Slideshare friendly version of my Upper Airway Ultrasound talk from North West Airway Meeting 2021

1. Ultrasound and the Upper Airway
Tom Miller
Consultant Anaesthetist
Liverpool University Hospitals NHS Foundation Trust

2. Objectives
To highlight Ultrasound (US) techniques related to the Upper
Airway that are:
Clinically useful (essential)
Clinically useful in specific circumstances / with
potential for the future
Other things you might hear about

3. USabcd.org (free for RAUK/ESRA members)
Gastricultrasound.org
FUSIC accreditation – ICS

4. Potential Uses
 Locating the CTM
 Percutaneous dilatational tracheostomy
 Airway and ETT sizing (Paeds / subglottic stenosis)
 ETT placement
 Left side DLT sizing
 Probability of OSA
 Predicting post extubation stridor
 Assessing / predicting difficult airway
 Vocal cord movement / palsy
 Evaluation of the epiglottis
 LMA confirmation
 Superior laryngeal nerve block

5. Clinically useful (essential)
• Locating the CTM
• Percutaneous dilatational tracheostomy

6. Locating the cricothyroid membrane
Why do it?
 CICO FONA
 Topicalisation for AFOI
 Awake placement of cannula cricothyroidotomy
 Awake cricothyroidotomy
OK – but why bother with US?

7. CTM
 36% of real emergency airway
access attempts performed by
anaesthetists are successful
 Inability to identify the CTM is
an important factor in this
 Inspection and palpation
techniques in the obese shown
to be 0-39% correct
 Recent meta-analysis (BJA) shows US
approach has a significantly higher
success rate
 100% success of CTM identification
with US in mixed BMI subjects
(83% in morbidly obese- BMI 45)
 Cadaveric cannulation of CTM 44% by
palpation -> 83% US
 Cadaveric trocar cricothyrotomy 39% -
> 63% with US

8. Reduce Mental Load
 Makes FONA (CICO Rescue) in CICO situation part of the plan rather than
“saving from failure”
 Therefore..reduces time without oxygenation
 When scanned with patient awake, opens communication with patient
about possibility of FONA
Marking of the membrane is unaffected by changing neck positions i.e. from
extended to intubating position and back again

9. How to do it?
Transverse
Faster
Easier to learn for the non-
US orientated (my
opinion)
Longitudinal
Cricotracheal and Inter-
tracheal interspace
identification
Perc tracheostomy
Children
Tumour around CTM

10. Br J Anaesth, Volume 117, Issue suppl_1, September 2016, Pages i39–i48
The Transverse TACA method
(‘Thyroid cartilage–Airline–Cricoid cartilage–Airline=TACA’)

11. Br J Anaesth, Volume 117, Issue suppl_1, September 2016, Pages i39–i48,.
The Longitudinal ‘String of pearls’ method

12. Demonstration Video
https://vimeo.com/manage/videos/548797567

13. CTM US
Summary
 Quick
 Effective
 Easy to learn
 Better for your patient

14. Percutaneous dilational tracheostomy
 Selection of optimal
intercartilaginous space – 24%
change in site with US
 Distance from skin to anterior
tracheal wall
 Visualisation of blood vessels
 Possible to use pre- procedure
or during, to guide needle
placement in real time

15. Clinically useful in certain circumstances /
Potential for the future
• Airway and ETT sizing (Paeds / subglottic stenosis)
• ETT placement
• Left side DLT sizing
• Probability of OSA
• Post extubation stridor
• Assessing / predicting difficult airway

16. Airway diameter / ETT Sizing
 US validated against MRI and CT
 Subglottic stenosis
 Paeds:
 Subglottic transverse diameter (US)
correlates with outer diameter of
ETT (cuffed)
 Equation based formula in uncuffed
ETT
 Superior to age and height - based
formula Doi: 10.5152/TJAR.2016.60420

17. Successful ETT placement
 Is it in the trachea?
 Is it in the oesophagus?
 ETT can be visualized within the
trachea in transverse or longitudinal
plane
 Sens 98% Spec 98%
 Oesophagus can be visualized on US –
shouldn’t have an ETT in it
 Sens 93% and Spec 97%
 Useful where C02 less reliable ?
Cardiac arrest / secretions / failure
www.aliem.com/ultrasound-for-verification-of-endotracheal
Doi: 10.1186/s40560-016-1074-z

18. Left sided DLT
 Correlation between tracheal width
(OD) measured just above
sternoclavicular joints and left
bronchus allowing for estimation of
correct LDLT (0.68)
 Although… comparable to using a
CXR (75%)
https://doi.org/10.1016/j.jclinane.2007.11.002

19. OSA
 Distance between lingual arteries
correlated to presence of OSA
 >30mm (RR 2.78) of moderate-severe
OSA (AHI >15)
 Sens 80%, Spec 67%
 STOPBANG
 AHI 15 = Sens 74%, Spec 53%
 AHI 30 = Sens 80%, Spec 49%
 Dynamic scanning of retro-palatial
diameter with predictive model (Sens
100% Spec 65%)
doi: 10.1177/000348940911800304

20. Post extubation stridor
 US may be able to help predict
extubation failure based on air column
width at the level of the vocal cords
before and after cuff deflation related to
post extubation stridor (Medical ICU)
 “Cuff leak test”
 Attempts to quantify cutoff values non-
reproducible
10.1183/09031936.06.00029605

21. Assessing the difficult airway
 Six criteria:
 Tongue thickness >60mm
 Hyomental distance <52+/-6mm
 Hyomental ratio <1.1
 Soft tissue thickness at hyoid >16.9mm
 Soft tissue thickness at thyroid membrane
>34.7mm
 Condylar translation <10mm

22. Macroglossia
Cervical spine mobility
Pre-glottic tissue thickness
Mouth opening

23. Tongue thickness
 Tongue thickness of >61mm an
independent predictor for
difficult intubation
 Sens 75%, Spec 72%
 Tongue volume not predictive
but..
 Ratio of tongue thickness :
thyromental distance > 0.87
shows improvement to:
 Sens 84%, Spec 79%
doi: 10.1093/bja/aex051

24. Hyomental Distance (Ratio)
 Quantifiable measure of cervical spine mobility during hyperextension
 Measure of hyomental distance in neutral and hyperextended position
 Ratio >1.1 – Difficult laryngoscopy (C+L 3/4)
DOI 10.1007/s13244-014-0309-5

25. Pre-glottic soft tissues
 Greater distance of skin to larynx at
various levels associated with increased
probability of difficult airway
 Conflicting results at vocal cords and loss
of PPV at BMI > 35
 At hyoid or thyrohyoid membrane more
promising but need further work to define
cutoffs

26. Condylar translation
 Aka: Mouth Opening
 Translation <10mm an
independent predictor
of difficult laryngoscopy
 Sens 81%, Spec 91%
 PPV 0.45
Yao et al. Anaes Analg 2017;124:800-6

27. Difficult airway assessment
The future is ultrasound?
 Notoriously difficult to predict difficult airways
 In experienced hands full US assessment can be done in few
minutes
 Combination of approaches more powerful than one single
measurement
 No suggestion that this should become common practice as
evidence not there yet
 But… keep an open mind (and a nearby US machine)

28. The Others…

29.  Vocal cord movement
 Pre / post neck surgery for sup. laryngeal nerve function
 Visualization best in young females
 LMA placement
 In 31 children US grade of LMA position correlated (r=0.92) with fibreoptic
confirmation
 Grading system based on arytenoid elevation may be useful for malrotation
 Epiglottis
 Epiglottis can be assessed with US and there may be discernable difference in
epiglottitis but small sample sizes studied to date
 Superior laryngeal nerve block
 Thyrohyoid membrane and superior laryngeal artery can be identified
 Hockey stick transducer

30. In Conclusion:
 Lots of potential uses
 Some really good
techniques to have in
your tool kit
 Exciting developments
for the future
 Ultrasound is non-
invasive, non-
radiating and
reasonably easily
available

31. Resources
CTM
Kristensen, Teoh, Rudolph et al. Ultrasonographic identification of the cricothyroid membrane: best evidence, techniques and clinical impact. Anaesthesia
2016,71,675-683.
Kristensen, Teoh and Rudolph. A randomized cross-over comparison of the transverse and longitudinal techniques for ultrasound-guided identification of the
cricothyroid membrane in morbidly obese subjects BJA 2016,117(S1):i39-i48.
Kristensen, Teoh. Ultrasound identification of the cricothyroid membrane: the new standard in preparing for front-of-neck airway access. BJA 2021;126(1):22-27.
Hung, Chen, Lin and Sun. Comparison between ultrasound-guided and digital palpation techniques for identification of the cricothyroid membrane: a meta-
analysis. BJA 126(1)E9-11.
Malin, Curtis, Dawson et al. Accuracy of ultrasound-guided marking of the cricothyroid membrane before simulated failed intubation. AJEM 2014;32:61-3
Reviews
Kristensen, Teoh and Graumann. Ultrasonogrpahy for clinical-decision making and intervention in airway management: from mouth to lungs and pleurae.
Insights Imaging 2014;5:253-279
Zetlaoui. Ultrasonography for airway management. Anaesth Crit Care Pain Med 2021. 100821
Kong and Teoh. Point-of0care ultrasound (POCUS) of the upper airway. Can J Anaesth 2018;65:473-484.
Osman and Sum. Role of upper airway ultrasound in airway management. Journal of Intensive Care 2016;4:52.
Fulkerson, Moore, Anderson and Lowe Jr. Ultrasonography in the preoperative difficult airway assessment. J Clin Monit Comput 2016. doi:
10.1007/s10877-016-9888-7