Airway

1. Preoperative Airway
Assessment
Dr KEERTHIRAM
MODERATOR
Dr PRAVEEN KUMAR

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

3. Why it is necessary ??
• 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 with
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. The purpose of undertaking airway assessment is
to diagnose the potential for difficult airway for:
1.Optimal patient preparation.
2.Proper selection of equipment and technique
3.Participation of personnel experienced in the
difficulty airway management

8. ESSENTIAL COMPONENTS OF AIRWAY
ASSESSMENTS
• History taking
• General examination of patients
• Specific tests/indices to predict difficult airway

9. Airway assessment
• History
• Previous h/o difficult airway
• Surgery/burns
• Concurrent disease
• General examination
– Patency of nares
• 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
• Specific tests
• Investigations
– Nasoendoscopy
– X-ray
– CT/MRI
– Flow volume loop

10. History taking
• Previous anesthesia records may reveal a
documented history of difficult airway
• History of previous surgeries,burns,trauma or
tumor in and around the oral cavity,neck,cervical
spine should be asked

11. Components of the Airway
Examination
 Nostril patency
 Length of the upper incisors
 Teeth:loose teeth,bucking,missing teeth,capped,cracked)
 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,Beard
 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
 Small mandible,retrognathia
 Facial deformity,trauma
 Scars (Burns,tracheostomy)

12. General, physical and
regional examination
1.Patency of nares : look for masses inside
nasal cavity(e.g. polyps) ,deviated nasal
septum, etc.
2. Mouth opening of at least 2 large finger
breadths
3.Teeth : Prominent upper incisors,Loose
teeth,Missing teeth

13. 4. Palate : A narrow, high arched palate may
present difficulty.
5. Assess patient’s ability to protrude the
lower jaw beyond the upper incisors.
6. Temporo-mandibular joint movement :
It can be in restricted ankylosis/fibrosis
tumors, etc.
7. Measurement of submental space
(hyomental/Thyromental length > 6 cm)

14. • 8. Observation of patient’s neck : A short,
thick neck
• 9. Presence of hoarse voice/stridor or
previous tracheostomy may suggest
stenosis
• 10. Infections of airway (e.g. epiglottitis,
abscess, croup,bronchitis, pneumonia).
• 11. Physiologic conditions : Pregnancy and
obesity

15. How do you assess ??
 The airway may be assessed for difficult airway using :-
-Individual indices
-Group indices(with and without scoring)
 Mask ventilation precedes laryngoscopy, which inturn
followed by, intubation.
So the assessment should be in a systemic manner.

16. Predictors of difficulty to face mask
ventilate (OBESE)
1.The Obese (body mass index > 26
kg/m2)
2.The Bearded
3.The Elderly (older than 55 y)
4.The Snorers
5.The Edentulous
(=BONES)

17. Predictors of difficulty to face mask
ventilate (MOANS)
• MOANS
This is identicle to BONES except ‘M’.
-Mask seal difficult due to receding mandible,syndromes
with facial abnormalities,burn stricture etc.
-Obesity, upper airway Obstruction
-Advanced age
-No teeth
-Snorer

18. Mask Seal
• Small Hands
• Wrong Mask Size
• Oddly Shaped Face
• Bushy Beard
• Facial Trauma
MOANS

19. Obesity or Obstruction
• Obesity
– Heavy chest
– Abdominal contents inhibit movement of
the diaphragm
– Increased supraglottic airway resistance
– Billowing cheeks
– Difficult mask seal
– Quicker desaturation
MOANS

20. Obesity or Obstruction
• 3rd
Trimester Pregnancy
– Increased body mass
– Quick desaturation
– Increased Mallampati Score
– Gravid uterus inhibits movement of the
diaphragm
MOANS

21. Age > 55
• Associated with BVM difficulty, possibly
due to loss of tone in the upper airway
MOANS

22. No Teeth
• Face tends to “cave in”
• Consider leaving dentures in for BVM
and remove for intubation
MOANS

23. Sniffing Position
Align oral, pharyngeal, and laryngeal axes to
bring epiglottis and vocal cords into view.

24. Difficult Ventilation:
Obese Patients
 Excess soft tissue causes obstruction
 Use both OP and NP airways
 Two hands for mask seal and jaw thrust
 Avoid pushing in on soft tissue under jaw
 may force into airway, worsen obstruction
 Place patient in reverse Trendelenburg
 decreases abdominal pressure on
diaphragm
 lowers amount of pressure needed to bag

25. 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 assesment
- Arne’s simplified score

26. 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.

27. Grade Reduction of A.O.Extension
1 none
2 One third
3 Two third
4 complete
Grades 3 and 4 : Difficult laryngoscopy
Grading of reduction in A.O.Extension
Grade I : > 35°
Grade II : 22-34°
Grade III : 12-21°
Grade IV : < 12°

28. • Flexion movement of the cervical spine can be
assessed by asking the patient to touch his
manubrium sternii with his chin. If done, the above
maneuver assures a neck flexion of 25- 35
degree. Flexion and the extension movement if
within the normal range ,three axis
( oral,pharyngeal & laryngeal axis) can be brought
into a straight line.

29. DELIKAN TEST
Place the index finger of each hand, one underneath
the chin and one under the inferior occipital
prominence with the head in neutral position. The
patient is asked to fully extend the head on neck. If the
finger under the chin is seen to be higher than the
other, there would appear to be no difficulty with
intubation. If level of both fingers remains same or the
chin finger remains lower than the other, increased
difficulty is predicted.

30. 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.

31. 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 5th
digit.
* Grade2 - Deficiency in the inter-phalangeal areas of
2nd to 5th
digit.
* Grade 3 - Only the tips of digits seen.

32. Palm Print as a Predictor of
Difficult Airway in DM

33. ASSESSMENT OF TMJ FUNCTION
1.Index finger is placed in front of the tragus & the patient is
asked to open his mouth as wide as possible.As the condyle
of the mandible slides forward,the index finger in front of the
tragus can be intented in its space.This suggests good sliding
function of mandible.
2.Ask the patient to open his mouth wide and place three
fingers(index,middle and ring) in the opening.if done, mouth
opening is >5cm and adequate for laryngoscopy

34. INTER-INCISOR GAP
• Inter-incisor distance with maximal mouth opening
• Normal value > 5 cm / admits 3 fingers.
Significance :
• Positive results: Easy insertion of the laryngoscope
blade
• < 3 cm: difficult laryngoscopy
• < 2 cm: difficult LMA insertion
Affected by TMJ pathology

35. Significance-
Class B and C: difficult laryngoscopy

36. 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.
• Furthermore,laryngoscopy pushes the
tongue into this space and if reduced
or narrow,exposureof the glottis may
be inadequate.

37. Thyromental Distance
Measure from upper edge of thyroid cartilage
to chin with the head fully extended.
Normal is >6.5 cm
If the thyromental distance is short, <3 finger
widths / < 6 cm, 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
PATIL’S TEST

38. Limitations
• 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
Thyromental Distance

39. HYO MENTAL DISTANCE
• Distance between mentum
and hyoid bone
• Grade I : > 6cm
• Grade II: 4 – 6cm
• Grade III : < 4cm (a/w
impossible laryngoscopy &
Intubation)

40. STERNOMENTAL DISTANCE
(SAVVA TEST)
• Distance from the upper border of the manubrium/sternal
notch 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).

41. UPPER LIP BITE /CATCH TEST
• Class I: Lower incisors can bite the upper lip above
vermilion line
• Class II: can bite the upper lip below vermilion line
• Class III: cannot bite the upper lip
Significance
• Assessment of mandibular movement and dental
architecture
• Patients having class III of upper lip bite test may be
expected to have Cormack and Lehane’s grade 3 and 4
laryngoscopic view of larynx.

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

43. Mallampati Score
• Performed with patient in a sitting
position, head neutral, mouth widely
open and tongue protruding out without
phonating
• May be unable to properly assess this in
an emergent field situation

44. Modified Mallampatti Score
Samsoon & Young's Modified Mallampati Classification is used to predict the ease of
endotracheal intubation.
Initially, the Mallampati scoring system (1985) had only 3 classes,modified by
Samsoon and Young to include class 4.
Later class 0 was also added(epiglottis is also visible)
Failure of mallampatti score is, it missed to include evaluation of two important factors
affecting visualization of glottis
1 Neck mobility
2 Size of mandibular space

46. SIGNIFICANCE OF MMP 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

47. Narrowness of the palate:
Evaluate the narrowness of the palate while
performing Mallampatti grading
A narrow,high arched palate offers very little
space for laryngoscopy and simultaneous
endotracheal intubation.

48. Assessment for quality of glottic
viewing during laryngoscopy
Indirect mirror laryngoscopic view
Direct laryngoscopy ‘awake look’
-cormack and lehane grading
Grading ease of intubation
POGO (percentage of glottic opening)
scoring

49. CORMACK - LEHANE
Grading at direct laryngoscopy
• Grade 1: Full exposure of glottis (anterior + posterior
commissure)
Grade 2: Anterior commissure not
visualised Grade3: Epiglottis
only
Grade 4: No glottic structure visible.
Grade I =  success & ease of intubation

51. Group indices
- Wilson’s score
- Benumof’s analysis
- Saghei & safavi test
- Lemon assesment
- Arne’s simplified score

52. Wilson’s risk score
Score
Weight 0=<90kg
1=>90kg
2=>110kg
Head and
neck
movement
0=Above 90degrees
1=About 90degrees
2=Below 90degrees
Jaw
movement
0=IG>5cm or SLux >0
1=IG<5cm and SLux = 0
2=IG<5cm and SLux<0
Receding
mandible
0=Normal
1=Moderate
2=Severe
Buck teeth 0=Normal
1=Moderate
2=Severe
• Head movement assessed with
pencil taped to a patient’s forehead.
•IG = Interincisor gap measured with
mouth fully open.
•SLux = Maximal forward protrusion
of the lower incisors beyond the
upper incisors.
•score 5 or < =easy
laryngoscopy
•Score 8-10 =severe difficulty
in laryngoscopy

53. BENUMOF’S 11 PARAMETER ANALYSIS
Parameter
1. Buck teeth
2. Subluxation
3. Interincisor gap
4. Upper incisor length
5. Palate configuration
6. Mallampati class
7. TM distance
8. Mandibular space
compliance
9. Neck length
10. Neck thickness
11. Head and neck movts
Minimum acceptable
value
No overriding
SLux > 0
>3cm
<1.5cm
No arching/narrowness
<2
>5cm / >3FB
Soft to palpate
>8cm
43cm
Normal ROM
4-2-2-3 rule
4 for tooth
2 for inside of mouth
2 for mandibular space
3 for neck examination.

54. SAGHEI & SAFAVI’S
• Weight
• Tongue protrusion
• Mouth opening
• Upper incisor length
• Mallampati class
• Head extension
Any 3 indices if present
>80kg
< 3.2cm
<5cm
>1.5cm
>1
<70 degree
Prolonged laryngoscopy

55. Arne’s simplified score model
• Risk factor simplified score
• Previous knowledge of difficult intubation
No 0
Yes 10
• Pathologies associated with difficult intubation
No 0
Yes 5
• Clinical symptoms of airway pathology
No 0
Yes 3
• Inter-incisor gap (IG) and mandible luxatum (ML)
IG > 5 cm or ML >0 0
IG 3.5-5cm and ML=0 3
IG<3.5 cm and ML<0 13

56. Arne’s simplified score contd.
• Thyromental distance simplified score
>6.5cm 0
< 6.5cm 4
• Maximum range of head & neck movement
Above 100° 0
About 90° (90° ± 10°) 2
Below 80° 5
• Mallampati’s modified test
Class 1 0
Class 2 2
Class 3 6
Class 4 8
Total...... 48
Score of >11 is predictive of difficult tracheal intubation

57. .

58. LOOK Externally
• Beards or facial hair
• Short, fat neck
• Morbidly obese patients
• Facial or neck trauma,Burns
• Broken teeth (can lacerate balloons)
• Receding jaw
• Dentures (should be removed)
• Prominent upper incisers/Buck teeth
• Macroglossia
• A narrow or abnormally shaped face
• High arched palate

59. E-Evaluate the 3-3-2 rule
59
3 fingers fit in mouth(Access to airway and
obtaining glottic view)
3 fingers fit from mentum to hyoid bone(To
assess the ability of mandible to accomodate the
tongue during laryngoscopy)
2 fingers fit from the floor of the mouth to the
top of the thyroid cartilage(To assess for high
larynx)

61. Upper & Lower Face
• Measure the size of the upper face as compared
to the lower face.
• Should be roughly the same.
• If the lower face is longer than the upper face then
you should anticipate some degree of difficulty
lining up the structures

62. Obstruction
• Laryngoscopy or intubation may be more
difficult in the presence of an obstruction
– Anatomy
– Trauma
– Foreign body obstruction
– Edema (burns)

63. 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
 Foreign body
 Other – Pregnant/full stomach

64. Neck Mobility
• Ideally the neck should be able to extend
back approximately 35°
• Problems:
– Cervical Spine Immobilization
– Ankylosing Spondylitis
– Rheumatoid Arthritis
– Halo fixation

65. 1. X-Ray neck (lateral view) :
• Occiput - C1 spinous process
distance< 5mm.
• Increase in posterior mandible
depth > 2.5cm.
• Ratio of effective mandibular
length to its posterior depth
<3.6.
• Tracheal compression.
RADIOGRAPHIC
PREDICTORS

66. • The posterior depth of the mandible
(PDM) i.e. the distance between the
bony alveolus immediately behind the
3rd molar tooth and the lower border of
the mandible is an important measure
in determining the ease or difficulty of
laryngoscopy.
• PDM expressed as a ratio of the
effective mandibular length (EML), is
another useful predictor. EML is the
distance between the tip of lower
incisors to the temporomandibular joint
(Fig 1.11). If the EML is less than 3.6
times the PDM, direct laryngoscopy will
be difficult.

67. 2. CT Scan:
• Tumors of floor of mouth, pharynx, larynx
• Cervical spine trauma, inflammation
• Mediastinal mass
• Flow volume loop
• MRI
• Flexible bronchoscope
ADVANCED INDICES

68. Rapid asessment of the airway
by rule of 1-2-3
• 1.Movement of TM joint-can insinuate one
finger near tragus with mouth fully open.
• 2.Extent of mouth opening-interincisor gap
atleast 2 fingerbreadths.
• 3.Size of mandibular space-thyromental
distance atleast three fingerbreadths.

69. To Summarize
• 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

70. CONCLUSION
No single airway asessement test has full
sensitivity or specificty. So all tests must
be combined and a comprehensive airway
assessment and prediction of the difficult
airway should be done.
Some patients however remain
undetected for difficult airway,so ALWAYS
BE PREPARED FOR DIFFICULTY…..

71. THANK YOU