Background: Cardiac arrest is the number one cause of mortality in the Canadian population. Out-of-hospital bystander cardiopulmonary resuscitation (CPR) is associated with a 3 to 4 fold increase in survival for cardiac arrest. Any interruption in the delivery of chest compressions to cardiac arrest victims is detrimental on survival. In an effort to minimize interruptions in chest compressions, the new International Guidelines changed the long-recommended 15:2 compression to ventilation ratio to 30:2. Although the 30:2 ratio is meant to increase survival for cardiac arrest, the ability of rescuers to deliver the new CPR ratio intervention has never been studied. Little is known about the potential impact of the new recommendations on bystander fatigue and resulting CPR quality.