This document discusses the importance of airway assessment prior to anesthesia. It defines a difficult airway as one where a trained anesthetist experiences difficulty with mask ventilation, tracheal intubation, or both. Components of airway examination are described, such as mouth opening, neck mobility, and Mallampati score. Predictors of difficult mask ventilation and intubation are provided. Specific tests are outlined to assess the oropharynx, hyomental distance, thyromental distance, and range of neck motion. Causes and prevalence of difficult airways are reviewed. The document emphasizes performing a thorough airway assessment to predict and prepare for potential difficulties.

1. Airway Assessment
Mohamad Hasnol Hayat

2. Airway
• The passage through which the air
passes during respiration
•  Nasal and oral cavities
 Pharynx
 Larynx
 Trachea and large bronchi

3. Why need to assess
• Respiratory events are the most common anaesthetic related injuries,
following dental damage. Three main causes:
• Inadequate ventilation
• Oesophageal intubation
• Difficult tracheal intubation
• Difficult tracheal intubation accounts for 17% of the respiratory related
injuries and results in significant morbidity and mortality.
• Estimated that up to 28% of all anaesthetic related deaths are secondary
to the inability to mask ventilate or intubate.
• Prediction of the difficult airway allows time for proper selection of
equipment, technique and personnel experienced in difficult airways

4. Difficult airway
•ASA definition of difficult airway:
“The clinical situation in which a
conventionally trained anaesthetist
experiences difficulty with mask
ventilation, difficulty with tracheal
intubation or both.”

5. Difficult ventilation
• The inability of a trained anesthetist to
maintain the oxygen saturation > 90% using a
face mask for ventilation and 100% inspired
oxygen, provided that the pre-ventilation
oxygen saturation level was within the normal
range.

6. Difficult intubation
 More than 3 attempts
 Longer than 10 minutes
 Failure of optimal best attempt

7. Prevalence
• Difficult face mask ◦ 0.1% - 5%
• Difficult LMA ◦ 0.2% - 1%
• Difficult intubation
•1-2% of normal surgical population
•50% of rheumatic cervical disease

8. Components of airway examination
• Nostril patency
• Length of the upper incisors, alignment
• Condition of the teeth
• Relationship of the upper (maxillary) incisors to the lower (mandibular) incisors
• Ability to protrude or advance the lower (mandibular) incisors in front of the upper (maxillary) incisors
• Interincisor or intergum (if edentulous) distance
• Tongue size
• Visibility of the uvula e.g. mallampati
• Presence of heavy facial hair
• Compliance of the mandibular space
• Thyromental distance with the head in maximum extension
• Length of the neck
• Thickness or circumference of the neck
• Range of motion of the head and neck
• Cheek pad

9. Causes of difficult airway
• Stiffness
◦ Arthritis of neck/ jaw/ larynx. ◦ Fixation devices
◦ Scleroderma
◦ Diabetes
• Deformity
◦ Cervical and craniofacial
◦Burns/trauma/infection
• Swelling
◦ Infection/ tumour/ trauma/ burns
◦ Anaphylaxis/ haematoma/ acromegaly
• Reflexes
◦ Cough/ breathholding
◦ Laryngospasm/ salivation/ regurgitation
 Foreign body
 Other–Pregnant/ full stomach

10. Airway
assessment
• History
• Patient/notes/chart/medic-alert/spam letter
• Difficulty
• Surgery/burns
• Concurrentdisease
• Reflux/recentmeals
• General examination
• Do they just look difficult?
• Dentition (prominent upper incisors, receding chin)
• Distortion (edema, blood, vomits, tumor, infection)
• Disproportion (short chin-to-larynx distance, bull neck,
large tongue, small mouth)
• Dysmobility (TMJ and cervical spine)
• Massively obese or pregnant
• Beards +/- tubes
• Specific tests/indices
• Investigations.
• Nasoendoscopy
• X-ray, CT/MRI
• Flow volume loop

11. Predictors of difficulty to bag mask ventilate
• The Obese (body mass index > 35 kg/m2)
• The Bearded
• The Elderly (older than 60 y)
• The Snorers
• The Edentulous
(=BONES)

12. Predictors of
difficult
laryngoscopy
and intubation
• Individual indices
• Physical examination indices
• radiological indices
• advanced indices
• Group indices
• Wilson‘s score
• Benumof‘s analysis
• Saghei & safavi test
• Lemon assessment
• Arne‘s simplified score
• Magboul‘s 4 M‘s

13. Atlanto occipital movement
• The patient is asked to hold head erect, facing directly to
the front, then he is asked to extend the head maximally
and the examiner estimates the angle traversed by the
occlusal surface of upper teeth.
• Visual assessment or using a goniometer.
• Grade I >35 degrees
• Grade II 22-34 degrees
• Grade III 12–21 degrees
• Grade IV <12 degrees
• Assesses feasibility to make the optimal intubation position
with alignment of oral, pharyngeal and laryngeal axes into
a straight line.
• Limited A-O joint extension
• Spondylosis, rheumatoid arthritis, halo-jacket fixation,
and in patients with symptoms indicating nerve
compression with cervical extension.

14. Prayer sign
• A positive "prayer sign" can be elicited on
examination with the patient unable to
approximate the palmar surfaces of the
phalangeal joints while pressing their hands
together.
• Seen in diabetes
• This represents:- cervical spine immobility
and the potential for a difficult endotracheal
intubation.

15. Palm print test
• The palm and fingers of the dominant
hand of the patient is painted with black
writing ink using a brush.
• The patient then presses the hand firmly
against a white sheet of paper on a hard
surface. Scoring is done as:
• Grade 0 - All phalangeal areas
visible.
• Grade 1 - Deficiency in the inter-
phalangeal areas of 4th and/or
5thdigit.
• Grade2 - Deficiency in the inter-
phalangeal areas of 2nd to 5th digit.
• Grade 3 - Only the tips of digits
seen.

16. Assessment of
TM Joint
• TM joint exhibits 2 function.
• Rotation of the condyle in the
synovial cavity.
• Forward displacement of the
condyle.
• First movement is responsible
for 2-3cm mouth opening
• The second is responsible for
further 2-3cm mouth opening.

17. Subluxation of TMJ
• Index finger is placed in front of the
tragus & the thumb is placed in
front of the the lower part of the
mastoid process. patient is asked
to open his mouth as wide as
possible. Index finger in front of the
tragus can be intented in its space
and the thumb can feel the sliding
movement of the condyle as the
condyle of the mandible slides
forward.

19. Assessment of mandibular space
• Can be expressed as thyromental and hyomental
space.
• This space determines how easily the laryngeal and
pharyngeal axis will fall in line when the a-o joint is
extended.

20. Thyromental
Distance
• Measure from upper edge of thyroid
cartilage to chin with the head fully
extended.
• Normalis approx7cm.
• If the thyromental distance is short, <3
finger widths, the laryngeal axis makes a
more acute angle with the pharyngeal axis
and it will be difficult to achieve
alignment. Less space to displace the
tongue

21. • Limitation
• Little reliability in prediction
• Variation according to height, ethnicity
• Modification to improve the accuracy
• Ratio of height to thyromental distance (RHTMD)
• Useful bedside screening test
• RHTMD > 23.5 – very sensitive predictor of difficult
laryngoscopy

22. Hyo Mental Distance
Distance between mentum and
hyoid bone
Grade I : > 6 cm
Grade II: 4– 6 cm
Grade III : < 4 cm – Impossible
laryngoscopy and Intubation

23. Interincisor gap
• Inter-incisor distance with maximal mouth opening
• Normal value > 5 cm / admits 3 fingers.
• Significance :
• Positive results: Easy insertion of a 3 cm deep flange of the
laryngoscope blade
• <3 cm: difficult laryngoscopy
• <2 cm: difficult LMA insertion
• Affected by TMJ and upper cervical spine mobility

24. Sternomental
distance
• Distance from the upper border of
the manubrium to the tip of
mentum, neck fully extended,
mouth closed
• Minimal acceptable value – 12.5
cm
• Single best predictor of difficult
laryngoscopy and intubation (Has
high sensitivity & specificity).

25. Test for assessing adequacy of the oropharynx for
laryngoscopy and intubation
•Mallampati grading (samsoon and
young‘s modification)
•Narrowness of the palate

26. Mallampati score
• Roughly corresponds to Cormack
and Lehane‘s laryngoscopy views
• Class I (easy)—visualization of the
soft palate, fauces, uvula, and both
anterior and posterior pillars
• Class II—visualization of the soft
palate, fauces, and uvula
• Class III—visualization of the soft
palate and the base of the uvula
• Class IV (difficult)—the soft palate
is not visible at all

27. Significance of mallampati score
• Class III or IV: signifies that the angle between the base
of tongue and laryngeal inlet is more acute and not
conducive for easy laryngoscopy
• Limitations
• Poor interobserver reliability
• Limited accuracy
• Good predictor in pregnancy, obesity, acromegaly

28. CORMACK - LEHANE
Grading at direct
laryngoscopy
• Grade 1: Full exposure of
glottis (anterior + posterior
commissure)
• Grade 2: Anterior
commissure not visualised
• Grade 3: Epiglottis only
• Grade 4: No glottic structure
visible.

30. How to predict difficult placement
of supraglottic devices (RODS)
• Restricted mouth opening
• Obstruction of the upper airway
• Distrupted upper airway as following trauma,burn,caustic ingestion .
• Stiff lung (poor lung or thoracic compliance)
• Suggested by Hung and Murphy (Canadian journal of anesthesia 2004:10:963-8)

31. How to predict difficulty in creating surgical airway
(BANG)
•Bleeding tendency
•Agitated patient
•Neck scarring
•Growth or vascular abnormality in region of
surgical airway.

36. Reflection
• Airway assessment is a critical part .
• The difficult airway assessment must be performed prior
to ALL attempts.
• While this criteria helps identify difficult airways, it does
not guarantee an easy intubation—Be Prepared!
• Nothing is more expensive than the missed opportunity