1. 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

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

3. Surgical airway access Surgical airway access Transtracheal injection of LA Transtracheal injection of LA Why is the Cricothyroid Membrane (CTM) important?

4. Anatomy of the CTM

5. Conventionally… Superior Thyroid artery Superior Laryngeal artery Cricothyroid artery Landmark Technique Landmark Technique Between the thyroid and cricoid cartilages Between the thyroid and cricoid cartilages

6. Limitations of Palpation Poorly discernible landmarks Poorly discernible landmarks Thick neck Thick neck Thick subcutaneous tissue Thick subcutaneous tissue Obese patients Obese patients Females Females Distorted anatomy Distorted anatomy Previous radiotherapy to neck Previous radiotherapy to neck Tracheal deviation due to head & neck tumours Tracheal deviation due to head & neck tumours Infection Infection

7. Landmark palpation is inaccurate 6 volunteers 6 volunteers BMI from 24-53kg/m 2 BMI from 24-53kg/m 2 18 participants 18 participants 30% within defined area 30% within defined area 10% on target 10% on target 51% missed above 51% missed above 35% missed below 35% missed below Elliot et al. Anaesthesia 2010; 65

8. Landmark palpation is inaccurate 56 females, child-bearing age 56 females, child-bearing age 15 obese (mean BMI 40.5 + 9.9 kg/m 2 ) 15 obese (mean BMI 40.5 + 9.9 kg/m 2 ) 24 participants 24 participants 17 anesthesiologists 17 anesthesiologists 7 OB/GYN trainees 7 OB/GYN trainees Neutral: Neutral: 25% in non-obese 25% in non-obese 0% in obese group 0% in obese group Hyperextended: Hyperextended: 29% vs 6% 29% vs 6% Aslani et al. Anesth Analg 2012:114

9. Range of values extensive Range of values extensive Ease of ultrasonic assessment did not differ with BMI Ease of ultrasonic assessment did not differ with BMI

10. NAP 4 study NAP 4 study 15/29 (52%) of the cricothyroidotomies performed by anaesthetists failed 15/29 (52%) of the cricothyroidotomies performed by anaesthetists failed 100% success in those done by surgeons 100% success in those done by surgeons Landmark palpation is inaccurate

11. How can Ultrasound help us?

12. Ultrasound – Tissue air interface M.S Kristensen, W.H.L Teoh. Airway Management 1 st Edition, Springer 2014

13. Advantages Safe Safe Quick Quick Reproducible Reproducible Non-invasive Non-invasive Portable Portable Available by bedside Available by bedside Gives dynamic images Gives dynamic images

15. Localize Cricothyroid membrane

16. Ultrasound Helps Ease of image acquisition not affected by BMI Ease of image acquisition not affected by BMI Quick image acquisition Quick image acquisition 24.32s + 20.18s (95% CI 18.59 – 30.05) 24.32s + 20.18s (95% CI 18.59 – 30.05) Poorly discernible landmarks Poorly discernible landmarks Easier to locate CTM, retention of training Easier to locate CTM, retention of training Nicholls et al. Am J Emerg Med 2008;26 Barbe et al. Ann Fr Anesth Reanim 2014; 33

17. Limitations of Ultrasound Expertise Expertise Subcutaneous air – image interference Subcutaneous air – image interference Preparation and boot-up time? Preparation and boot-up time? Role for Emergency CICO? Role for Emergency CICO? Minimum training required? Minimum training required?