Comparison of inguinal fist compression versus commercial windlass tourniquet for reduction in femoral artery blood flow by untrained providers: a protocol for a superiority, assessor-blinded, cross-over, randomised controlled trial

Abstract

Introduction

Effective haemorrhage control is crucial in cases of limb trauma involving arterial injury, such as shark attacks, to prevent potentially fatal outcomes. International first aid consensus recommends the use of arterial tourniquets (proprietary or makeshift) as a primary treatment for life-threatening external bleeding. Manual pressure applied directly over a major artery proximal to the injury, such as inguinal fist compression (IFC), is more accessible in a first-aid situation, but is currently not recommended due to limited evidence. The purpose of this study is to determine whether the application of IFC is superior to commercial windlass tourniquets (CWTs) in reducing blood flow in the femoral artery when performed by untrained bystanders.

Methods and analysis

Stopping Haemorrhage by Application of Randomised Compression or Tourniquet (SHARC-2) is a superiority, assessor-blinded, cross-over, randomised controlled trial conducted with healthy untrained adult volunteers in non-clinical settings. Participants will be rotated as providers and recipients of both IFC and CWT, with providers randomised to the order that they perform the techniques. Providers will be exposed to an educational infographic before applying that technique to a recipient behind a drop sheet. A sonographer, blinded to the technique, will measure the peak systolic velocity of blood flow in the superficial femoral artery using Doppler ultrasound at baseline and then during application of each technique for 5 min. The mean percentage reduction in peak systolic velocity will be compared between IFC and CWT groups.

Ethics and dissemination

Ethics approval for this study was granted by the Bond University Human Research Ethics Committee (BUHREC JF01036) on 23 January 2023. All participants will be provided with written informed consent prior to enrolment and the trial will involve healthy adult volunteers. To minimise risk, preintervention screening, sonographic assessment and postintervention follow-up will be implemented with adverse events monitored and reported in accordance with HREC guidelines. Results will be disseminated through peer-reviewed journals, academic conferences, local resuscitation forums and public health education initiatives. A lay summary will also be shared with relevant community groups and via social media platforms to enhance public accessibility.

Trial registration number

ACTRN12624001054505.

STRENGTHS AND LIMITATIONS OF THIS STUDY.

• By recruiting untrained participants, this study offers a pragmatic evaluation of a bystander’s ability to effectively perform either technique.

• The utilisation of an assessor-blinded cross-over randomised controlled trial provides the highest level of evidence to date for first aid techniques to mitigate lower limb arterial blood loss.

• Both techniques are likely to produce a degree of discomfort, which may hinder providers in applying them effectively.

• The absence of visual feedback by way of reduced bleeding may affect the magnitude of force applied for both interventions.

• While the study is powered to achieve statistical significance, a study sample of 50 healthy volunteers is unlikely to be entirely representative of the general population.

Introduction

Background and rationale

Massive external haemorrhage from an arterial injury following a marine fauna encounter or shark attack can be fatal. The Surf Life Saving Australia 2023 Coastal Safety Briefing on marine fauna found that in Australia, shark attacks are responsible for an average of 2.44 deaths per year,¹ with the incidence of non-fatal encounters likely to be much higher than this.² In catastrophic exsanguination following trauma, a primary goal of prehospital medical management is to reduce blood loss to preserve organ function and reduce the need for blood product administration³. Current international first aid consensus recommends⁴ the use of a windlass tourniquet (commercial or makeshift) as a first-line treatment to control life-threatening extremity bleeding at non-compressible sites.⁵ However, there is no reference to arterial pressure point techniques, such as the inguinal fist compression (IFC) technique.

Windlass tourniquets exist in two forms: commercially manufactured windlass tourniquets (CWTs) or improvised devices created with materials in the field. Several types of CWT exist, but to date, none has been robustly evaluated against IFC in untrained bystanders. IFC is a novel technique that requires no specialised equipment to employ. The aim of this study is to investigate the efficacy of the general population, educated with an infographic, on their ability to occlude the femoral artery using two different techniques: (1) application of IFC and (2) application of a CWT.

Objectives

The primary objective of the Stopping Haemorrhage by Application of Randomised Compression or Tourniquet (SHARC-2) trial is to determine whether IFC is more efficacious than a CWT in reducing femoral artery blood flow (as percentage reduction in peak systolic velocity (PSV) at 5 min in healthy volunteers, applied by untrained adults after reading an infographic. Secondary objectives are to determine if IFC has a higher frequency of complete occlusion at 5 min, has a faster application time and is the preferred intervention by providers and recipients.

Trial design

SHARC-2 is a superiority, assessor-blinded, crossover randomised controlled trial, based on a pilot study from the same authors with a similar protocol.⁶ The protocol adheres to the Standard Protocol Items: Recommendations for Interventional Trials (SPIRIT) statement.

Methods: participants, interventions and outcomes

Study setting

Recruitment and data collection will be conducted at several venues, such as sporting clubs in Gold Coast, Queensland, Australia. The equipment required for the trial will be transported to the venue and set up in a location that maintains the privacy of the participants.

Eligibility criteria

There are three stages in ensuring eligibility is met, and safety maintained.

1. Screening: Potentially eligible participants will be approached and invited to take part in the trial by a research team member at coordinated data collection sessions. An information sheet outlining the research trial will then be provided, which will include a list of eligibility screening questions. Those who are screened and excluded will be recorded with reasons documented.

2. Review: Volunteers who satisfy initial screening will be asked to present to the nominated venue at a specified time (if not already on site). A review of complete eligibility criteria by a member of the research team will then take place. The inclusion criteria are modelled to represent an untrained adult bystander in Australia (table 1). The exclusion criteria seek to ensure participant safety by identifying medical issues that could be exacerbated by providing or receiving either IFC or CWT techniques (table 1). If eligible and written consent is obtained, the participant will proceed in the trial as a provider.

3. Assessment: Before proceeding as a recipient, participants will undergo visual inspection of their groin and lower limbs, with an emergency physician examining for pathologies outlined in table 1. A targeted sonographic assessment will then be performed to exclude vascular anomalies or undiagnosed peripheral vascular disease as outlined in table 1. If an abnormality is detected in the assessment of the lower limb, the participant will not progress as a recipient. They will be informed of the findings and be referred to their general practitioner with a letter recommending further evaluation. Given that the recruitment and data collection will take place in groups, participants may be required to be a recipient more than once (this will be documented).

Table 1. Eligibility criteria.

Inclusion criteria	Exclusion criteria (provider)	Exclusion criteria (recipient)
Aged between 18 and 59 years (inclusive) English language fluency (including as a second language) No formal medical training beyond first-aid No training in arterial tourniquet application	Diagnosis, or evidence of, conditions that could potentially be exacerbated by participation as a provider: Musculoskeletal eg, carpal tunnel syndrome, previous shoulder dislocation or surgery (eg, reconstruction), recent injury	Diagnosis, or evidence of, conditions that could potentially be exacerbated by participation as a recipient Musculoskeletal for example, previous groin surgery (eg, hernia repair, hip replacement), recent injury. Vascular eg,arterial venous malformation or aneurysmal disease of the femoral artery; peripheral vascular disease, including PSV of the SFA outside the normal reference range15 Neurological eg,peripheral nerve disease Haematological eg, hypercoagulability, coagulopathy or anticoagulation Dermatological, for example, severe dermatitis, infection or sunburn

PSV, peak systolic velocity; SFA, superficial femoral artery.

Who will take informed consent

Once volunteers are deemed eligible for the trial, a member of the research team will check their understanding of their involvement in the trial, based on the written information provided. Written consent will then be obtained from the volunteer willing to participate in the trial.

Additional consent provisions for collection and use of participant data and biological specimens

There are no provisions for future ancillary studies using the data collected in this trial.

Interventions

Explanation for the choice of comparators

Current international guidelines on first aid management of major limb haemorrhage at non-compressible sites include the use of arterial tourniquets applied by trained personnel.⁵ However, this relies on the availability of CWTs and trained personnel able to apply them. Emerging evidence suggests that untrained members of the community may be able to provide more effective reduction in femoral artery blood flow in healthy adult volunteers with the application of IFC compared with CWTs.6,11 While current literature has advanced the understanding of IFC, this study is designed to address its collective limitations, allowing integration into first aid guidelines. Specifically, this includes using participants with no medical training, employing assessor blinding, extending the duration of technique application and refinement of infographics. In a trauma setting, larger reductions in femoral artery blood flow would lead to lower volumes of blood loss and better patient outcomes. Given the time-critical nature of extremity arterial haemorrhage, IFC could be rapidly provided as first aid by bystanders while awaiting the attendance of emergency services.

Intervention description

Inguinal fist compression

The provider will place the fist of their dominant hand at the midpoint of the recipient’s inguinal canal, midway between the anterior superior iliac spine and the pubic symphysis (figure 1). The leg used (left or right) for each data collection session will be determined by the ergonomics of each testing space and will be recorded. Maximal pressure, as tolerated by the recipient, will then be applied over the compression point as per the technique reported by Taylor and Lamond.¹⁰

Figure 1. Inguinal fist compression technique.

Commercially manufactured windlass tourniquet

The CWT used will be the Combat Application Tourniquet manufactured by C-A-T Resources (figure 2). The provider will apply the CWT to the upper thigh of the recipient and the windlass rotated to and locked at the maximum tolerable tightness for the recipient. Application of the CWT will be over clothing to emulate real-world utilisation.

Figure 2. Combat application tourniquet.

Infographics

Separate infographics were developed for the IFC and CWT which outline step-by-step instructions on the application of each intervention (figures3 4). The IFC infographic was adapted from that used in the study conducted by Taylor and Lamond.¹⁰ The CWT infographic was adapted from the manufacturer’s instructions.¹² Both infographics were tested in an initial pilot study and further developed with input from a consumer advisory group with members of the general population.

Figure 3. IFC infographic.

Figure 4. CWT infographic.

Criteria for discontinuing or modifying allocated interventions

Should the recipient verbally indicate at any stage that the intervention being applied is not tolerated, the provider will immediately release it. A member of the research team will also intervene to release the intervention if they deem that the recipient is experiencing excessive pain.

Strategies to improve adherence to interventions

The infographics used in this trial are modified versions of those used in the pilot study. Feedback from the Gold Coast Hospital and Health Service Consumer Advisor Group has been used to enhance the readability of both infographics for this study. From the participant’s perspective, the researcher team will ensure that participants are aware that both interventions have the potential for discomfort.

Relevant concomitant care permitted or prohibited during the trial

No other concomitant intervention or treatment that may alter femoral artery blood flow in the recipient is permitted during data collection.

Provisions for post-trial care

Recipients will be evaluated by an emergency physician following both interventions for complications and to assess the return of normal superficial femoral artery (SFA) blood flow, both clinically and using Doppler ultrasound, immediately after their participation. Although no participants from the pilot study encountered any adverse event or complication, further medical evaluation will be arranged at a local hospital for any participant who requires it. All participants will be provided with a standardised letter outlining their involvement in the study should they need it for medical purposes as well as the contact details of the principal investigator. Participants will be made aware that they may experience localised bruising or mild pain following their involvement in the study, but anything beyond this will likely require further medical evaluation. Study volunteers will also be telephoned, text messaged or emailed by the research team within 48 hours to assess for any complications or adverse outcomes.

Outcomes

The trial’s primary outcome is the reduction in PSV of the SFA at 5 min post application of the intervention (IFC or CWT), expressed as a percentage. This was chosen as it determines the efficacy of the intervention for reduction in blood flow, that the provider has sustained for a reasonable period as a first-aid measure. A qualified sonographer will perform Doppler ultrasound of the SFA blinded to the intervention.

Secondary outcomes will include:

• Time to apply intervention: recorded as time from infographic exposure until application of intervention, as indicated by the provider. A member of the research team will use a stopwatch to record this duration in seconds.

• Blood flow reduction: PSV measurements will be taken at baseline (pre-intervention), immediately post application of the intervention (0 min), and at 1 min intervals until 5 min (ie, 1, 2, 3, 4, 5 min).

• Complete occlusion: the proportion of recipients with complete occlusion of blood flow (ie, PSV=0cm/s) at 5 min will be compared between interventions. The duration of complete occlusion (number of PSV measurements with complete occlusion) will also be compared.

• Effect of provider characteristics, including age, biological sex, gender, first-aid training, level of education, English as second language and grip strength (measured by dynamometer), on the primary outcome of percentage PSV reduction at 5 min.

• Effect of recipient characteristics, including age, biological sex, gender, clothing type and mid-thigh circumference, on the primary outcome of percentage PSV reduction at 5 min.

• Provider reported:

  • Level of difficulty of applying the intervention, rated on a Likert scale from 0 to 10 (0=no difficulty, 5 moderate difficulty, 10 most difficult).

  • Ability to sustain the application of the intervention, rated on a Likert scale from 0 to 10 (0=very easy to 10=very difficult).

  • Preference for technique (0=IFC preferred, 5=equal/no preference for technique, 10=CWT preferred).

These will all be manually recorded by the provider on a data sheet after they provided both interventions.

• Recipient reported:

  • Maximal level of discomfort for applied technique, rated on a Likert scale from 0 to 10 (0=no discomfort, 5=moderate discomfort, 10=extreme discomfort).

  • A preference for technique received, rated on a Likert scale from 0 to 10 (0=IFC preferred, 5=equal/no preference for technique, 10=CWT preferred).

These will all be manually recorded by the recipient on a data sheet after they have received both interventions.

• Any adverse outcomes from the intervention, with recipients asked immediately afterwards and at follow-up within 48 hours by phone call, text message or email. Participants will also have the contact details of the lead author to report any adverse events.

Participant timeline

As outlined in figure 5, the maximum time requirement for each participant is anticipated to be 57 min. The first participant for each group will not be required for steps 4, 5 and 6. The last participant of each group will not be required for steps 7 and 8.

Figure 5. Individual participant timeline, the first participant in each group will skip steps 4, 5 and 6.

Sample size

This trial’s sample size calculation was informed by the previous pilot study.⁶ Sample size calculations were based on a superiority hypothesis of IFC compared with CWT with a primary outcome of PSV at 5 min post application of the intervention. Using the software G*Power and the pilot study mean difference of 40.0% and SD of difference of 61.1%, with power 0.9 and significance level 0.05, a minimum sample size of 30 participants was calculated, which will provide 60 primary outcome data points (30 per intervention). This sample size also achieves power above 80% for the key secondary outcome of proportion of participants achieving complete occlusion, based on pilot study data of 87.5% with IFC and 50% with CWT. To allow for any withdrawals or technical issues precluding primary outcome data collection, the goal will be for up to 40 participants to be recruited with 80 primary outcome data points, that is, 40 applications of each intervention (IFC and CWT).

Recruitment

To ensure adequate recruitment to the trial, volunteers will be sought out from venues in the Gold Coast city region of South-East Queensland, Australia. This could include sporting groups, Surf Life Saving clubs, universities or other community groups. Organisation gatekeepers will be given participant information sheets, which outline all relevant details such as allocated time commitment for participants. Where possible, a member of the research team will conduct pre-screening of participants remotely via phone or email, to ensure efficiency for the scheduled data collection sessions. Data collection will either occur in those community venues or centrally at a designated room at Bond University.

Assignment of interventions: allocation

Sequence generation

The order of the interventions performed by each provider will be dictated by the web-based Griffith Randomisation Service.¹³ This is a centralised, computer-generated algorithm with randomisation.

Concealment mechanism

Described in ‘Sequence generation’ section.

Implementation

After consenting, eligible participants will be enrolled into the trial by a member of the research team who will then allocate the order that the interventions will be applied, as determined by the Griffith Randomisation Service.

Assignment of interventions: blinding

Who will be blinded

The trial will be conducted as an assessor-blinded study, with participants unavoidably aware of the intervention. The sonographer performing the PSV measurements will be blinded to the intervention using a drop sheet to visually conceal the intervention (figure 6 a and b) and noise cancelling headphones to audibly mask any dialogue or sounds that might reveal the intervention. To enhance blinding of the intervention, the provider will remain beside the recipient during data collection, regardless of intervention. The statistician will also be blinded to the intervention when analysing the primary and secondary outcomes.

Figure 6. a and b: Orientation of equipment and key personnel.

Procedure for unblinding if needed

Unblinding will not be required in this trial. The drop sheet will maintain blinding even when the intervention is released, and the return of arterial blood flow is checked by the sonographer.

Data collection and management

Plans for assessment and collection of outcomes

Participant role progression

Participants will progress from being a provider to being a recipient before exiting the testing area (table 2). The exception to this is the participant who acts as the initial recipient (participant 1) as they are no longer naive to the interventions. As the provider, participants will provide both techniques with a 5 min wash-out period in between (figure 7). Participants may be required to be a recipient more than once, depending on the group requirements, but will only act as a provider once.

Table 2. Transition of participants as provider or recipient per session.

Episode	1	2	3	4	5
Provider	Participant 2	Participant 3	Participant 4	Participant 5	Participant 6
Recipient	Participant 1	Participant 2	Participant 3	Participant 4	Participant 5

Figure 7. Schematic diagram of data collection. PSV, peak systolic velocity.

Baseline data collection

All participants will have baseline data collected prior to randomisation, as listed in box 1. When acting as a recipient, a baseline measurement of the SFA PSV will be taken by a qualified sonographer using a high-frequency linear transducer. This measurement will be taken at the distal SFA, with the location marked on each participant to ensure reliability for subsequent readings and assist efficiency of timing.

Box 1. Participant data.

Age.

Biological sex.

Gender.

Native language/s.

Occupation.

Level of education.

Arm dominance.

Coastal activities.

Height.

BMI.

Thigh circumference.

Grip strength.

BMI, body mass index.

Trial data collection

After the provider is exposed to the first infographic (T0), they then apply the technique and indicate when this is completed (T1). At this point, the sonographer immediately records the PSV, repeating this at 1 (T2), 2 (T3), 3 (T4), 4 (T5), 5 min (T6). Three measurements are taken for each time point with the median value used. A researcher will record times from a digital stopwatch and indicate minutely time points for the sonographer to take measurements. Once all PSV values are recorded and the intervention is released, the sonographer checks that normal blood flow has returned, and the above steps are repeated for the second intervention. Following this, the recipient leaves the testing area, the provider transitions to become the recipient and a new participant enters the testing area to act as the provider. This cycle is repeated until the end of the data collection session (box 1).

Data will be recorded onto a paper-based clinical research form (CRF) by a member of the research team. Following the data collection session, all CRF data will be entered into an Excel spreadsheet.

Plans to promote participant retention and complete follow-up

The time commitment from participants will be less than 60 min (figure 5) for the majority of which they will be engaged in a physical task, thus increasing the likelihood of retention. Once commenced, outcome measures will be collected as per the SPIRIT timeline (online supplemental appendix C).

Any adverse events will be recorded at the end of the data collection session, with follow-up contact made within 48 hours to document any further adverse events and as a safety feature.

Data management

All data will be treated in accordance with Bond University’s Research Data Management and Sharing Policy.¹⁴ Data will be initially recorded on CRFs which will then be scanned with original physical copies destroyed. The remaining digital data will be stored in Microsoft SharePoint for the mandatory data retention period of 5 years.

Confidentiality

No individual data will be reported in this trial.

Plans for collection, laboratory evaluation and storage of biological specimens for genetic or molecular analysis in this trial/future use

This study does not involve the collection of biological specimens.

Statistical methods

Statistical methods for primary and secondary outcomes

Continuous data will be summarised as mean (SD), or median (IQR) and categorical data will be summarised as frequency (percentage). Differences between interventions in continuous outcomes, including the primary outcome of percentage reduction in PSV, will be analysed using paired t-tests, or the Wilcoxon signed rank test if normality assumptions are violated. The primary outcome will be tested for superiority of the IFC intervention. The null hypothesis of no difference in PSV reduction between interventions will be rejected if the p value for this outcome is less than 0.05. Additional testing for period or carryover effects will be performed using analysis of variance. The effect of provider and recipient factors on the primary outcome will be assessed using a mixed-effects model, with the parameter of interest included as a fixed effect. Significance testing for categorical outcomes will be performed using Fisher’s exact test. All data will be analysed using Stata V.14.2 or later. Further details can be found in the Statistical Analysis Plan (online supplemental appendix B).

Interim analyses

There is no requirement to perform an interim analysis or have stopping guidelines for this trial.

Methods for additional analyses (eg, subgroup analyses)

Subgroup analyses will be performed on the baseline data outlined in box 1, provided there are adequate data.

Methods in analysis to handle protocol non-adherence and any statistical methods to handle missing data

The primary analysis will be conducted on an intention-to-treat basis. Thus, outcomes collected for each episode at 5 min post application of the intervention will be compared according to the randomly allocated order of intervention, regardless of the actual performance of this intervention by the provider. For the primary analysis, recipients who did not have primary outcome data recorded at the 5 min time point (eg, due to inability to tolerate the intervention) will have the missing outcome data imputed as the last recorded observation for that recipient, under the principle of including data from all randomised participants in an intention-to-treat analysis. A sensitivity analysis will be conducted using the per-protocol population, constituting only recipients with primary outcome data available at the 5 min time point.

Plans to give access to the full protocol, participant-level data and statistical code

Deidentified data associated with the trial will be available on reasonable request.

Oversight and monitoring

Composition of the coordinating centre and trial steering committee

This trial will be coordinated by clinicians working at major trauma centres in Australia (Gold Coast University Hospital and The Canberra Hospital) and academics from the Water Based Research Unit at Bond University, Robina, Australia. The Trial Steering Committee will be composed of academics, emergency physicians and a trauma surgeon, who will provide oversight and will regularly meet during trial recruitment.

Composition of the data monitoring committee, its role and reporting structure

The Research Governance Officer at Bond University will monitor the conduct of the research trial, ensuring that the trial is conducted according to protocol and that data are collected appropriately.

Adverse event reporting and harms

Participants will be assessed for adverse events resulting from their involvement in the trial at the end of data collection episodes and within 48 hours of completion. All adverse events and any other unintended effects of the trial interventions will be recorded, and the principal investigator will report any serious events to the institutional Human Research Ethics Committee (HREC) within 72 hours of notice.

Participants who have abnormalities detected on screening assessment will be provided with a letter for their general practitioner informing them of the finding and advising further assessment and management.

Frequency and plans for auditing trial conduct

Annual progress reports will be submitted to the Research Governance Officer and the HREC committee while the project is active, and a final report will be submitted on trial completion. This will include the trial status, adverse events, complaints and any protocol deviations.

Plans for communicating important protocol amendments to relevant parties (eg, trial participants, ethical committees)

Any research protocol amendments will be submitted to the institutional HREC for approval before implementation. If approved, changes to the protocol will be disseminated to the research group.

Discussion

Based on a recent pilot study with a similar protocol, there is the potential that IFC will achieve a greater reduction in femoral blood flow than CWT when applied by untrained bystanders after brief infographic exposure. Complete occlusion of the femoral artery with IFC may also be achieved more frequently and be faster and easier to apply than CWT. Reducing blood loss is a cornerstone of trauma care and has been shown to improve patient outcomes.³ Thus, implementing an intervention that can be easily taught and does not require equipment has the potential to reduce the disease burden of traumas such as shark attacks. If IFC is found to be superior to CWT, the findings will play a significant role in shaping future guidelines for first aid management of massive arterial haemorrhage from lower limb trauma in the civilian, industrial and military spaces.

Trial status

The current protocol is version 1.0 dated 11 July 2024, being the final version approved by the HREC and prior to the first participant recruited to the trial. Participant recruitment is anticipated to commence mid 2024 and be completed within 12–18 months.

The funding body had no role in the study design, recruitment, data collection, analysis and interpretation of data, writing of the report or decision to submit the report for publication.