Preoperative Assessment of the Airway

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Pre-operative Assessment of the Airway

• SHO in Anaesthesia of 3 months experience

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Scope of presentation

• To supplement the competency based training of
  the novice anaesthetist
• It is not intended to replace clinical
  apprenticeship/ experience gained from direct
  clinical supervision

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Aims of presentation

• To provide the theoretical knowledge for the
  assessment of the patients airway
• To show how assessment affects your airway
  plan(s)
• This should be supplemented by a competency based
  training in clinical practice

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• Is this patients airway going to be difficult to
  manage?
• As an SHO ask yourself
• What skills/knowledge or competencies do I need
  to develop to assess this patients airway?
• How does this assessment lead to an airway
  management plan?

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Your airway assessment leads to an informed
airway management plan

• What happens to our patients airway following
  induction of general anaesthesia?
• How is this managed?

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The upper airway and anaesthesia

• Associated airway obstruction caused by
• Tongue falling back onto posterior pharyngeal
  wall
• Decreased pharyngeal tone leading to the glottic
  airway falling upon the posterior pharyngeal wall

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Management of the airway

• Extend head on neck
• this tensions the anterior neck tissues thereby
  pulling the glottic opening off the posterior
  pharyngeal wall
• Protrude the mandible
• this lifts the tongue from the
  posterior pharyngeal wall

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Managing the airway

• Extend the head

3 separate slides (??)
Extend the mandible
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The upper airway and anaesthesia

• Create a functional air space - artificially
• Oral airway
• Naso-pharyngeal airway
• Laryngeal mask

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The upper airway and anaesthesia

• Upper airway manipulations as described above
  allow a patent airspace from the facemask to the
  patients alveoli
• A similar set of airway manoeuvres is required
  for direct laryngoscopy with the Macintosh
  laryngoscope

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Positioning the patient

• Optimal positioning of the patient for direct
  laryngoscopy

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Positioning the patient

• The patients position is similar whether direct
  laryngoscopy is required or maintenance of the
  airway with a face mask or insertion of a
  laryngeal mask
• Therefore assessing if the three axes of the
  upper airway align tests subsequent airway
  management and direct laryngoscopy

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Head and neck position and the axes of the head,
neck and upper airway 1

• Patient in the neutral position

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Head and neck position and the axes of the head,
neck and upper airway 2

• Lower cervical flexion of around 33 degrees

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Head and neck position and the axes of the head,
neck and upper airway 3

• Atlantooccipital extension of around 80 degrees

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Demonstration of correct positioning of patient
Upper atlanto-occipital extension

• Lower cervical flexion

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Which tests?

• Since the above manoeuvres will be required
  during the general anaesthetic it is necessary
  to confirm that the patients anatomy allow these
  to be performed during your pre-operative
  assessment.
• The degree to which these are compromised will
  determine your airway management plan

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• During the first 6 months of anaesthesia if
  your airway assessment suggests potential
  difficulty seek senior assistance

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The following is a suggested airway assessment
for a novice in their first 3 monthsThe
assessment will evolve as trainees experience of
airway management develop
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Which tests

• Cranio-cervical movement (upper and lower)
• Mouth opening (Mallampati test)
• Jaw thrust
• Examine thyromental distance and space
• Testing for both potential airway and
  laryngoscopic difficulty in your airway
  management strategy

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• Cranio-cervical movement
• Open mouth
• Jaw thrust
• Examine front of neck

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Cranio-cervical junction

• Will you be able to
• Flex the lower cervical vertebrae?
• Atlanto-occipitaly extend the head?
• Nod head fully note the degree of movements in
  relation to what will be required during
  anaesthesia

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Cranio-cervical junction

• Nod head fully looking for gt 90 movement
• Place your hand on back of patients neck ask
  patient to nod head. Your hand immobilises
  patients lower cervical spine, allowing you to
  assess atlanto-occipital movement try it on
  yourself

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Lifting the tongue via a jaw thrust

• Will you be able to lift the tongue?
• Ask your patient
• Can you bite your upper lip with your lower
  jaw?

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Jaw movements

• Inter-incisor gap 3 finger breadths
• Forward thrust of jaw relative lower and upper
  incisor movement
• a Lower in front of upper
• b Edge to edge
• c Cannot touch

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• Will you be able to get into the pharynx?
  

Inter-incisor gap open your mouth relevance
to airway equipment size

Mallampati

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Mallampati

• Tests jaw opening and cranio-cervical junction
  movement
• Either you can see posterior pharyngeal wall or
  not
• But it gives you an impression of the size of the
  tongue

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• Thyromental distance A
• gt 6.0 cm lower risk group
• lt 6.0 cm higher risk group
• Sternomental distance B
• gt 12.5 cm lower risk
• lt 12.5 cm higher risk

The measurements are taken with the head and neck
fully extended
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Examine the front of the neck

• Thyromental distance(Mandibular space
  compliance)
• Cricothyroid membrane and cricoid position

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Other considerations

• Weight gt120 kg
• Note previous history of difficulty
• Note patient populations
• (Diabetes, rheumatoid, OSA)

?
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Which tests again

• Cranio-cervical movement (upper and lower)
• Mouth opening (Mallampati test)
• Jaw thrust
• Examine thyromental distance and space
• Testing for both potential airway and
  laryngoscopic difficulty in your airway
  management strategy

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• 1000 patients prevalence of 1

990 will be easy 10 will be difficult
Higher risk
Lower risk
100 will test positive 7 truly hard
900 will test negative 3 truly hard
Prevalence 0.3 of the group who tested negative
Prevalence 7 of the group who tested positive