Ultrasonic Assessment of the Cricothyroid Membrane

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Ultrasonic Assessment of the Cricothyroid
Membrane

• Better than Landmarking?

Dr ZHANG Jinbin MMED (Anaes) Consultant Department
of Anaesthesiology, Intensive Care and Pain
Medicine Tan Tock Seng Hospital, Singapore
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Outline

• Anatomy
• Locating the cricothyroid membrane (CTM) using
  ultrasound
• Limitations of landmark palpation
• Is ultrasound useful?

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Why is the Cricothyroid Membrane (CTM) important?

• Surgical airway access
• Transtracheal injection of LA

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Anatomy of the CTM
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Conventionally

• Landmark Technique
• Between the thyroid and cricoid cartilages

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Limitations of Palpation

• Poorly discernible landmarks
• Thick neck
• Thick subcutaneous tissue
• Obese patients
• Females
• Distorted anatomy
• Previous radiotherapy to neck
• Tracheal deviation due to head neck tumours
• Infection

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Landmark palpation is inaccurate

• 6 volunteers
• BMI from 24-53kg/m2
• 18 participants
• 30 within defined area
• 10 on target
• 51 missed above
• 35 missed below

Elliot et al. Anaesthesia 2010 65
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Landmark palpation is inaccurate

• 56 females, child-bearing age
• 15 obese (mean BMI 40.5 9.9 kg/m2)
• 24 participants
• 17 anesthesiologists
• 7 OB/GYN trainees
• Neutral
• 25 in non-obese
• 0 in obese group
• Hyperextended
• 29 vs 6

Aslani et al. Anesth Analg 2012114
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• Range of values extensive
• Ease of ultrasonic assessment did not differ with
  BMI

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Landmark palpation is inaccurate

• NAP 4 study
• 15/29 (52) of the cricothyroidotomies performed
  by anaesthetists failed
• 100 success in those done by surgeons

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How can Ultrasound help us?
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Ultrasound Tissue air interface
M.S Kristensen, W.H.L Teoh. Airway Management 1st
Edition, Springer 2014
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Advantages

• Safe
• Quick
• Reproducible
• Non-invasive
• Portable
• Available by bedside
• Gives dynamic images

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Localize Cricothyroid membrane
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Ultrasound Helps

• Ease of image acquisition not affected by BMI
• Quick image acquisition
• 24.32s 20.18s (95 CI 18.59 30.05)
• Poorly discernible landmarks
• Easier to locate CTM, retention of training

Nicholls et al. Am J Emerg Med 200826
Barbe et al. Ann Fr Anesth Reanim 2014 33
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Limitations of Ultrasound

• Expertise
• Subcutaneous air image interference
• Preparation and boot-up time?
• Role for Emergency CICO?
• Minimum training required?