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Trial registered on ANZCTR


Registration number
ACTRN12617001131347
Ethics application status
Approved
Date submitted
13/07/2017
Date registered
2/08/2017
Date last updated
9/01/2019
Date data sharing statement initially provided
9/01/2019
Date results information initially provided
9/01/2019
Type of registration
Prospectively registered

Titles & IDs
Public title
Trial to compare two airway ultrasonography techniques for speed and accuracy
Scientific title
Comparison of two transverse airway ultrasonography techniques for speed and accuracy to localise the cricothyroid membrane in obese female volunteers
Secondary ID [1] 292423 0
None
Universal Trial Number (UTN)
U1111-1199-2641
Trial acronym
Linked study record

Health condition
Health condition(s) or problem(s) studied:
Difficult cricothyroid membrane localisation (during airway emergency with failure to oxygenate requiring cricothyroidotomy) 304019 0
Condition category
Condition code
Anaesthesiology 303348 303348 0 0
Anaesthetics

Intervention/exposure
Study type
Interventional
Description of intervention(s) / exposure
Volunteers will be exposed to both a new and a known airway ultrasound technique to locate the cricothyroid membrane.

The known airway ultrasound technique is called the "3-Level Technique" and is from Kristensen MS, Teoh WH, Rudolph SS, Hesselfeldt R, Borglum J, Tvede MF. A randomised cross-over comparison of the transverse and longitudinal techniques for ultrasound-guided identification of the cricothyroid membrane in morbidly obese subjects. Anaesthesia. 2016; 71: 675-83). It involves performing transverse airway ultrasonography at the midline of the anterior neck as follows: Aim to start scan at the thyroid cartilage, once the thyroid cartilage is identified then scan caudally over the cricothyroid membrane (CTM), hopefully identifying it on the first pass, but continue scanning caudally until identify the cricoid cartilage, then scan cephaladly until confident over the CTM, then finish. This is expected to take less than 1 minute, in Kristensen's paper it took a mean time of just 24 seconds to identify the CTM. This will be the control for the study to compare the new technique to.

The new technique, called the "2-Level Technique" is a modification of the 3-level technique, which is hoped will be identify the CTM quicker, while being just as accurate. It is a transverse midline ultrasounography technique, performed as follow:: Aim to start at the thyroid cartilage, once the thyroid cartilage is identified then carefully scan caudally until confident over the CTM, then finish. This technique is also expected to take less than 1 minute, likely less than 24 seconds.

Student participants will have the scans performed on them up to 3 times each during the training period (total scan time of up to 6 minutes ultrasonography). Mock patient participants will have the scans performed on them up to 6 times each (total scan time of up to 12 minutes). These total scan times are much less than an obstetric ultrasound in clinical practice, which includes scanning the fetus and can take up to 40 minutes.

On the training day, initially an specialist anaesthetist with much experience in airway ultrasonography with perform some scans on the 5th year medical students to demonstrate the two techniques, then they will practice on each other to gain experience and learn the techniques, which are relatively easy to learn and perform. Then, on the research day, these trained 5th year medical students participants (who will be assessed for accuracy and timing to locate the CTM) will perform the scans on the mock patient participants.

On the research day, each student participant will have perform both techniques once each on a single mock patient participant, with at least 10 minute break between scans. During the 10 minute break though, another student or students may perform their first or second scan.
Intervention code [1] 298597 0
Treatment: Devices
Comparator / control treatment
As discussed above, the known airway ultrasound technique is called the "3-Level Technique" and is from Kristensen MS, Teoh WH, Rudolph SS, Hesselfeldt R, Borglum J, Tvede MF. A randomised cross-over comparison of the transverse and longitudinal techniques for ultrasound-guided identification of the cricothyroid membrane in morbidly obese subjects. Anaesthesia. 2016; 71: 675-83). It involves performing transverse airway ultrasonography at the midline of the anterior neck as follows: Aim to start scan at the thyroid cartilage, once the thyroid cartilage is identified then scan caudally over the cricothyroid membrane (CTM), hopefully identifying it on the first pass, but continue scanning caudally until identify the cricoid cartilage, then scan cephaladly until confident over the CTM, then finish. This is expected to take less than 1 minute, in Kristensen's paper it took a mean time of just 24 seconds to identify the CTM. This will be the control for the study to compare the new technique to.

The new technique, called the "2-Level Technique" is a modification of the 3-level technique, which differs in that it is shorted and is hoped will be identify the CTM quicker, while being just as accurate. It is a transverse midline ultrasounography technique, performed as follow:: Aim to start at the thyroid cartilage, once the thyroid cartilage is identified then carefully scan caudally until confident over the CTM, then finish. This technique is also expected to take less than 1 minute, likely less than 24 seconds.

The 3-level technique will be the comparator (control) for the 2-level technique.
Control group
Active

Outcomes
Primary outcome [1] 302736 0
Time taken (speed) to locate the cricothyroid membrane will be assessed for watch scan by a blinded timing observer. This observer will not watch the scan, but will face the other way. This observer will measure with a stop watch from when the scanning participant says “start” (when the ultrasound transducer contacts the ultrasound transmission gel on skin of the neck) to when they say “done” (when they believe they have located the CTM on the image).
Timepoint [1] 302736 0
At the end of each airway ultrasounography examination (less than 2 minutes per scan)
Secondary outcome [1] 336866 0
Accuracy will be assessed by a single blinded accuracy observer (blinded to which scan technique is performed, and will therefore also not observe the scans being performed). After scans are completed this accuracy observer will assess the accuracy of each student participants' scans by looking at the ultrasound image saved at the completion of each scan, to assess if each image displays the cricothyroid membrane or not.
Timepoint [1] 336866 0
Also at the end of each airway ultrasonography examination.

Eligibility
Key inclusion criteria
Medical student participants: 5th year medical students at University of Tasmania's Launceston Clinical School, must be aged over 18 years of age.

Mock patient participants: must be over 18 years of age and BMI>30
Minimum age
18 Years
Maximum age
No limit
Gender
Both males and females
Can healthy volunteers participate?
Yes
Key exclusion criteria
<18 years, Aboriginal or Torre's Straight Islanders, pregnant, incompetent to give informed consent, hospital inpatients.

Study design
Purpose of the study
Diagnosis
Allocation to intervention
Randomised controlled trial
Procedure for enrolling a subject and allocating the treatment (allocation concealment procedures)
Opaque envelopes
Methods used to generate the sequence in which subjects will be randomised (sequence generation)
Simple randomisation using procedures drawing the mixed up sealed opaque envelopes from a container
Masking / blinding
Blinded (masking used)
Who is / are masked / blinded?


The people assessing the outcomes
Intervention assignment
Crossover
Other design features
Phase
Not Applicable
Type of endpoint(s)
Efficacy
Statistical methods / analysis
The mean time difference will be estimated using repeated-measures mixed effects linear regression, adjusted for order of scan, patient BMI and whether successful identification of CTM occurred.

Accuracy at 27s between the two techniques was compared by time to event analysis. Overall accuracy between the two techniques was compared by logistic regression.

Recruitment
Recruitment status
Completed
Date of first participant enrolment
Anticipated
Actual
Date of last participant enrolment
Anticipated
Actual
Date of last data collection
Anticipated
Actual
Sample size
Target
Accrual to date
Final
Recruitment in Australia
Recruitment state(s)
TAS
Recruitment hospital [1] 8527 0
Launceston General Hospital - Launceston
Recruitment postcode(s) [1] 16621 0
7250 - Launceston

Funding & Sponsors
Funding source category [1] 296979 0
University
Name [1] 296979 0
University of Tasmania
Address [1] 296979 0
Launceston Clinical School,
C/O Launceston General Hospital,
Charles St,,
Launceston, TAS, 7252.
Country [1] 296979 0
Australia
Funding source category [2] 296980 0
Hospital
Name [2] 296980 0
Launceston General Hospital
Address [2] 296980 0
Department of Anaesthesia,
Launceston General Hospital,
Charles St.,
Launceston, TAS, 7252
Country [2] 296980 0
Australia
Primary sponsor type
University
Name
University of Tasmania
Address
Launceston Clinical School,
C/O Launceston General Hospital,
Charles St,,
Launceston, TAS, 7252.
Country
Australia
Secondary sponsor category [1] 295981 0
Hospital
Name [1] 295981 0
Launceston General Hospital
Address [1] 295981 0
Department of Anaesthesia,
Launceston General Hospital,
Charles St.,
Launceston, TAS, 7252
Country [1] 295981 0
Australia

Ethics approval
Ethics application status
Approved
Ethics committee name [1] 298180 0
University of Tasmania Human Research Ethics Committee
Ethics committee address [1] 298180 0
301 Sandy Bay Road,
Sandy Bay
Postal address: Private Bag 01, Hobart TAS 7001
Ethics committee country [1] 298180 0
Australia
Date submitted for ethics approval [1] 298180 0
10/07/2017
Approval date [1] 298180 0
30/08/2017
Ethics approval number [1] 298180 0
H0016662

Summary
Brief summary
In the event of a “can’t intubate, can’t oxygenate” (CICO) event during general anaesthesia, front of neck access (FONA) is definitive management. Faster FONA can reduce morbidity and mortality. Localisation of the cricothyroid membrane (CTM) is necessary for successful FONA. It ideally should be performed before induction in every patient, though in some time critical emergencies there is not the opportunity to do this in an elective fashion. Palpation of landmarks to localise the CTM has been shown to be very inaccurate, particularly in women and obese patients. Ultrasound has been shown to be very accurate, although slower. Ultrasound for procedural guidance has been shown to improve the rate of correct cricothyroidotomy device insertions with fewer complications. This study aims to show primarily if a new 2-level transverse airway ultrasonography technique to localise the CTM is quicker than a known 3-level technique. Accuracy of the technique will also be assessed and compared between the techniques. Scanning participants will be randomised to which technique they perform first, and both timing and accuracy observers will be blinded to which technique is performed.
Trial website
Trial related presentations / publications
(1) https://s3-ap-southeast-1.amazonaws.com/cirrus.capstan.net.au/racs/asc/2018/poster/2936/player.html

(2) https://bjanaesthesia.org/article/S0007-0912(18)31289-3/abstract
Public notes

Contacts
Principal investigator
Name 76238 0
Dr Karl Gadd
Address 76238 0
Department of Anaesthesia,
Launceston General Hospital,
Charles St.,
Launceston, TAS, 7252.
Country 76238 0
Australia
Phone 76238 0
+61 3 67776777
Fax 76238 0
Email 76238 0
karl.gadd@ths.tas.gov.au
Contact person for public queries
Name 76239 0
Dr Karl Gadd
Address 76239 0
Department of Anaesthesia,
Launceston General Hospital,
Charles St.,
Launceston, TAS, 7252.
Country 76239 0
Australia
Phone 76239 0
+61 3 67776777
Fax 76239 0
Email 76239 0
karl.gadd@ths.tas.gov.au
Contact person for scientific queries
Name 76240 0
Dr Karl Gadd
Address 76240 0
Department of Anaesthesia,
Launceston General Hospital,
Charles St.,
Launceston, TAS, 7252.
Country 76240 0
Australia
Phone 76240 0
+61 3 67776777
Fax 76240 0
Email 76240 0
karl.gadd@ths.tas.gov.au

Data sharing statement
Will individual participant data (IPD) for this trial be available (including data dictionaries)?
No
No/undecided IPD sharing reason/comment
CRF data is available if required by law to share.
What supporting documents are/will be available?
Study protocol
Statistical analysis plan
Informed consent form
Ethical approval
Summary results
Have study results been published in a peer-reviewed journal?
Yes
Journal publication details
Publication date and citation/details [1] 963 0
British Journal of Anaesthesia, 2019, 122(2), e28-31.

Published online ahead of print: https://doi.org/10.1016/j.bja.2018.11.008
Other publications
Have study results been made publicly available in another format?
Yes
Other publication details
Citation type [1] 964 0
Conference poster
Citation/DOI/link/details [1] 964 0
https://s3-ap-southeast-1.amazonaws.com/cirrus.capstan.net.au/racs/asc/2018/poster/2936/player.html
Results – plain English summary
The cricothyroid membrane (CTM) is the site of emergency front of neck airway access (cricothyroidotomy) during anaesthesia. Cricothyroidotomy is required when a patient cannot be oxygenated using facemask, laryngeal mask or endotracheal intubation, a rare emergency. Locating the CTM in obese females by palpation can be impossible, whereas ultrasonography is more accurate but slower. We found that a new 2-Level transverse ultrasonography technique is significantly faster than the previously fastest known technique (the “thyroid-airline-cricoid-airline”, TACA, technique) to locate the CTM. We also found that the 2-Level technique is significantly more accurate within 27s (a window of time to perform the scan that is considered to still allow cricothyroidotomy to be performed before morbidity could occur in obese female patients due to low oxygen in the body). Overall accuracy though, not considering time, was not significantly different between the two techniques. So, overall, the 2-Level technique was found to be superior in speed, and in accuracy at 27s. This result was found despite simple randomisation, and one scanning participant’s error (unintentionally performing scans in reverse order to allocation), resulting in a skewed distribution with the 2-Level technique performed initially (before crossover) more (62%) than the TACA (38%), that could possibly favour the TACA technique due to recall bias in this study. Concluding, the 2-Level technique may reduce morbidity in obese female patients during anaesthesia by reducing the time taken from the declaration of an airway emergency until the successful performance of cricothyroidotomy.