Background:

More than two thirds of sudden cardiac arrests are witnessed by bystanders. Bystander cardiopulmonary resuscitation (CPR) doubles survival from cardiac arrest. Importantly, even in witnessed cardiac arrests only 20% of the bystanders commence basic life support. Common reasons for not commencing include panicking and the perceived inability to perform CPR correctly. A meta-analysis could demonstrate that a simplification 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, the investigators wanted to test the hypothesis that chest compressions (CC) are delivered more correctly regarding the depth when utilizing the standard Basic Life Support (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.

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 (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 European Resuscitation Council (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 maximum exhaustion?" (Lickert Like 1-10). If a participant chooses to abort resuscitation attempts before the five minutes are over, the open-ended question "Why did you discontinue the resuscitation attempts?" will be raised.

Inclusion Criteria:

• Volunteers of non-medical professions

Exclusion Criteria:

• <18years
• medical professionals
• known pregnancy
• physical impairments or illnesses that prohibited physical