
rotate head, turn right and left (five movements).
6) Symmetry of nose and patency of nasal passage.