1. Seminar Difficult Airway: Assessment and Management Algorithms
Presenter : Anil Agarwal
Date : March 19, 2007

2. Difficult Airway: Definitions
A clinical situation in which a conventionally trained anaesthesiologist experiences difficulty with mask ventilation, difficulty with tracheal intubation or both
Difficult airway: spectrum
Difficult : spontaneous/mask ventilation
laryngoscopy
tracheal intubation
Ref. Anesthesiology, May 2003

3. Definitions (Contd.)
Difficult mask ventilation: A clinical situation when either,
It is not possible for unassisted anaesthesiologist to maintain the SpO2 > 90% using 100% O2 and positive pressure mask ventilation in a patient whose SpO2 was > 90% before the anaesthetic intervention or
It is not possible for the unassisted anaesthesiologist to prevent or reverse signs of inadequate ventilation during mask ventilation

4. Definitions (Contd.) Difficult laryngoscopy
It is not possibe to see any portion of the vocal cords after multiple attempts at conventional laryngoscopy (3, ASA)
Difficult tracheal intubation
A clinical situation in which intubation requires more than three attempts or ten minutes using conventional laryngoscopic techniques

5. Definitions (Contd.)
Optimal attempt at laryngoscopy – can be defined as
Performance by a reasonably experienced laryngoscopist
The use of the optimal sniffing position
The use of OELM
One change in length/type of blade

8. Assessment of Difficult Airway
History
General physical examination
Specific tests for assessment
Difficult mask ventilation
Difficult laryngoscopy
Difficult surgical airway access
Radiologic assessment

9. History
Congenital airway difficulties: e.g. Pierre Robin, Klippel-Feil, Down’s syndromes
Acquired
Rheumatoid arthritis, Acromegaly, Benign and malignant tumors of tongue, larynx etc.
Iatrogenic
Oral/pharyngeal radiotherapy, Laryngeal/tracheal surgery, TMJ surgery
Reported previous anaesthetic problems
Dental damage, Emergency tracheostomy, Med-alerts, databases, previous records

10. General Examination
Adverse anatomical features: e.g. small mouth, receding chin, high arched palate, large tongue, morbid obesity
Mechanical limitation: reduced mouth opening, post-radiotherapy fibrosis, poor cervical spine movement
Poor dentition: Prominent/loose teeth
Orthopaedic/neurosurgical/orthodontic equipment
Patency of the nasal passage

11. Specific Tests Basic categories
Evaluation of tongue size relative to pharynx
Mandibular space
Mobility of the joints
TMJ
Neck mobility

12. Inter-incisor Gap Inter-incisor distance with maximal mouth opening
Minimum acceptable value > 4 cm
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

13. Mandibular Protrusion Test
Class A: able to protrude the lower incisors anterior to the upper incisors
Class B: lower incisors just reach the margin of upper incisors
Class C: lower incisors cannot reach the margin of upper incisors
Significance
Class B and C: difficult laryngoscopy

16. Upper Lip Bite 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: can not bite the upper lip
Significance
Assessment of mandibular movement and dental architecture
Less inter observer variability
Ref. Anesthesia & Analgesia, 2003

17. Mallampati Test Patient in sitting position
Maximal mouth opening in neutral position
Maximal tongue protrusion without arching
No phonation
Class I: faucial pillars, soft palate, uvula visible
Class II: faucial pillars, soft palate visible
Class III: only soft palate visible
Somsoon-Young’s modification
Class IV: soft palate not visible

18. 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
Anesthesia & Analgesia, February 2006

19. Correlation between MMP score and laryngoscopy grade
MMP class
Cormack and Lehane grade
Grade 1
Grade 2
Grade 3
Grade 4
Class I (73%)
59%
14% -
Class II (19%)
5.7%
6.7%
4.7%
1.9%
Class III & IV (8%)
0.5% 5%
2.5%
Airway Management, Jonathan Benumof

20. Class Zero Mallampati
Visualisation of any part of epiglottis during MMP test
Associated with easy laryngoscopy
Ref. Ezri et al, Anesthesia and Analgesia, 2001
Contrasting View
Class zero MMP: difficult airway possible  large epiglottis hinder laryngoscopic view as well as ventilation
Ref. V. Grover, Canadian Journ Anesth, 2005

21. Evaluation of Mandibular Space
Thyromental distance (Patil test)
Distance from the tip of thyroid cartilage to the tip of mandible
Neck fully extended
Minimal acceptable value – 6.5 cm
Significance
Negative result – the larynx is reasonably anterior to the base of tongue

22. Thyromental Distance 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 < 25 or 23.5 – very sensitive predictor of difficult laryngoscopy
Anesthesiology, May 2005

23. Sternomental Distance (Savva Test)
Distance from the upper border of the manubrium to the tip of mandible, neck fully extended, mouth closed
Minimal acceptable value – 12.5 cm

24. Evaluation of Neck Mobility
Clinical methods
Patient is asked to hold the head erect, facing directly to the front  maximal head extension  angle traversed by the occlusal surface of upper teeth
Grade I : > 35°
Grade II : 22-34°
Grade III : 12-21°
Grade IV : < 12°

25. Neck Mobility: Clinical Assessment
Flexing the head on the neck  immobilize the lower cervical spine  full head extension  angle traversed by the vertex or forehead
Significance
Angle > 90°
Specific test for atlanto-occipital joint extension

26. Neck mobility (contd.)
Placing one finger on the patient’s chin  One finger on the occipital protuberance
Result
Finger on chin higher than one on occiput  normal cervical spine mobility
Level fingers  moderate limitation
Finger on the chin lower than the second  severe limitation

27. Combination of Predictors
Wilson Score
5 factors
Weight, upper cervical spine mobility, jaw movement, receding mandible, buck teeth
Each factor: score 0-2
Total score > 2  predicts 75% of difficult intubations

28. “LEMON” Assessment L - Look externally (facial trauma, large incisors,
beard, large tongue)
E - Evaluate rule
inter incisor gap
hyomental distance
2 - hyoid to thyroid distance
M - MMP score
O - Obstruction (epiglottitis, quinsy)
N - Neck mobility
Ron and Walls’ Emergency Airway Management

29. Cormack-Lehane Grading of Laryngoscopy
Grade 1: Full exposure of glottis (anterior + posterior commissure)
Grade 2: Anterior commissure not visualised
Grade 3: epiglottis only
Grade 4: Visualization of only soft palate

30. Cook’s Modification of Laryngoscopy Grade
Cormack-Lehane grade 2 & 3
2a : Posterior part of glottis visible
2b : Only arytenoids visible
3a : Epiglottis visible, can be lifted
3b : Epiglottis visible, but fixed
Easy: Grade 1 and 2a
Restricted: Grade 2b and 3a
Difficult: Grade 3b and 4
Ref. Cook et al, Anaesthesia, 1999

31. Predictors of Difficult Mask Ventilation
Age > 55 years
BMI > 26 kg/m2
History of snoring
Beard
Edentulous
Langeron et al, Anesthesiology, November 2006

32. Predictors of Problems with Back-Up Techniques
LMA Insertion
Mouth opening < 2 cm
Intraoral/pharyngeal masses (e.g. lingual tonsils)
Direct Tracheal Access
Gross obesity
Goitre
Deviated trachea
Previous radiotherapy
Surgical collar

33. Specific Tests for Assessment: Statistical significance
Predicted difficult airway
Truly difficult airway
Yes No TP FP FN TN

34. Statistical significance (Contd.)
Sensitivity = TP / TP + FN
Specificity = TN/TN+FP
Positive predictive value = TP/TP+FP
Negative predictive value = TN/TN+FN

35. Statistical Significance of Bedside Predictors
Diagnostic test
Sensitivity
Specificity
MMP class
49%
86%
TMD
20%
94%
Sternomental distance
62%
82%
Mouth opening
22%
97%
Wilson risk score
46%
89%
MMP + TMD
56%

36. Radiographic Predictors
X-Ray neck (lateral view) :
Atlanto-occipital gap
C1-C2 gap
Posterior depth of mandible- distance between the bony alveolar margin just behind 3rd molar tooth and lower border of mandible.
Tracheal compression

38. Radiologic Predictors
CT Scan:
Tumors of floor of mouth, pharynx, larynx
Cervical spine trauma, inflammation
Mediastinal mass
Helical CT (3D-reconstruction):
Exact location and degree of airway compression

39. Difficult airway : specific subgroups
Pediatrics
Obstetrics
Obesity
Systemic diseases with airway implications, e.g. rheumatoid arthritis, diabetes, ankylosing spondylitis.

40. Pediatric difficult airway
History:
Past difficult intubation
Airway problems associated with feeding
Syndromes related to pediatric difficult airway
Stridor

42. Pediatric difficult airway
Mouth opening
Size of tongue
Palate- narrow, high arched, cleft
Schwartz-hyoid maneuver –
A-P distance from middle of inside of mentum to hyoid measured: >1.5cm. (neonates), >3cm.(children).
Frederic Berry’s Anesthesia for difficult pediatric patients

43. Difficult obstetric airway: predictors
MMP Class 3 or 4
Edema of tongue, supraglottic and glottic areas; (history of rapid weight gain,pre-clampsia, change in voice)
Large breasts, full dentition
Mucosal congestion of nose, pharynx,etc.

44. Difficult airway :obesity
Difficult spontaneous ventilation in obstructive sleep apnea
BMI >26 – predicts difficult mask ventilation
Difficult intubation predictors-
MMP Score >3
Neck circumference > 16 inches

45. Systemic Diseases : Airway Ramifications
Rheumatoid Arthritis:
TMJ arthritis ( inter incisor gap, MMP score )
Cricoarytenoid arthritis (dysarthria, stridor,hoarseness )
Cervical spine mobility – ankylosis, atlanto-axial instability.

47. Diabetes mellitus: stiff joint syndrome
Palm print :
Patient’s fingers and palms painted with blue ink and pressed firmly against a white paper
Grade 1- all phalangeal areas visible
Grade 2- deficient interphalangeal areas of 4th and 5th digits
Grade 3- deficient interphalangeal areas of 2nd to 5th digits
Grade 4- only tips seen.
Prayer sign.

48. Difficult airway: neurosurgical perspective
Diseases of the cervical spine
Trauma
Pituitary disease, e.g. acromegaly
Ref. Dr. Umamaheswara Rao, Indian J. Anaesth. 2005

49. Diseases of the Cervical Spine
Limited neck mobility
Congenital  Klippel-Feil syndrome
Acquired
Rheumatoid arthritis
Ankylosing spondylitis
Cervical spine instability
Congenital
Down’s syndrome
CVJ anomalies
Mucopolysaccharidosis
Trauma

50. Klippel-Feil Syndrome
Clinical triad
Cervical vertebral fusion
Short neck
Low-set hairline
Increase likelihood of airway obstruction
Cause: associated anomalies e.g.
CNS
Cervicomedulary junction involvement
Arnold-chiari malformation
Ref. Airway Management by Jonathan Benumof

51. Down’s Syndrome Atlanto-axial instability Macroglossia Sleep apnea
Associated multisystem anomalies
Subglottic stenosis
Hypotonia

52. CVJ Anomalies
Affect the skeleton and neuraxis at the junction of cranium and cervical spine
Clinical manifestations
Short neck
Pain and stiffness of neck
Transient attacks of vertigo/unconsciousness
Limb weakness
Respiratory abnormalities
Ref. Journal of Neurosurgical Anesthesiology, 2006

53. Assessment: Chronic Diseases of Cervical Spine
History
Trauma
Weakness/numbness of hands
Preferred pillow height and sleeping position
Clinical examination
Neck posture
Neck mobility
Unstable cervical spine
Inspection and palpation of the midline alignment of the hyoid, thyroid and spinous processes
Loss of normal cervical lordosis

54. Cervical Spine Trauma: Assessment
Incidence in blunt trauma: 0.9 – 3%
History
Clinical examination
Radiologic assessment
NEXUS Criteria
Low risk trauma patient
No midline cervical tenderness
No focal neurologic deficit
Alert
No intoxication
No painful, distracting injury
Ref. Hoffman et al, NEJM, 2000

55. Radiologic Assessment
Suspicion of CSI
3-view cervical spine X-rays
Lateral
A-P
Open-mouth odontoid views
Cervical spine CT scan
Findings
Fracture spine
Marked prevertebral edema
Malalignment
Ref.: Harris et al, Spine, 2006

56. Radiologic Assessment (Cond.)
MRI
Best technique to ascertain the integrity of cervical soft tissues for potential instability
Recommended in patients with prolonged (> 72 hrs) depressed mental status
However, MR imaging is not superior to multidetector row CT scan in detecting unstable cervical spine injuries in obtunded patients with blunt trauma
Ref.: G. Hogan et al, Radiology, 2005

57. Acromegaly: Airway Implications
Macroglossia, thickened pharyngeal and laryngeal soft tissues, obstructive sleep apnea
Grades of airway involvement
Grade 1: No involvement
Grade 2: Nasal and pharyngeal mucosa hypertrophy
Grade 3: Glottic involvement e.g. glottic stenosis/ vocal cord paresis
Grade 4: Grade (2+3)
Ref. British Journal of Anaesthesia, 2000

58. Australian Incident Monitoring Study (AIMS)
Most useful aid- GEB, introducer
3 most common contributing factors
Obesity
Limited neck mobility
Limited mouth opening
Most common complications
Desaturation
Esophageal intubation
Inadequate preoperative assessment was the most common remediable cause

59. Guidelines vs Protocols
Guidelines- good clinical practice general recommendations deriving from a systematic analysis of available literature,
resources that allow for individual interpretation.
Protocols- based on definitive clinical evidence that mandates adherence to specific recommendations.

60. ASA task force on management of DA (Anesthesiology May 03;98)
Explicit descriptions of DA
Difficult face mask ventilation
Difficult laryngoscopy
Difficult tracheal intubation
Failed intubation
Purpose- facilitate mx. of DA, ↓adverse outcomes
Focus on anaesthesia care
All locations, all ages

61. ASA task force on management of DA
Basic preparation
Inform
Ascertain help
Preoxygenation
Supplemental oxygenation throughout
Portable storage unit
Rigid laryngoscope blades
ETTs
ETT guides
LMAs
FFOI equips RI
Em NI a/w vent
Em invasive a/w
Exhaled CO2 detector

62. ASA task force on management of DA
Strategy depending on
Anticipated surgery
Patient condition
Skill & preference of anaesthesiologist
4 basic problems
3 basic management choices
Primary approach
Alternative approach
Exhaled CO2 to confirm tracheal intubation

64. LMA in ASA DA algorithm

65. ASA task force on management of DA
Strategy for extubation of DA
Awake?
Adverse impacts on ventilation
Further A/w management plan
Guide for reintubation
Follow up

66. Limitations of ASA guidelines
Open ended, wide choice of techniques
Emphasis on prediction of difficult airway
No stratification of available a/w devices
No expression of strength of recommendation

67. DAS guidelines (Anaesthesia.2004.59)
Management of un-anticipated difficult intubation in an adult non-obstetric patient
Paediatric, obstetric patients & patients with upper a/w obstruction excluded
Flow charts based on series of plans
Careful planning with backup plans
Maintenance of oxygenation takes priority
Seek the best assistance available

71. SIAARTI guidelines (Minerva Anesthesiol 2005;71:617-57)
Doesn’t apply to paediatric patients
Defines strength of expressed recommendation
Defines difficult a/w control, ventilation, intubation & laryngoscopy
Difficulty prediction (severe/borderline)
Devices managament
Mandatory
Other devices, available upon request
Other mentions

72. SIAARTI guidelines (Planning in unpredicted difficult a/w)
Correct position
Alternative options (blade/stylet/introducer/ magill’s)
Oxygenation is mandatory
Urgency/ emergency of procedure
Elective sx
Deferrable urgent sx
Emergent sx

73. SIAARTI guidelines (Planning in unpredicted difficult a/w)
Immediate withdrawal in CL – IIIe & IV
Preliminary knowledge of alternative devices, training in FOI
Blind intubation via extraglottic devices not recommended in emergency/ after repeated attempts
Use of fiberscope in emergency situations is not recommended

74. SIAARTI guidelines (Planning in predicted difficult a/w)
Strategy depends upon
Surgery deferrability
Risk of vomiting
Skill of anaesthesist
Available instrumentation
Patient cooperation
Grade of predicted difficulty

75. SIAARTI guidelines (Planning in predicted difficult a/w)
Predicted severe DA
Maintain consciousness, spont. Breathing
1st choice – awake FOI
Surgery under RA not recommended
Intubation under direct vision
Retrograde intubation as an alternative to FOI

76. SIAARTI guidelines (Planning in predicted difficult a/w)
Predicted severe DA
Anaesthesia can be induced
Preoxygenation & ventilability evaluation
Laryngoscopy grading influences further choice
CVCI
1st choice- cricothyrotomy
Surgeons intervention as an exception

77. DA in paediatric patients (SIAARTI guidelines, Minerva Anesthesiol 2006;72:723-48)
Important anatomic & physiologic differences
Lack of cooperation
Intuabtion using sedoanalgesia/ GA+ topical LA
Preoxygenation mandatory
Maintain spontaneous breathing, check FM ventilability

78. DA in paediatric patients (SIAARTI guidelines)
Strategy depending on laryngoscopy view
Post comm→ change blade/stylet/introducer
Epiglottis only → introducer
Limited view of epiglottis → FOI
No laryngeal structure → FOI
Blind intubation not recommended
CVCI
Early use of LMA/EGA
Crocothyrotomy, TTJV

79. Failed intubation in obstetrics
Incidence- 1 in 300 to 1 in 750
Original description by Tunstall
(Anaesthesia 1976;31:850)
DAS guidelines may readily be extrapolated to pregnant patients
Editorial, Int J Obs Anesth Jan2007;16

80. Failed intubation in obstetrics (IJOA Jan2007;16:173)

81. Airway management in trauma
Challenges

82. Airway management in trauma
Scientific evidence
RSI
MILS
Tracheal tube introducer for routine use
Selection of laryngoscope blades (Mac/McCoy)
LMA as a temporary adjunct
(Emerg Med J 2006;23:3-11)

83. Airway management in trauma
RSI involves 4 experienced personnel
AMPLE history (ATLS course manual 1997)
Allergies
Medication
Past medical history
time of Last meal
Events leading to
OET is the technique of choice
No definition of safe cx spine ovement
Equipment option depend on operator experience & skill

84. Airway management in trauma (Emerg Med J 2006;23:3-11)

85. Cervical Spine Injury: Management Options
Manual in-line stabilization
Airway interventions requiring less neck movement
Jaw-thrust (ventilation)
Adjunctive device  ILMA, combitube
Cricothyrotomy
Least movement (0.1 mm) with fibre optic nasal intubation
Ref.: Brimacombe et al. Anesth Analg 2000

86. Influence of laryngoscope blade
No difference between Macintosh and Miller blades
McCoy laryngoscope
Angulated tip
Improves visualisation with less force, in neutral position
Ref.: Anaesthesia, 1999
Bullard laryngoscope
Rigid fibreoptic laryngoscope
Alignment of axes not required
Ref.: Hastings et al. Anesthsiology, 1995

87. Management Options (Contd.)
Flexible fibre optic bronchoscopy
Advantages
Minimal cervical movement required
Ability to perform post intubation neurologic assessment
Most appropriate technique for intubation in patients with CSI  still debated
No clinical outcome data to suggest better neurologic outcome with any single technique
Ref.: Crosby et al, Anesthesiology, 2006)

88. Airway Management: Acromegaly
Large face-masks, long-bladed laryngoscopes
Grade 3 or 4
Fibreoptic intubation
Tracheostomy
Ref. British Journ Anaesth, 2000
Secondary intubation techniques
Intubating LMA
Ref.: J Neurosurg Anesthesiol, 2004
Gum-elastic bougie
Ref. J Neurosurg Anesthesiol, 2006

89. Tracheal Extubation in the Difficult Airway
Risk factors: Difficult reintubation
History of previous difficult intubation
Airway edema due to surgical manipulation or volume resuscitation
Morbid obesity
Burns or smoke inhalation
Immobilized/unstable cervical spine
Ref.: A. Rudra et al. Indian J Anaesth, 2006

90. Difficult Airway: Extubation Strategies
ASA Recommendations
Relative merits of awake extubation versus extubation before return of consciousness
Evaluation of factors that may impair ventilation after extubation
Formulation of airway management plan if there is inadequate ventilation after extubation
Ref.: ASA Practice Guidelines, Anesthesiology, 2003

91. Extubation strategies
Cuff leak test
Performed in a spontaneously ventilating patient at risk of obstruction after extubation
Circuit disconnected  occlusion of ETT end and deflation of cuff  ability to breath around the ETT
Ref.: Fisher et al, Anaesthesia, 1992

92. Extubation Strategies
Conventional awake extubation
Extubation in a deep plane of anaesthesia followed by placement of LMA to decrease the risk of laryngospasm
Ref.: Brimacombe et al, Anaesthesiology, 1996
Extubation over a fibreoptic bronchoscope
Ref.: Cooper et al, Anesth Clin North America, 1995
Endotracheal ventilation and exchange catheters e.g.
Cook’s airway exchange catheter
Tracheal tube exchanger
Ref.: A. Rudra et al, IJA, 2006

93. Thank You