Background

Out-of-hospital cardiac arrest (OHCA) is a critical incident with a high mortality rate.1 For non-traumatic cardiac arrest (CA) the most frequent aetiology is cardiac disease,2 3 with deaths related to failure to achieve return of spontaneous circulation (ROSC), circulatory failure after ROSC or anoxic brain damage.4 During cardiopulmonary resuscitation (CPR), the cardiac output is usually not sufficient to maintain consciousness and the lack of oxygen delivery can result in irreversible damage to vital organs.1 Augmentation of the circulation and hence oxygen delivery to vital organs such as the brain and heart during CPR is therefore beneficial.

Balloon occlusion of the aorta was introduced in the Korean War in 1954 as a means to stabilise soldiers with intraabdominal haemorrhages.5 After this, resuscitative endovascular balloon occlusion of the aorta (REBOA) has been employed in patients in haemorrhagic shock or CA secondary to trauma. Continuous occlusion of the aorta with REBOA gives a redistribution of cardiac output to the organs proximal to the occlusion including the brain and heart6 (figure 1).

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Figure 1

Aortic zone I occlusion.

Several animal studies demonstrate that REBOA during CPR increase both coronary artery blood flow and coronary perfusion pressure and increase the rates of ROSC.7–14 Aortic occlusion during CPR also gives clinically relevant increased carotid artery blood flow,10 15 cerebral arterial blood flow8 9 15–17 and cerebral perfusion pressure.8 9 15 18 Based on these preclinical data, patients in non-traumatic CA might benefit from REBOA in the thoracic level during CPR.

There are no systematic human studies on the use of REBOA for non-traumatic CA. To our knowledge, only three case reports are published, of which two patients were considered to have a positive effect of REBOA.19–21 One explanation for that REBOA is not introduced for OHCA is the feasibility of REBOA insertion in the prehospital setting. However, technological advances in the REBOA technique now allows for fluoroscopy-free aortic occlusion22 and REBOA is at present used by numerous prehospital services, both civilian and military on trauma patients.23

The Norwegian physician staffed prehospital emergency medical services (P-EMS) include anaesthesiologists.24 These physicians will regularly be part of the resuscitation team at OHCA. All anaesthesiologists are skilled in establishing central vascular lines using the Seldinger technique and the use of ultrasound. However, the implementation of a new procedure such as REBOA requires special training before implemented in clinical practice. An educational programme was therefore designed to educate, train and implement the REBOA technique to prehospital personnel. In this report, we describe the organisation of a team-based REBOA training programme and the evaluation of REBOA competencies in a high-fidelity simulation scenario, in preparation for a clinical feasibility study on REBOA in OHCA.

Methods

Part 4: high-fidelity simulation

This part was held in the Centre for Medical Simulation, St. Olavs Hospital. The facility simulated a prehospital setting and was equipped with sound recording and video recording and a one-way mirror window. Video sequences were used in the debriefing session.

The scenario started with establishing advanced cardiovascular life support (ACLS) according to current guidelines from The Norwegian Resuscitation Council.30 Ambulance personnel and/or medical students trained in ACLS participated, which is representative of the personnel resources usually available at scene. After endotracheal intubation, establishing manual chest compression and intravenous access on the upper body, the decision to insert a REBOA catheter was made. The resuscitation mannequin used (Resusci Anne First Aid, Laerdal Medical, Norway) is not designed for use of a mechanically chest compression machine; therefore, only manual chest compressions were performed (figure 2). The ultrasound-guided femoral artery access was performed on the designed cannulation block, integrated into the resuscitation mannequin.

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Figure 2

High-fidelity simulation with REBOA application during ACLS. ACLS, advanced cardiovascular life support; REBOA, resuscitative endovascular balloon occlusion of the aorta.

All teams where given the same case; a 59-year-old man with known hypertension, monotherapy antihypertensive treatment, suffering from a CA at his home, wife present and by-stander CPR of good quality until the ambulance crew arrived. Initial rhythm was ventricular fibrillation (VF) and this VF was refractory regardless of other treatment than REBOA. ROSC was simulated 1 min after balloon occlusion. The scenario was aborted after the team recognised ROSC and started to prepare for departure to hospital.

Assessment of performance

Global rating scale (GRS) is an assessment tool based on different aspect of quality in operative performance, adapted from a validated scoring system.31 It is a quantitative marker of performance and is not specific to the REBOA procedure and may apply to other endovascular or technical procedures. It is shown that procedure-specific rating scales can be used to assess trainee’s competence in endovascular procedures32 or other bedside procedures.27 Since a GRS for a prehospital REBOA procedure does not exist, an objective structured assessment of prehospital REBOA application (OSAPRA) chart, modified for the REBOA procedure, was developed (figure 3). The OSAPRA consist of 12 5-point categorical scores each anchored 0–4. Cut scores for adequate performance had to be determined without previous empirical data. Based on what was considered as the minimum level of performance, the investigators agreed on a cut score of 30 of a total of 48 points on the OSAPRA. Each assessment was performed based on video recording and done independently by two observers. If major discrepancies between the observer ratings occurred, a third observer performed an independently assessment, then the observers discussed until agreement.

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Figure 3

Objective structured assessment of prehospital REBOA application chart. REBOA, resuscitative endovascular balloon occlusion of the aorta; ROSC, return of spontaneous circulation.

Results

Time for REBOA procedure at simulation

The time needed to perform the REBOA procedure was 8.5 (6.3–12.7, SD 2.2) min (figure 4). The time interval started when the physician called procedural start and stopped when the balloon was inflated. The corresponding time from arrival at scene to balloon inflation was 12.0 (8.8–15, SD 2.1) min.

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Figure 4

Time (minutes) used to perform the procedure for the seven candidates.

Competency assessment of REBOA procedure in simulation

The total objective assessment scores of the candidates’ competency was 41.8 (39–43.5, SD 1.4) points out of 48 (figure 5). All scores are mean values from the two observers. No major discrepancies in grading of the candidates occurred between the observers.

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Figure 5

OSAPRA scores for the seven candidates. OSAPRA, objective structured assessment of prehospital REBOA applica+tion.

Discussion

This study showed that a team based four-step educational programme resulted in adequate performance of a REBOA procedure in a simulated OHCA setting.

This educational programme’s stepwise combination of theory, training on mannequins and patients and the use of high-fidelity simulation provides the trainees with adequate competency in a simulated model. The time needed to establish a REBOA catheter was ~8.5 min. Based on the feedback from the participants and the observers, we observed that the procedure did not interfere with the quality of the ACLS given simultaneously. This indicates that the procedure does not add significant time to the prehospital resuscitation time and will not interact negatively on established care.

The use of ultrasound is mandatory. A landmark-oriented approach to femoral arterial cannulation is difficult in patients with low blood pressure or no palpable femoral pulse, which is the case in 40% of patients receiving CPR.35 Ultrasound guidance for femoral artery catheterisation is associated with 49% reduction in overall complications and increases the likelihood of first-attempt success.36 Several studies describes how to measure or predict the length from the common femoral arterial puncture site to zone I.37–39 Detailed calculations, regardless of simple input parameters, are not likely to be performed in a prehospital setting. Based on the experiences from the catheterisation lab at St. Olavs Hospital, we used a fixed length of guidewire and balloon catheter placement. The placement was also controlled with a present pulse in the left radial artery suggesting balloon inflation below the left subclavian artery. The descending aorta is ~25 mm in width in the age span of patients eligible for inclusion.40 41 To minimise the risk of complications such as aortic rupture22 or local complications, 7 Fr equipment and a 20 mm balloon is used. Hence, some patients will potentially have subtotal aortic occlusion. Given an occlusion length of 30 mm, the great increase in resistance to blood flow will provide the same haemodynamic effect and limit the risk of aortic injury. Thus, for REBOA done in the prehospital setting, there must be a consideration for partial aortic occlusions versus to avoid risk of aortic injury.

An objective measurement of skills is difficult. Checklists are easy to use, but to evaluate clinical skills, studies suggest that GRS is a more dependable measure.27 42–44 Cut scores are often used to assess performance and the selection of a cut score risk to be biased by evaluators opinions. There are recommendations for how to decide cut scores or define adequate performance.45–47 However, a GRS for a prehospital REBOA procedure does not exist and cut scores to the OSAPRA score had to be determined without previous empirical data. A possible method to set the cut score is the Angoff method,48 in which a group of experts establishes the cut score based on a fictitious ‘borderline’ candidate. Experts present a description of a performance that they believe is on the borderline between competent and incompetent, and the cut score is set based on the score of this performance. Borderline cases can also be identified by that the raters record ‘red flag’ performances, using a global impression. The reasons to identify a red flag performance for interventional procedures are often significant breaches of sterility or performances leading to damage to important structures or organs.27 We believe that a combination of cut scores and an overall global impression on safety and competence can be used as foundation to deem adequate competency.

Practice in an interventional radiology lab can be difficult to perform in places that lack this service or where hospital or interdepartment regulations are strict. We propose that the REBOA procedure then may be learnt at specialised courses with a structured educational programme, for instance, like the one described here.

Applying high-fidelity simulation to an educational programme provides a powerful platform for evaluating technical skills as well as team work and communication. In addition to the actual training, we consider the debriefing sessions as important for the learning effect. The debriefers role in the debriefing session is important and difficult, and the learning effect of such a session is dependent of the skills and learning environment created by the debriefer.33 One of the investigators works at the Centre for Medical Simulation and is trained as a facilitator in debriefing sessions. The debriefers are known to the trainees. We believe that this contributed positively to create a non-hostile debriefing environment.

It must be recognised that REBOA placement will not always be successful. Therefore, a part of the training must be to abort the procedure if difficult or if it interferes with performance of standard CPR. There will also be operational circumstances such as cold weather or environmental hazard where REBOA should not be initiated. This study does not answer how REBOA can be achieved during real-life field operations. Moreover, the frequency of REBOA complications can be different in a prehospital setting and clinical studies are needed to observe if REBOA is feasible in a prehospital setting during CA and if complications associated with REBOA balance the potential benefit from REBOA. We also emphasise that the concept of REBOA during CA is in its infancy and several issues related to what is the better technique must be developed.

We recognise that this study has some limitations. First, it is a single-centre study, and only assessed seven physicians and three paramedics. Second, we included only anesthesiologists working in a P-EMS system with a homogenous set of skills and the results might therefore not be generalised to physicians from other specialties. However, the study is relevant to services such as in Scandinavia, where mainly anesthesiologists participates in the physician-manned P-EMS. Third, the simulation was done on mannequins, and although the high-fidelity simulation mimicked the prehospital setting, it may not translate directly to the real prehospital environment. Fourth, this is a scenario where all participants are prepared specifically for testing the REBOA procedure and where all participants knew the indications well. Finally, the objective assessment chart had to be developed for this study, meaning that it has yet to be validated.

Strengths of this study is that it is specifically designed for a team competent in the Seldinger technique, thereby relevant for the personnel who will perform REBOA in real-life settings. We evaluated both technical and communication skills, as well as team work. The OSAPRA scoring chart is constructed in a systematic manner, based on input from physicians with a wide range of expertise.

REBOA may be an important modality for out-of-hospital ACLS. This is supported by animal studies on physiology during CPR. However, it is not known if REBOA will give benefit on human ACLS. An answer to this question can only be given by a comparative study of REBOA plus standard care versus standard care alone. However, it is reasonable to develop and perform an educational programme and to test in-field feasibility of REBOA in the prehospital setting before initiating a comparative study. This clinical feasibility study is currently in progress.

Conclusions

This four-step approach to educate, train and implement the REBOA technique in a prehospital working team provides adequate competence in a simulated setting. This training is a first step before the start of a planned feasibility trial of REBOA for OHCA. We recommend the use of a systematic training programme and the OSAPRA score to guide and improve training. In a simulated prehospital setting, the teams used 8.5 min to establish a REBOA catheter. This indicates that the procedure does not add significant time to the resuscitation time prehospital. Based on the feedback from the participants and the observers, we conclude that the procedure does not interfere with the quality of the ACLS given simultaneously.