Providing the best chest compression quality: Standard CPR versus chest compressions only in a bystander resuscitation model

Aim of the study Bystander-initiated basic life support (BLS) for the treatment of prehospital cardiac arrest increases survival but is frequently not performed due to fear and a lack of knowledge. A simple flowchart can improve motivation and the quality of performance. Furthermore, guidelines do recommend a chest compression (CC)-only algorithm for dispatcher-assisted bystander resuscitation, which may lead to increased fatigue and a loss of compression depth. Consequently, we wanted to test the hypothesis that CCs are more correctly delivered in a flowchart-assisted standard resuscitation algorithm than in a CC-only algorithm. Methods With the use of a manikin model, 84 laypersons were randomized to perform either flowchart-assisted standard resuscitation or CC-only resuscitation for 5min. The primary outcome was the total number of CCs. Results The total number of correct CCs did not significantly differ between the CC-only group and the standard group (63 [±81] vs. 79 [±86]; p = 0.394; 95% CI of difference: 21–53). The total hand-off time was significantly lower in the CC-only group than in the standard BLS group. The relative number of correct CCs (the fraction of the total number of CCs achieving 5-6cm) and the level of exhaustion after BLS did not significantly differ between the groups. Conclusion Standard BLS did not lead to an increase in correctly delivered CCs compared to CC-only resuscitation and exhibited significantly more hand-off time. The low rate of CCs in both groups indicates the need for an increased focus on performance during BLS training.

of the algorithm (compression--only dispatcher--assisted bystander CPR) led to a 22% increase in survival--to-hospital discharge. A recently published trial of the research group could demonstrate that the presence of a flowchart has a positive effect on the quality of BLS while at the same time increasing the rescuers' confidence. Nonetheless, performing CPR is exhausting. Previous publications have emphasized increasing fatigue with the duration of CPR efforts in both, standard and chest compressions--only CPR. Consequently, we wanted to test the hypothesis that chest compressions (CC) are delivered more correctly regarding the depth when utilizing the standard BLS algorithm with the aid of a flowchart as compared to the CC only algorithm utilizing an adapted CPR flowchart in a manikin resuscitation model.

Methods:
After consent of the Research Ethics Board of Medical University of Vienna and obtaining written informed consent of the participants, 84 medically untrained laypersons will be randomised to perform flow--chart assisted CPR for 300s following standard CPR guidelines or CC only CPR. The primary outcome parameter will be the total number of CC achieving the correct depth of 50--60mm. Secondary outcome parameters will be hands--off time, the total number of CC, and the compression rate. The total number of delivered rescue breaths, tidal volume, and time to deliver these will also be evaluated. Furthermore, the subjective point of exhaustion affecting the CPR quality, the reason for discontinuation of CPR if stopped within the 300sec. period and the exhaustion at the end of the CPR measures will be evaluated.

Background:
Since the introduction of the modern Basic Life Support (BLS) in the 1950, on--going efforts have been made to improve the quality of first aid measures [Handley et al. 2005, Koster et al. 2010. International BLS algorithms have been designed, validated and published to meliorate the outcome after a cardiac arrest [Koster et al. 2010].
In many European countries cardiac arrest and sudden death due to coronary ischaemia is the primary single cause of death in adults. Across Europe, with a total population of approx. 830 Million inhabitants, emergency medical service treated cardiac arrest occurs in a range of 17--53/1000,000/year [Gräsner et al. 2013].
Many of these victims of sudden cardiac arrest could survive if bystanders would act immediately while shock-able heart rhythms are still present, but successful resuscitation is unlikely once the rhythm has deteriorated to asystole [Valenzuela et al. 1998].
Chances of survival from witnessed ventricular fibrillation decreases by 7--10% every minute without cardiopulmonary resuscitation (CPR) [Valenzuela et al. 1998]. In urban areas, the Emergency Medical Services response interval is eight minutes or more [vanAlemAP at al. 2003]. Overall, bystander CPR doubles or triples survival from witnessed cardiac arrest [Wissenberg et al. 2013].
In most cases the fundament of a functional chain of survival is lay people who may or may not have been trained in BLS courses. Especially as more than two thirds of the sudden cardiac arrests are witnessed by bystanders [Müller at al. 2006]. Unfortunately, the frequency of initiating CPR by lay people is still seen to be very low. Reasons for this fact are among others, fear of making mistakes and thus harming the collapsed or reluctance to perform mouth--to--mouth ventilation [Swor et al. 2006, Svastano et al. 2011.
Evidence shows that skill acquisition and retention is, besides regular application of the algorithm, added by the simplification of BLS sequence [Koster et al. 2010]. In the process of improving the resuscitation guidelines it was one of the aims of the European Resuscitation Council to simplify the BLS algorithm and design a sequence that would be easy to remember and apply. A recently published trial of the research group could demonstrate that the presence of a flowchart has an additional positive effect on the quality of BLS [Rössler et al. 2013].

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A meta--analysis of three previously conducted trials could demonstrate that a simplification of the algorithm (compression--only dispatcher--assisted bystander CPR) led to a 22% increase in survival--to--hospital discharge [Hüpfl et al. 2010]. These findings were so convincing that they found representation in a scientific statement of the AHA regarding pre--arrival instruction by the dispatcher [Lerner et al. 2012].
Nonetheless, even when bystanders commence CPR, publications have demonstrated fatigue in both, standard and chest compressions--only CPR [Heidenreich et al. 2012, McDonald et al. 2013. Despite the fact that chest compressions--only CPR lead to an increase in total number of delivered chest compressions (CC), the fraction of effective CC (reaching the recommended depth) declines among elderlies with the longer duration of CPR [Heidenreich et al. 2012]. Noteworthy, in a publication by McDonald and colleagues, fatigue did not affect the rate of compressions. Nevertheless, the compression depth was affected from the second minute onwards [McDonald et al. 2013] This fact is of clinical relevance since for every 5mm increase in compression depth in out of hospital cardiac arrests, the odds of survival and survival with a functional outcome increase [Vadeboncoeur et al. 2014]. Even though the optimal depth remains disputed, the current ERC Guidelines recommend a depth of 50--60mm [Koster et al. 2010]. Furthermore, and a depth of >50mm has been shown to be associated with improved outcome as well as functional neurological outcome [Vadeboncoeur et al. 2014]. Nevertheless, the optimal depth is not undisputed since contrary to previously published data, a recent publication by Stiell and colleagues identified the peak in survival at 45.6mm, below the currently recommended depth [Stiell et al. 2014].
The guidelines also recommend a CC rate of 100--120/min [Koster et al. 2010]. This is in line with recently published data indicating that the maximum rate of survival to hospital discharge can be achieved when compressing at 100--120/min [Idris et al. 2015]. An increase in CC rate over 120/min can decline the probability of return of spontaneous circulation possibly due to a concordant reduction in compression depth [Monsieurs et al. 2012, Stiell et al. 2012].
Consequently, we wanted to test the hypothesis that chest compressions are delivered more correctly regarding the depth when utilizing the standard BLS algorithm with the aid of a flowchart as compared to the CC only algorithm utilizing an adapted BLS flowchart in a manikin resuscitation model.

Study Design
The investigation will be conducted as a prospective, randomized controlled study performed by the Department of Anaesthesia, General Intensive Care and Pain Management, Medical University of Vienna, Austria, according to the Good Scientific Practise guidelines of the Medical University of Vienna. The data collection will be conducted in cooperation with the Training Centre of St. John Ambulance, Vienna, Austria.

Study Population
Eligible are all volunteers of ≥18 years of age of non--medical profession, irrespective of gender. Exclusion criteria are professional medical training (nurses, medical doctors, physiotherapists, ergotherepeuts, emergency medical technician or equivalent), pregnancy (as by verbal response at the time of recruitment), and parallel participation in a clinical trial, or physical impairment or illness prohibiting physical effort.

Withdrawal and replacement of subjects
Subjects must be withdrawn under the following circumstances: --at their own request --if the subject violates the conditions laid out in the consent form/information sheet or disregards instructions by the study personnel In all cases, the reasons why subjects are withdrawn must be recorded in detail in the case report form.
Should the study be discontinued prematurely, all study materials (completed, partially completed and empty case report forms) will be retained.
Subjects who do not complete the study according to protocol will be replaced. The data from the replaced subjects will be eligible for analysis of the conducted trial periods and for safety variables.

Sample Size
In order to detect a clinically important difference of 20% in compression depth with a power of 0.8 and a significance level set at 0.05, the sample size calculation yielded a total needed number of participants at 74.
Since a drop out rate of approx. 10% must be expected 84 participants will be recruited. Data regarding compression depth utilizing standard CPR techniques in a manikin model (43±12mm) were provided by a previous publication and used to estimate the sample size [Rössler et al. 2013] Seite 7 von 13

Outcome parameters:
The primary outcome is total number of CC achieving the correct depth of 50--60mm in five minutes of manikin CPR. With this the authors want to test the hypothesis that chest compressions are delivered more correctly regarding the depth when utilizing the standard BLS algorithm with the aid of a flowchart as compared to the CC only algorithm utilizing an adapted BLS flowchart in a manikin resuscitation model. The secondary outcome parameter is hands--off time (HOT), which is defined as the sum of total time elapsed during the 300sec. of BLS in which no chest compressions are provided. This includes the pre--compression interval where the initial steps of BLS are performed as well as all interruptions of the CC, e.g. in order to ventilate or pause due to any other reason including exhaustion. Furthermore, the total number of CC, and the compression rate will be evaluated. The total number of delivered rescue breaths, tidal volume, and time to deliver these will also be evaluated.
Furthermore, questions regarding following points will be raised: "During CPR and without stopping your actions, please tell us "NOW" when you perceive your fatigue is affecting the quality of the life support performed", "How exhausted are you now (question raised directly after discontinuing the CPR) [McDonald et al. 2013] (Lickert Like Scale 1--10). If a participant choses to abort resuscitation attempts the open ended question "Why did you discontinue the resuscitation attempts?" will be raised.

Data management and calculations
Data will be described as absolute frequencies and percentages for categorical data and using mean and standard deviations (SD) for normally distributed data. All tests for p--values are two--sided and p≤0.05 will be regarded to be statistically significant. Students t--test and chi--sqare test will be used as appropriate. As it is common practice, results of Likert--like scales will be treated as interval--measures and thereby analysed by using parametric tests [Norman et al. 2010, Cariio et al. 2008. Local data management will be done using Microsoft Excel for Mac (Microsoft Corporation, USA) and R for Mac (R Foundation for Statistical Computing, Vienna, Austria) for statistical analysis. [R_Development_Core_Team 2009] Graphics will be created using PraphPad Prism for Mac (GraphPad Software Inc., La Jolla, USA).

Description of study days
Volunteers will be invited to participate in the trial by the study personnel. Recruitment will be conducted at a Training Centre of St. John ambulance, Vienna, Austria, before the starts of the lessons. After giving written informed consent, participants will be randomized using a web based randomization program Seite 8 von 13 (www.random.org) and allocated to perform standard CPR or CC only. The randomization for group allocation will be kept in opaque and sealed envelopes.
The evaluation will be performed with an independent investigator using a computer attached Resusci--Anne Skillreporter by Laerdal--Medical® and the Laerdal Skillreporter Software with Segstat (Version 2.3.0, Laerdal Medical, Stavanger, Norway).
The participants will be asked to perform BLS for five minutes on a manikin. The participants will then be asked to undertake any action they deem necessary to rescue the person simulated by the resuscitation manikin. Participants will not be informed about the underlying hypothesis or the outcome parameters. The room will be prepared to minimise outside interruptions.
Additionally, participants will be instructed to indicate the point in time during CPR when they feel that their fatigue is affecting the quality of the life support performed. ("During CPR and without stopping your actions, please tell us "NOW" when you perceive your fatigue is affecting the quality of the life support performed.) Participants in both groups will receive one of the charts right at the beginning of the scenario with the information that "this chart will provide information on how to perform CPR" and with the start of the clock further instructions regarding is content. Both groups will not receive any further introduction or support. At the beginning of the scenario, the manikin will be positioned in a supine position on the floor. There will be no clock visible for the participant while performing CPR. An investigator is acting as bystander able to call the emergency medical service or to be sent to look for an automated external defibrillator (which will not be available in the scenario). Nonetheless, the investigator is instructed not to provide any information on how to perform CPR and does not physically take part in the primary check, CC, or mouth--to--mouth ventilations.
Data of steps performed or left out will be documented in hardcopy on the case report form by an investigator and the exact times and details of chest compressions and ventilations will be documented electronically (Laerdal Skillreporter Software with Segstat (Version 2.3.0, Laerdal Medical, Stavanger, Norway)). Checklists of necessary steps will be created based on the ERC BLS Guidelines 2010 in the same manner as published previously [Roessler et al. 2007, Koster et al. 2010.
After the five--minute period has ended, the participants will be informed that the emergency medical service is now taking over and that they can stop performing CPR. Directly thereafter, they will be asked the following questions "How exhausted are you now on a scale from 1 to 10, where 1 indicates no exhaustion at all and 10 Seite 9 von 13 maximum exhaustion?" (Lickert Like 1--10). If a participant choses to abort resuscitation attempts before the five minutes are over, the open--ended question "Why did you discontinue the resuscitation attempts?" will be raised.

Risk/benefit assessment:
Apart from physical strain such as muscle pain or abrasion on the palm of the hand or knee after delivering chest compressions, there is no direct risk as the consequence of participation in the trial. To ensure participants added value, detailed information about the ERC CPR algorithm will be given after data collection.
This information included written material on the 2010 CPR guidelines, or the 2015 CPR guidelines when available.

Acknowledgement/approval of the study
Before the start of the recruitment, the trial will be submitted for approval to the Research Ethics Board of Medical University of Vienna.

Insurance
No insurance necessary.

Confidentiality
All subject names will be kept secret in the investigator's files. Subjects will be identified throughout documentation and evaluation by the number allotted to them during the study. The subjects will be told that all study findings will be stored and handled in strictest confidence.

Documentation of study findings
All findings collected during the study will be entered on the case report forms provided by the Medical Simulation and Emergency Management Research Group, Department of General Anaesthesia and Intensive Care Medicine. All entries in the case report forms will be made legibly in black ink. If corrections are made to entries in the case report form, the words or figures will be ringed and a single stroke drawn through them.
The correct value will be entered beside the old entry and the correction will be dated and initialled. Incorrect entries must not be covered with correcting fluid, or obliterated, or made illegible in any way.

Publication of study results
The findings of this study will be published by the investigators in a scientific journal and presented at scientific meetings. The manuscript will be circulated to all co--investigators before submission.

Authorship
The principle investigator will be the first author, PD Dr. Bernhard Rössler. Senior--, and corresponding author will be Assoc. Prof. Dr. Karl Schebesta. Authorship will be granted for substantial contribution to the project.
Supporting organisations will be acknowledged in the appropriate section of the final manuscript.