The ‘Difficult’ AirwayThe ‘Difficult’ Airway
Barbara Stanley FRCABarbara Stanley FRCA
ObjectivesObjectives Define “difficult”Define “difficult” Factors associatedFactors associated Airway tests – pro’s and con’sAirway tests – pro’s and con’s PlanPlan
Some DescriptionsSome Descriptions ‘‘difficult airway’difficult airway’ Mask ventilation vs Mask ventilation vs
laryngoscopy vs bothlaryngoscopy vs both ‘‘difficult difficult
laryngoscopy’ = laryngoscopy’ = Cormack and Lehane Cormack and Lehane grade 3 or 4grade 3 or 4
‘‘difficult intubation’ difficult intubation’ = more than 3 = more than 3 attempts or >10 minsattempts or >10 mins
Importance Importance PredictablePredictable Serious Serious
consequences for consequences for patientpatient
Planning and Planning and preparationpreparation
Alternatives Alternatives What to do if it all What to do if it all
goes horribly wronggoes horribly wrong
The Size of the ProblemThe Size of the Problem Incidence variably quoted at 1-8% Incidence variably quoted at 1-8% 11 Unanticipated quoted up to 18% Unanticipated quoted up to 18% 11 Failure to ventilate as well as intubate occurs Failure to ventilate as well as intubate occurs
in 15% difficult intubations in 15% difficult intubations 33 Abandoned/failed intubation 0.05-0.35% Abandoned/failed intubation 0.05-0.35% 1,31,3
‘‘can’t intubate, can’t ventilate’ 0.0001-0.02% can’t intubate, can’t ventilate’ 0.0001-0.02% 33
CEMD 2000-2002 half the anaesthetic CEMD 2000-2002 half the anaesthetic deaths caused by failed intubation (3 out of deaths caused by failed intubation (3 out of 6) 6) 11
Risk Factors can be Identified Risk Factors can be Identified History History
Of a difficult airway Of a difficult airway previouslypreviously
Congenital conditionsCongenital conditions Medical conditionsMedical conditions Surgical conditionsSurgical conditions
Examination Examination Prominant teethProminant teeth Inability to mouth Inability to mouth
openopen Inability to extend Inability to extend
neckneck Receeding mandible –Receeding mandible –
(beware the beard!!)(beware the beard!!) Body habitusBody habitus
TestsTests
MallampatiMallampati Thyromental Thyromental
distancedistance Incisor gapIncisor gap Protrusion of teethProtrusion of teeth
But....Not particularly But....Not particularly sensitive or specific sensitive or specific in isolationin isolation
Mallampati score with Samsoon and Mallampati score with Samsoon and Young modificationYoung modification
Problems with TestsProblems with Tests Mallampati Mallampati
sensitivity 42-81% sensitivity 42-81% specificity 66-84%specificity 66-84%
Thyromental Thyromental distance –sensitivity distance –sensitivity 62-91% -specificity 62-91% -specificity 25-82% (<6-7cm)25-82% (<6-7cm)
More testsMore tests Wilson – weight, neck movement, incisor gap, Wilson – weight, neck movement, incisor gap,
retroagnathia and incisor appositionretroagnathia and incisor apposition ArneArne Naguib = 4.9504 + (thyrosternal distance x Naguib = 4.9504 + (thyrosternal distance x
1.1003) + (Mallampati score – 2.6076) + 1.1003) + (Mallampati score – 2.6076) + (thyromental distance x 0.9684) + (neck (thyromental distance x 0.9684) + (neck circumference – 0.3966)circumference – 0.3966)
But all these different tests prove there is no But all these different tests prove there is no single test which is reliablesingle test which is reliable
Combined tests increase the chance of Combined tests increase the chance of correct predictioncorrect prediction
Copyright restrictions apply.
Naguib, M. et al. Anesth Analg 2006;102:818-824
Table 2. Simplified Score Model Described by Arne et al
Evidence for their Evidence for their effectiveness effectiveness 11
Naguib model most Naguib model most sensitive 81.4%sensitive 81.4%
Arne model quite Arne model quite sensitive 54.6%sensitive 54.6%
Wilson model poor Wilson model poor sensitivity- 40.2% sensitivity- 40.2% and poor at and poor at correctly predicting correctly predicting difficult airwaydifficult airway
NaguibNaguib Prediction (l) =Prediction (l) = 0.2262 –0.4261 x 0.2262 –0.4261 x
thyromental distance + thyromental distance + 2.5516 x Mallampati 2.5516 x Mallampati score – 1.1461 x score – 1.1461 x incisor gap + 0.0433 x incisor gap + 0.0433 x heightheight
Height and length in cmHeight and length in cmIf l <zero – intubation easyIf l <zero – intubation easyIf l > zero – intubation If l > zero – intubation
difficultdifficult
Action plan for the Predicted Action plan for the Predicted Difficult IntubationDifficult Intubation
Do they need a GA?Do they need a GA? Do they need to be intubated?Do they need to be intubated? Should they have a rapid sequence?Should they have a rapid sequence? What if I can’t ventilate them on an LMA?What if I can’t ventilate them on an LMA? The action plan will largely depend on why The action plan will largely depend on why
they are a predicted difficult intubation – eg they are a predicted difficult intubation – eg simple difficult laryngoscopy in a normal bmi simple difficult laryngoscopy in a normal bmi normal anatomy patient vs airway tumour with normal anatomy patient vs airway tumour with stridor and distorted anatomystridor and distorted anatomy
The Unpredicted ScenarioThe Unpredicted Scenario Commonest in patients who are Commonest in patients who are
‘apparently’ normal‘apparently’ normal Invariably seems to occur at night and Invariably seems to occur at night and
on your ownon your own Key pointsKey points
Don’t panic!Don’t panic!Optomise patient positionOptomise patient positionLong/McCoy blade and bougieLong/McCoy blade and bougie2nd look2nd look
The ‘difficult laryngoscopy’ scenarioThe ‘difficult laryngoscopy’ scenario
Stay calmStay calm Call for helpCall for help Why is the view poor?Why is the view poor?
PositionPosition EquipmentEquipment cricoidcricoid
Oxygenation is now the Oxygenation is now the prioritypriority
Hand ventilate (keep cricoid Hand ventilate (keep cricoid on) on 100% O2 +/- Guidelon) on 100% O2 +/- Guidel
If you can oxygenate them – If you can oxygenate them – panic over and Decide:panic over and Decide: Do they need Ga?Do they need Ga? Can they be Can they be
ventilated/breathe ventilated/breathe spontaneously on LMA?spontaneously on LMA?
The failed intubation drillThe failed intubation drill This is for when you have had a 2This is for when you have had a 2 ndnd look look
in optimal position with a McCoy blade, in optimal position with a McCoy blade, can’t see anything resembling can’t see anything resembling identifiable structures and you can’t identifiable structures and you can’t hand ventilate them with a mask and hand ventilate them with a mask and simple oro – or naso-pharyngeal airway.simple oro – or naso-pharyngeal airway.
The key is to proceed quickly, The key is to proceed quickly, methodically but calmly until you can methodically but calmly until you can oxygenateoxygenate
Summary Summary Assess carefullyAssess carefully Allow yourself time to planAllow yourself time to plan Don’t anaesthetise them Don’t anaesthetise them
alonealone Have a backup planHave a backup plan Don’t give the muscle Don’t give the muscle
relaxants before checking relaxants before checking hand ventilationhand ventilation
Think of alternatives to a GAThink of alternatives to a GA Stay calm Stay calm Know your emergency airway Know your emergency airway
kit before you need it!!kit before you need it!!
Questions?Questions?
References References 1.1. ‘ ‘Predictive Performance of Three Multivariate Predictive Performance of Three Multivariate
Difficult Tracheal Intubation Models: A Double-Difficult Tracheal Intubation Models: A Double-Blind, Case-Control Study’ M. Naguib et al; Blind, Case-Control Study’ M. Naguib et al; Anaesthesia and Analgesia 2006;102:818-824Anaesthesia and Analgesia 2006;102:818-824
2.2. Difficult Airway Society Guidelines-Failed Difficult Airway Society Guidelines-Failed Intubation 2004Intubation 2004
3.3. University New South Wales: Medical education University New South Wales: Medical education files – intubationfiles – intubation
4.4. ‘‘Prediction and management of difficult tracheal Prediction and management of difficult tracheal intubation’ World Anaesthesia 1998intubation’ World Anaesthesia 1998
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