2. Definition:
AIRWAY: The passage through which the air passes
during respiration.
DIFFICULT AIRWAY :According to ASA it is defied as
the clinical situation in which a conventionally trained
anesthesiologist is unable to maintain the oxygen
saturation above 90 % by using face-mask ventillation.
3. DIFFICULT MASK VENTILATION
According to ASA
‘The clinical situation in which a conventionally trained
anaestthesiologist experiences difficulty with mask
ventilation, difficulty with tracheal intubation or both’
4. Difficult Mask Ventilation: OBESE
O: Obesity i.e. BMI>26 kg/m
B: Beard
E: Edentulous
S: Snorer
E: Elderly
And also Difficult in maintain mask seal due to any
anatomical, congenital or acquired factors.
5. Anatomy:
PARTS OF AIRWAY
Upper Airway:
a. Mouth- opening of mouth to anterior tonsil or pillar.
b. Nostrils- adult nose= anterior posterior diameter 1.5-2 cm
,transverse diameter 0.5-1cm
c. Nasal Cavity-from nares to the end of the turbinates.
d. Nasopharynx- extends from posterior end of turbinates to the
posterior pharyngeal wall above the soft palate and consists of
the nasal cavity , septum, turbinates and adenoids.
6. Oropharynx-extends from soft palate above to
epiglottis below and anteriorly from anterior
tonsillar pillar to posterior pharyngeal wall , it
includes tonsil , uvula and the epiglottis.
Pharynx- extends from the base of skull to lower
border of cricoid cartilage
7. Larynx- extends form laryngeal inlet i.e C3-C4 to lower
border of cricoid cartilage (C5-C6)-[ Importance :
Phonation and Swallowing ] Contents : Unpaired
Cartilage = Thyroid , Cricoid and Epiglottis , Paired =
Arytenoid , Cornicuate and Cuneiform (most
vulnarable area for obstruction and trauma during
laryngoscopy)
8. 2. Lower Airway :
a. Trachea : extends from lower border of cricoid C6
to its division into the two main bronchi i.e till T4 it is
11-13 cm long .(Importance : Endotracheal tube lodges
in the mid trachea)
b. Bronchi and Bronchioles : Made up of
fibrocartilage and has secretory bronchial gland cells.
9. • 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.
10. • 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
16. 1) History:
Should be conducted when ever its feasible i.e. before
the initiation of anaesthetic care and airway
management inorder to:
- Detect any medical, surgical and anaesthetic factors.
- Examination of previous medical records if available.
17. 2) General, Physical and regional
Examination:
a. Patency of nares
b. Mouth Opening -2 large finger breadths
between upper and lower incisors in adults.
c. Teeth: Look for Prominent upper Incisors, Canines
with or without over bitiong or edentulous state.
18. (a) Shows mandibular advancement beyond the upper teeth.
(b) Shows that the mandible cannot be advanced beyond the upper teeth. (c) Shows
that the lower incisors cannot reach the upper teeth.
• d. Palate
• e. Patients ability to protrude the lower jaw beyond
the upper incisors.
19. f. Temporo-mandibular joint movement: restricted in
ankylosis, tumors, fibrosis etc
g. Measurement of Submental Space: atleast >6cm
h. Patient’s Neck: For Sniffing Position i.e. ideal
position for intubation. Look for:
Short Neck,
Thick neck
Mass present in the neck
Extension of neck
Mobility of neck
20. i. Presence of Stridor/Hoarse voice or previous
Tracheostomy may suggest Stenosis
j. Systemic or Congenital Diseases
k. Infection of Airway
l. Physiologic Conditions: Pregnancy or Obesity
21. 3. Specific tests for Assessment
A. Anatomical Criteria
1. Relative Tongue and Pharyngeal Size:
Mallampatti Test: In 1983 Mallampatti SR
gave a hypothesis i.e. clinical signs to predict difficult
tracheal intubation. Which included only 3 Class.
22. Original Mallampati Scoring:
Class 1: Faucial pillars, soft palate and uvula could be
visualized.
Class 2: Faucial pillars and soft palate could be
visualized, but uvula was masked by the base of the
tongue.
Class 3: Only soft palate visualized.
24. Class 1- Visualization of the Soft palate, faucial
pillars, uvula and hard palate
Class 2- Soft palate, fauces, uvula and hard palate
Class 3- Soft palate, base of uvula and hard palate
Class 4- only Hard palate
Note: To avoid false positive or false negative, this test
should be repeated twice
25. Grade 0: By Ezri et al. proposed the addition of a new
airway class 0 (epiglottis seen on mouth opening and
tongue protrusion)
26. Atlanto Occipital Joint Extension: to assess Sniffing
or Magill Position for intubation i.e. alignment of oral,
pharyngeal and laryngeal axes. Patient is asked to
hold neck erect, facing directly to the front and then
he is asked to extend the head maximally and then the
examiner estimates the angle transversed by the
occlusal surface or can use Goniometer to assess more
accurately.
27.
28. Grading of Extension:
Grade 1- >35 degrees
Grade 2- 22 to 34 degrees
Grade 3- 12 to 21 degrees
Grade 4- <12 degrees
29. 3- Mandibular Space
A. Thyromental Distance (T-M) aka Patil’s Test:
Distance from Mentum to Thyroid notch when
patient’s neck is fully extended.
<3 finger (Patients) breadth or <6 cm in adults-
Difficult
6-6.5cm- less difficult
>6.5cm- Normal
30. B. Mandibular-Hyoid Distance: Distance from Chin to
hyoid. Atleast Should be of 4 cm or 3 finger breadth. If
the distance is more then laryngoscopy becomes more
difficult
C. Sterno-mental Distance: Distance from Sternal
notch to the mentum. Measured when head is fully
extended with mouth closed. If less than 12 cm, it
indicated difficult intubation.
31. C. Inter-incisor distance:
Distance between upper and
lower incisors.
Normal- 4.6cms
Difficult- >3.8 cm
32. 4. Temporomandibular Joint :
1.The middle finger of each hand posterior and inferior
to the patient’s earlobes, place your index fingers just
anterior to the tragus and instruct the patient to open
widely Two distinct movements should be felt:
the first is rotational,
& the second involves advancement of the
condyler head .
Listen and palpate for clicks and crepitus, both of
which indicate joint dysfunction.
2.TMJ function may also be assessed by asking the
patient to insert two or three fingers (of their own
hand) held vertically, into the oral cavity in the
midline.
33. Normal adults are capable of inserting at least three
fingers, which corresponds to a range of mandibular
opening between 40 and 60 mm.
If the maximal mandibular opening is less than 30
mm in the adult, significant TMJ dysfunction is
present.
If less than 25 mm, it is unlikely that the larynx will
be visible using conventional laryngoscopy
If 20 mm or less, Keep alternate method ready
34. Different Scoring System:
Scoring System By Wilson and Colleagues:
They analyzed 5 parameters i.e. weight, head and neck
movement, jaw movement, Sliding mandibular,
receding mandible and buck teeth.
35. Parameters 0 1 2
Weight <90 90-100 >110
Head & Neck
Movement
>90 =90 degrees < 90 degrees
Jaw Movement > 5 cm =5 cm < 5 cm
Sliding mandible
beyond incisors
> 0 = 0 < 0
Receding
mandible
None Moderate Severe
Buck Teeth None Moderate Severe
Patient scoring 5 or< =Easy Laryngoscopy
6-7= Moderate
8-10= Severe difficulty
36. -LEMON Airway Assessment Method:
L= Look externally i.e. facial trauma, large incisors,
beard, moustache etc
E= Evaluate 3-3-2 rule i.e. incisors distance- 3
fingers, Hyoid-mental-3 finger and thyroid-mouth- 2
finger
M= Mallampatti
O= Obstruction like tonsil, trauma, peritonsillar
abscess
N= Neck Mobility
37. 1 = Inter-incisor distance
in fingers, 2 = Hyoid mental distance in fingers, 3 = Thyroid to floor
of mouth in fingers
38. Magboul’s 4 M & Ms with (STOP) For assessing
Difficult Airway:
M= Mallampatti
M= Measurement
M= Movement
M=Malformation and STOP
S= Skull i.e. hydro or microcephalus
T= Teeth
O= Obstruction due to obesity, short neck, long neck,
swelling in and around oral cavity
P= Pathology i.e. Pierre Robinson Syndrome, Downs
Syndrome etc
39. If a patient score 8 or more than 8, he/she is likely to
be a difficult intubation.Score 1 2 3 4
Mallampatti Grade 1 Grade 2 Grade 3 Grade 4
Measurement 3 Mouth
Opening
2 Thyromental 2 Hypo mental 1 Subluxation
Movement Left Right Flexion Extension
Malformation Skull Hydro/
Microcephalus
Teeth/Buck
teeth &
Macro/Micro
Jaw
Obstruction
Obesity
Short/Bull
neck &
Swelling
Pathology &
Syndrome:
-Pierre-
Robinson
-Treacher-
Colins
-Quinsy
-Downs
TOTAL 4 4 4 4
40. -Benumof’s 11 parameter
Analysis:
Parameter Minimum acceptable value
Weight <1.5 cm
Buck teeth Absent
Subluxation Yes
Interincisor gap >3 cm
Palate Configuration No arching/Narrowness
Mallampatti <2 cm
TM Distance >5 cm
SMS Compliance Soft to palpate
Neck thickness Qualitative (>33 cm)
Length of neck >8 cm
Head & Neck Movement Normal Range
43. B. Direct Laryngoscopy and Fiberoptic
Bronchoscopy:
4 grades of direct under laryngoscopic view by Cormack
and Lehane (1984)
Grade I – Visualization of entire laryngeal aperture.
Grade II – Visualization of only posterior
commissure of laryngeal aperture.
Grade III – Visualization of only epiglottis.
Grade IV – Visualization of just the soft palate.
Grade III and IV predict difficult intubation
44.
45. 5- Radiographic Assessment
1. From Skeletal Films
a. Mandibular-Hyoid distance
b. Atlanto-occipital gap.
c. Relation of mandibular angle and hyoid bone with
cervical vertebrae and laryngoscopy grading
d. Anterior/posterior depth of mandible
e. C1-C2 gap
1 = Effective mandibular length, 2 =Posterior
mandibular depth, 3 = Anterior mandibular
depth, 4 = Atlanto-occipital gap, 5 = C1 – C2
gap.
46. 2. Fluoroscopy for chords mobility and airway malacia.
3. Oesophagogram
4. USG
5. CT-Scan/MRI
6. Video optical intubation stylets.
47. 6. Predictors of difficult airway in diabetics:
a. Palm Sign: The patient is made to sit; palm
and fingers of right hand are painted with blue ink,
patient then presses the hand firmly against a white
paper placed on a hard surface. It is categorized as:
Grade 0 – All the phalangeal areas are visible.
Grade 1 – Deficiency in the interphalangeal areas
of the 4th and 5th digits.
Grade 2 – Deficiency in interphalangeal areas of
2nd to 5th digits.
Grade 3 – Only the tips of digits are seen.
49. Prayer Sign:
Patient is asked to bring both the palms together as
‘Namaste’ and sign is categorized as–
Positive – When there is gap between palms.
Negative – When there is no gap between palms.
50.
51. Summary of all the Tests:
Six standards in the evaluation of airway
a. Temporomandibular mobility – One finger
b. Inspection of mouth, oropharynx – Mallampati
classification – Two fingers
c. Measurement of mento-hyoid distance (4 cm) in
adult
– Three fingers.
52. d. Measurement of distance from chin to thyroid
notch – (5 to 6 cm) – Four fingers
f. Ability to flex head towards chest, extend head at
atlanto-occipital junction and rotate head, turn
right and left (five movements).
g. Symmetry of nose and patency of nasal passage.
53. Assessment of pediatric airway:
Physical examination : It should focus on the
anomalies of face, head, neck and spine.
Evaluate size and shape of head, gross features of the
face; size and symmetry of the mandible, presence of
sub-mandibular pathology, size of tongue, shape of
palate, prominence of upper incisors, range of motion
of jaw, head and neck.
54. The presence of retractions
(suprasternal/sternal/infrasternal/ intercostal) should
be sought for they usually are signs of airway
obstruction.
Breath sounds – Crowing on inspiration is indicative of
extrathoracic airway obstruction whereas, noise on
exhalation is usually due to intrathoracic lesions.
55. Noise on inspiration and expiration usually is due to a
lesion at thoracic inlet.
Obtaining blood gas and O2 saturation is important to
determine patient’s ability to compensate for airway
problems.
Transcutaneous CO2 determinations are very helpful
in infants and young children.
56. Recent Advances:
Ultrasound of the airway:
to visualise anatomical structures in supraglottic,
glottic and subglottic region.
> 28 mm thickness of the pretracheal soft tissue & neck
circumference > 50 cm indicate difficult intubation.
57. Conclusions:
The importance of taking the time to conduct a thorough
evaluation of the airway.
That there is no single guaranteed test available to predict
the problem airway.
We need to ask ourselves a more fundamental question
when dealing with airway issues. “Will I be able to
oxygenate and ventilate this patient if or when he/she
becomes unconscious?”
We should be able to answer that question affirmatively in
all cases, and
if not, we need contingency plans.
58. Reference:
Miller’s Anaesthesia 7th Edition
Airway Management By Rashid Khan 4th Edition
Indian Journal Of Anaesthesia, August 2005;49(4):257-
262
Indian Journal Of Anaesthesia, Sep 2011;55(5):456-457
