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Trial registered on ANZCTR


Registration number
ACTRN12619001288112
Ethics application status
Approved
Date submitted
28/07/2019
Date registered
18/09/2019
Date last updated
18/09/2019
Date data sharing statement initially provided
18/09/2019
Date results information initially provided
18/09/2019
Type of registration
Retrospectively registered

Titles & IDs
Public title
Identifying the cricothyroid membrane in healthy subjects: a comparison of three techniques to assess accuracy, confidence and speed
Scientific title
Identifying the Cricothyroid Membrane in Non-Obese Subjects with Normal Neck Anatomy:
A Comparison of Palpation, Laryngeal Handshake and Ultrasound after Formal Training
Secondary ID [1] 298853 0
None
Universal Trial Number (UTN)
U1111-1237-6010
Trial acronym
Linked study record

Health condition
Health condition(s) or problem(s) studied:
Airway management 313806 0
Condition category
Condition code
Anaesthesiology 312217 312217 0 0
Anaesthetics

Intervention/exposure
Study type
Interventional
Description of intervention(s) / exposure
BRIEF NAME
Identifying the location of the cricothyroid membrane (CTM) with three methods: palpation, laryngeal handshake and ultrasound.

All work was undertaken at the School of Medicine, University of St Andrews, UK.

FULL EXPLANATION
Operator Recruitment and Training:
Six operators were recruited to undergo training and evaluation in identifying the CTM on simulated patients (SPs). Three of the operators were anaesthetists from Ninewells Hospital, Dundee, and three were medical students from the School of Medicine, University of St Andrews. All anaesthetists (mean age 33 years, min-max range 30 - 34 years), were in an anaesthesia specialty training post recognised by the Royal College of Anaesthetists. Two were female, with seven and eight years of anaesthesia experience respectively. One was male, in his first year of anaesthesia training. All had previously undergone training in the use of ultrasound (although not relating to eFONA), and regularly use it to place venous central lines and perform regional anaesthesia techniques. All medical students (mean age 21 years, min-max range 20 - 23 years) were in their first three years of medical school, and none had any previous formal training or experience in using ultrasound. The operators attended a three hour educational tutorial on identifying the CTM, provided by a group of experienced anaesthetists (three consultants, two registrars in their fifth year of training). This began with a 30 minute presentation to summarise the aims of the study, the scenario of CICO and eFONA, and a review of the relevant anatomy using models and images. The ultrasound assessment using a 6 - 12 MHz linear array ultrasound probe (LOGIQ V2; GE Healthcare). Finally, all three techniques were demonstrated in real time on a member of the study investigator group. Operators were directed to learn them in this stepwise manner and maintain this approach throughout the study, using the following steps for each technique:
- Palpation: identify sternal notch; identify laryngeal prominence; identify CTM; mark CTM
- Laryngeal handshake: identify greater cornu of the hyoid (roll side-side); identify thyroid laminae; identify cricoid cartilage (middle finger and thumb); identify CTM (index finger); mark CTM
- Ultrasound: identify sternal notch; place ultrasound probe transversely above the notch; slide the probe to the SP's right and rotate 90 degrees; identify 'string of pearls' (tracheal cartilages); move probe superiorly to identify CTM; mark CTM.

For consistency, operators were instructed to carry out all techniques with their non-dominant hand (as the dominant hand would be ready to perform tracheal access when undertaking eFONA).

During the subsequent two hours a mastery learning approach was used to provide the operators with extensive, structured iterative practice, identifying the trachea and CTM on other members of the tutorial group under the direct supervision of study investigators. They were each able to assess over 20 individuals (each other and other medical students from the University of St Andrews) for each technique. In the final 30 minutes of the tutorial, operators were able to practise and familiarise themselves with the technique to be used in the subsequent assessment phase - namely, using the three techniques to identify the CTM and placing markers on the skin in the manner required during the later assessment phase.

SP Recruitment
12 SPs were recruited from the University of St Andrews, School of Medicine, simulated patient pool. As the traditional methods of palpation and laryngeal handshake are known to carry a lower success rate in females, all SPs were women. No SPs had any known pathology affecting their anterior neck.

Operator Assessment of SP CTM:
The SPs subsequently moved through a series of six stations where their neck was assessed by all operators trained in stage one (three anaesthetists and three medical students). The SP moved through this series of stations three times, so each operator assessed the neck of each SP three times (once with each technique: palpation, laryngeal handshake or ultrasound). The order of the techniques used was randomised, to minimise the effect of operator familiarity with any given technique or SP’s neck. For each assessment, the operators were allowed three minutes (180 seconds) to position the SP (in the extended eFONA position), assess the neck with one of the techniques and identify the central point of the CTM, then mark this point by applying the 5 mm sticker to the skin. The pre-marked transparent dressing was then reapplied to the front of the SP’s neck by an independent assessor (aligned with the identifier markings: see below - 'comparator/control treatment'), and the sticker position compared to the experts’ markings, with the operator blinded to the result. If the centre of the 5 mm sticker lay within the experts’ marks of the upper and lower boundaries of the CTM, this was categorised as successful. Similarly, if the central point of the sticker lay within 5 mm either side of the midline over the CTM, this was also deemed successful. In all cases, the distance from the centre of the sticker to the central point of the CTM (as identified by the experts and marked on the dressing) was measured in the axial (superior/inferior) and sagittal (lateral, either side of midline) planes, and recorded to the nearest millimetre. The operator was then asked to assess their confidence in each technique using a linear numerical scale (0 = no confidence, 10 = extremely confident). Each time the neck was assessed, the operator was timed from the point they first touched the SP’s neck (with their hand or the ultrasound probe) to the time they placed the sticker on the skin. The time was recorded to the nearest second (sec).

Second Expert Assessment of SP CTM (Distance from Suprasternal Notch to Centre of CTM and Consistency of Mark Position with Changing Neck Position):
Finally, the same experts repositioned each SP into the position optimal for eFONA once again, and reassessed the central point of the CTM using palpation and ultrasound. The point was marked on the skin with permanent marker pen and the distance from suprasternal notch was measured (to the nearest mm). The SP then moved off the table and sat whilst other SPs were assessed (to alter the position of the head and neck, and underlying laryngeal/pharyngeal structures). The SP was reassessed (for a final time), using the same method and experts, again in the extended position. The previous skin mark indicating the central point of the CTM was assessed in relation to the upper and lower boundaries of the CTM, to determine if it still lay within the boundaries of the CTM after changing position. The distance from the suprasternal notch to the centre of the CTM was again measured (to the nearest mm). The difference in these distances (before and after changing position and repositioning) was recorded.
Intervention code [1] 315120 0
Treatment: Other
Comparator / control treatment
Expert Assessment of CTM (Centre and Upper/Lower Boundaries):
Initially, the SP’s neck was assessed by two ultrasound experts (one a consultant anaesthetist and one an ST 6 in anaesthesia), both of whom had taught the operators during the preceding tutorial. The SP was placed in the extended head and neck position recommended for eFONA by the DAS guidelines for unexpected difficult intubation in adults. Using a combination of palpation and ultrasound for each SP, and the same techniques taught in the operators’ tutorial, the experts identified the CTM and used the ‘freeze’ function on the ultrasound machine to obtain a still image. The size of the CTM (distance between the superior boundary (inferior border of thyroid cartilage) and inferior boundary (superior border of cricoid cartilage) was measured to the nearest millimetre (mm), using the software measurement tool. The central point of the CTM was then identified using a technique previously described, and marked with a 5 mm diameter circular sticker. The position of the sticker was confirmed by ultrasound before a transparent, mouldable polyurethane membrane was applied over the skin (two 3M Tegaderm film dressings ®, which had been prepared previously by applying the adherent surfaces together, with the outer border of removable paper left in place to prevent the material stretching). On this was marked the central point of the CTM, over the central point of the underlying sticker on the skin. The superior and inferior margins of the CTM were marked by taking the height of the CTM in millimetres (as measured above), and marking a line at half of that distance below the central point and half the distance above. The position and orientation of the dressing were indicated by identifier markings on the edges and surrounding skin of the neck, so it could be removed and later re-applied to the same location (indicating the centre, upper and lower boundaries of the CTM).

Ultrasound (US) was used as the reference 'comparator' technique for the assessment of operator performance as, in the literature, it has been shown to have the highest success rate. The statistical analysis was therefore based on comparing previously published success of US:palpation and US:laryngeal handshake.
Control group
Active

Outcomes
Primary outcome [1] 320856 0
Which technique allows operators to identify the CTM most accurately?

(This will be assessed by comparing the location of the CTM, identified by the operators, to the expert assessment by two ultrasound experts (one a consultant anaesthetist and one an ST 6 in anaesthesia). Identification of the CTM will be considered accurate (successful) if the operator's mark is within the upper and lower boundaries of the CTM as judged by the experts, and within 5 mm either side of the experts' mark of the midline.)
Timepoint [1] 320856 0
Participant accuracy will be determined immediately after they complete each neck assessment. It will then be collated, evaluated and compared at the end of the study (during data analysis).
Primary outcome [2] 320857 0
Which technique allows operators to identify the CTM most confidently?

(This will be assessed by asking the operators, after they have completed each front of neck assessment to mark the CTM, to rate their confidence in the technique on a scale 0 - 10.)
Timepoint [2] 320857 0
Data will be collected on this immediately after completion of each neck assessment, then evaluated and compared at the end of the study during data analysis.
Primary outcome [3] 320858 0
Which technique allows operators to identify the CTM most quickly?

(This will be assessed by timing the operators using a stop watch when they assess the front of neck. The stopwatch will be started from the point they first make contact with the simulated patient's neck and stopped when they place the marker sticker on the neck.)
Timepoint [3] 320858 0
Data will be collected on this for the duration of each neck assessment, then evaluated and compared at the end of the study during data analysis.
Secondary outcome [1] 373108 0
Determine the distance from the suprasternal notch to the CTM midpoint in the eFONA position.

(This will be assessed by the positioning the simulated patients in the position required for eFONA and marking the location of the suprasternal notch on the skin. The centre of the CTM will be identified by experts, using ultrasound, and the distance between these marks will be measured.)
Timepoint [1] 373108 0
This data will be collected immediately after each neck assessment. It will then be collated, evaluated and compared at the end of the study (during data analysis).
Secondary outcome [2] 373109 0
Determine the vertical height of the CTM as measured on ultrasound.

(This will be assessed by two experts: with the simulated patient in the eFONA position, the CTM will be assessed using ultrasound, and the upper and lower boundaries marked. The distance between these boundaries will then be measured.)
Timepoint [2] 373109 0
This data will be collected immediately after each neck assessment. It will then be collated, evaluated and compared at the end of the study (during data analysis).
Secondary outcome [3] 373110 0
Determine whether the skin marking over the CTM maintains its position with respect to the true CTM location, as measured by experts using ultrasound, after changing position of the neck.
Timepoint [3] 373110 0
This data will be collected immediately after each neck assessment. It will then be collated, evaluated and compared at the end of the study (during data analysis).

Eligibility
Key inclusion criteria
Inclusion Criteria (Operators):
- Anaesthetists at Ninewells Hospital, Department of Anaesthesia
- Medical students at St Andrews University, School of Medicine

Inclusion Criteria (Simulated Patients):
- Female
- Adults (aged >17 years)
- Ability to consent
Minimum age
18 Years
Maximum age
No limit
Gender
Both males and females
Can healthy volunteers participate?
Yes
Key exclusion criteria
Exclusion criteria (Operators):
- Non-attendance at the initial study tutorial
- Prior training in use of ultrasound for emergency front of neck access
- Prior training in general use of ultrasound (medical student)

Exclusion criteria (Simulated Patients):
- Previous surgery, radiation or major pathology of the neck anterior to the vertebral column that distorts the soft tissue anatomy (e.g. thyroid tumour, but not dermatitis/abrasions)
- Inability to extend neck
- Inability to identify the CTM or trachea by the experts prior to assessment by operators

Study design
Purpose of the study
Educational / counselling / training
Allocation to intervention
Non-randomised trial
Procedure for enrolling a subject and allocating the treatment (allocation concealment procedures)
Not applicable: all operators assessed all simulated patients.
Methods used to generate the sequence in which subjects will be randomised (sequence generation)
N/A
Masking / blinding
Open (masking not used)
Who is / are masked / blinded?



Intervention assignment
Other
Other design features
All simulated patients were assessed with all techniques. The order of the techniques used by operators was randomised using a randomisation table created by computer software (i.e. computerised sequence generation).
Phase
Not Applicable
Type of endpoint(s)
Efficacy
Statistical methods / analysis
Sample Size
Recent similar work on the palpation and laryngeal handshake techniques determined a success rate of 33% for palpation and 62% for laryngeal handshake. A previous publication by a member of this study group was used as the standard success rate of ultrasound: in a randomised cross-over comparison, ultrasound achieved 90% success. These figures are broadly consistent with preliminary data collected by other members of this study group during pilot work in Ninewells Hospital, Dundee, UK. This demonstrated 37.5% success in identifying the cricoid cartilage by palpation and 100% for ultrasound, with a mean (±SD) distance (mm) from the expert’s location to the operator’s location of 8.8 (±7.9) and 1.5 (±1.9) respectively. A priori calculation of sample size for detection of a statistically significant difference between any two assessments, with Alpha (type I) error = 0.05 and Beta (type II error) = 0.8 was performed, comparing ultrasound (90% success) to palpation (33%) and then ultrasound (90%) to laryngeal handshake (62%). Based on this, a minimum of 20 (ultrasound:palpation) or 35 (ultrasound:laryngeal handshake) assessments were required for the study. By assessing 12 SPs with three operators in each limb (anaesthetist and novice/medical student) for each technique, we planned to collect 36 assessments by each group of operators for each technique (and 72 in total for each technique).

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 outside Australia
Country [1] 21717 0
United Kingdom
State/province [1] 21717 0
Fife

Funding & Sponsors
Funding source category [1] 303401 0
Charities/Societies/Foundations
Name [1] 303401 0
Scottish Airway Group
Address [1] 303401 0
C/O Simon Crawley
Department of Anaesthesia
Level 6, Ninewells Hospital
Dundee
DD1 9SY
Country [1] 303401 0
United Kingdom
Primary sponsor type
Individual
Name
James Bowness
Address
Department of Anaesthesia
Level 6, Ninewells Hospital
James Arrott Drive
Dundee
DD1 9SY
Country
United Kingdom
Secondary sponsor category [1] 303443 0
Individual
Name [1] 303443 0
Alexander Le Saint-Grant
Address [1] 303443 0
School of Medicine
Medical & Biological Sciences Building
University of St Andrews
St Andrews
KY16 9TF
Country [1] 303443 0
United Kingdom
Other collaborator category [1] 280871 0
Individual
Name [1] 280871 0
Alasdair Taylor
Address [1] 280871 0
Department of Anaesthesia
Level 6, Ninewells Hospital
James Arrott Drive
Dundee
DD1 9SY
Country [1] 280871 0
United Kingdom
Other collaborator category [2] 280872 0
Individual
Name [2] 280872 0
Andrew Dalton
Address [2] 280872 0
Department of Anaesthesia
Level 6, Ninewells Hospital
James Arrott Drive
Dundee
DD1 9SY
Country [2] 280872 0
United Kingdom
Other collaborator category [3] 280873 0
Individual
Name [3] 280873 0
Simon Crawley
Address [3] 280873 0
Department of Anaesthesia
Level 6, Ninewells Hospital
James Arrott Drive
Dundee
DD1 9SY
Country [3] 280873 0
United Kingdom
Other collaborator category [4] 280874 0
Individual
Name [4] 280874 0
Fraser Chisholm
Address [4] 280874 0
School of Medicine
Medical & Biological Sciences Building
University of St Andrews
St Andrews
Fife
KY16 9TF
Country [4] 280874 0
United Kingdom
Other collaborator category [5] 280875 0
Individual
Name [5] 280875 0
Ourania Varsou
Address [5] 280875 0
Anatomy Facility
School of Life Sciences
University of Glasgow
Thomson Building
University Avenue
Glasgow
G12 8QQ
Country [5] 280875 0
United Kingdom
Other collaborator category [6] 280876 0
Individual
Name [6] 280876 0
Wendy Teoh
Address [6] 280876 0
Private Anaesthesia Practice
Wendy Teoh Pte Ltd
KK Women's and Children's Hospital
100 Bukit Timah Road
Singapore
229899
Country [6] 280876 0
Singapore
Other collaborator category [7] 280877 0
Individual
Name [7] 280877 0
Michael Kristensen
Address [7] 280877 0
Department of Anaesthesia
Rigshospitalet
University Hospital of Copenhagen
Blegdamsveg 9
2100
Country [7] 280877 0
Denmark
Other collaborator category [8] 280878 0
Individual
Name [8] 280878 0
Barry McGuire
Address [8] 280878 0
Department of Anaesthesia
Level 6, Ninewells Hospital
James Arrott Drive
Dundee
DD1 9SY
Country [8] 280878 0
United Kingdom

Ethics approval
Ethics application status
Approved
Ethics committee name [1] 303930 0
University of St Andrews, School of Medicine, Ethics Committee
Ethics committee address [1] 303930 0
Dr Robert Humphries
School of Medicine
Medical & Biological Sciences Building
University of St Andrews
St Andrews
Fife
KY16 9TF
Ethics committee country [1] 303930 0
United Kingdom
Date submitted for ethics approval [1] 303930 0
06/02/2019
Approval date [1] 303930 0
14/03/2019
Ethics approval number [1] 303930 0
MD14170

Summary
Brief summary
Aims
1. Compare the accuracy, confidence and speed in assessing the cricothyroid membrane (CTM) of simulated patients (SPs) with three techniques (conventional palpation, laryngeal handshake, ultrasound) by two groups of operators (anaesthetists vs medical students).
2. Determine the distance from the suprasternal notch to the CTM, size of CTM, and whether skin markings of the CTM (when identified and marked by experts using ultrasound) maintain their position with respect to the CTM after time, manipulation and changing position of the neck

Background and Rationale
‘Emergency front of neck access’ (eFONA) is not always successful due to an inability to correctly identify the CTM or inability to access the trachea after appropriate identification of structure. The most common techniques to identify structures at the front of the neck are palpation and laryngeal handshake. However, these techniques are not 100% accurate and recent accounts describe greater success with ultrasound. This is a prospective pilot study to evaluate these three methods performed by anaesthetists and non-anaesthetists.

Study Design
Operators (anaesthetists and medical students) attended a three hour tutorial which summarised the relevant anatomy (using models and cadavers) and the three techniques to identify the CTM. The majority of the tutorial was spent practising the techniques, identifying the trachea and CTM multiple times on multiple people for each technique. Operators then assessed the location of the CTM on 11 SPs* three times: once with each technique. Each assessment was separated by time and the intervening assessment of other SPs. These findings were compared to the assessment of two experts, who also measured the size of the CTM, distance from suprasternal notch to centre of the CTM, and whether skin markings over the CTM still overlay it after movement of the neck (and return to the same eFONA position). The operator’s confidence and time time for each assessment was also recored. A power calculation showed us that we required 35 assessments for each technique. We recruited 12 SPs, each being assessed with all techniques by three anaesthetists and three medical students. Therefore, the study number targetted 36 data points for each technique performed by each group of operators (and 72 for each technique in total). However, due to the withdrawal of one SP, the data collected included 33 data points for each technique and 66 overall.

Ethical approval for this study was sought from the University of St Andrews Teaching & Research Ethics Committee.

*12 participants were recruited, one withdrew at the start of data collection (therefore the remaining 11 were assessed)
Trial website
Trial related presentations / publications
Public notes

Contacts
Principal investigator
Name 95294 0
Dr James Bowness
Address 95294 0
Department of Anaesthesia
Level 6, Ninewells Hospital
James Arrott Drive
Dundee
DD1 9SY
Country 95294 0
United Kingdom
Phone 95294 0
+44 1382 632 175
Fax 95294 0
Email 95294 0
james.bowness@nhs.net
Contact person for public queries
Name 95295 0
Dr James Bowness
Address 95295 0
Department of Anaesthesia
Level 6, Ninewells Hospital
James Arrott Drive
Dundee
DD1 9SY
Country 95295 0
United Kingdom
Phone 95295 0
+44 1382 632 175
Fax 95295 0
Email 95295 0
james.bowness@nhs.net
Contact person for scientific queries
Name 95296 0
Dr James Bowness
Address 95296 0
Department of Anaesthesia
Level 6, Ninewells Hospital
James Arrott Drive
Dundee
DD1 9SY
Country 95296 0
United Kingdom
Phone 95296 0
+44 1382 632 175
Fax 95296 0
Email 95296 0
james.bowness@nhs.net

Data sharing statement
Will individual participant data (IPD) for this trial be available (including data dictionaries)?
No
No/undecided IPD sharing reason/comment
Only pooled data will be available as this is relevant to the overall success of each technique.
What supporting documents are/will be available?
Study protocol
Statistical analysis plan
Ethical approval
How or where can supporting documents be obtained?
Type [1] 3549 0
Study protocol
Citation [1] 3549 0
Link [1] 3549 0
Email [1] 3549 0
james.bowness@nhs.net
Other [1] 3549 0
The statistical analysis plan is available within the attached protocol.
Type [2] 3550 0
Ethical approval
Citation [2] 3550 0
Link [2] 3550 0
Email [2] 3550 0
james.bowness@nhs.net
Other [2] 3550 0
Summary results
Have study results been published in a peer-reviewed journal?
No
Other publications
Have study results been made publicly available in another format?
Yes
Other publication details
Citation type [1] 4205 0
Conference abstract
Citation/DOI/link/details [1] 4205 0
This abstract has been submitted for presentation at the World Airway Management Meeting (Amsterdam, November 2019). It is currently under review.
Results – basic reporting
Results – plain English summary
BACKGROUND INFORMATION
When patients undergo general anaesthesia, it is vital that the anaesthetist is able to oxygenate them by providing ventilation through their airway. Rarely, this is not possible, and the final step in this process of managing this clinical emergency is to gain access to the trachea via the front of the neck, via the cricothyroid membrane (CTM). We compared the accuracy, confidence and speed of techniques to identify the CTM, and whether skin markings remained over the CTM after moving the neck.

PARTICIPANT CHARACTERISTICS
Operators: three anaesthetists (mean age 33 years, range 30-34 years) and three medical students (mean age 21 years, range 20 - 23 years).
Simulated Patients (SPs): 11 female SPs, mean age 70 years (range 53 - 81 years) with mean BMI 25.6 kg/m2 (range 20 - 32 kg/m2).

KEY RESULTS
The highest accuracy (84.9%) was achieved by anaesthetists using ultrasound, but there was no statistically significant difference in accuracy of any method overall. Operators were significantly more confident using ultrasound compared to palpation, but took significantly longer. Experienced operators were significantly quicker and more confident, but no more accurate. Skin markings remained over the CTM after time and changing position of the neck when.

LIMITATIONS
No SPs assessed had any known pathology of the front of the neck and all were of near normal BMI (mean 25.57 kg/m2), so care must be taken when extrapolating these results to other patients.