updated Jan 2020 This document is the culmination of many hours of work by the leading researchers and healthcare providers studying emergency cardiac care and resuscitation. Research is constantly being done around the world in this field and it is a daunting task to review all of the various findings to develop a consensus for treatment of patients. A single study might have a strong positive finding, but that has to be confirmed by other studies and added to the overall body of research before it goes in to practice. The 2015 guidelines are the latest compilation of this research and this article will provide an overview of the findings relevant to lay rescuer CPR. One of the most notable changes in 2010 was reordering Airway, Breathing, and Circulation to Circulation, Airway, and Breathing. The CAB approach is reaffirmed as most beneficial by the 2015 guidelines. The benefit of placing circulation as the first step is that it decreases the delay between cardiac arrest and chest compressions being started. Chest compressions circulate blood and enable the brain to remain oxygenated leading to a greater likelihood that someone who survives cardiac arrest will leave the hospital without brain damage, or what is referred to as neurologically intact. 
In recognizing the importance of compressions the guidelines go on to fine tune the compressions being given. Simply providing compressions is inadequate, the compressions given must be high quality and some of the research done determined what factors lead to compressions not being high quality. 
Before discussing what areas need improvement let us define the pillars of high quality CPR. These areas are:


•  Providing chest compressions at the appropriate rate

•  Providing chest compressions at the appropriate depth

•  Ensuring the chest fully recoils between compressions

•  Decreasing interruptions in chest compressions

•  Limiting excessive ventilation (breaths given to a patient)




Regarding rate, the 2010 guidelines specified at least 100 compressions per minute, and while most instructors have been teaching 100-120 compressions per minute the upper limit had not been specified. The purpose of compressions is to squeeze the heart and circulate blood to the brain. If compressions are being done at a rate of greater than 120 compressions per minute the heart is not given adequate time to refill with blood resulting in less blood being pumped out and a decrease in survival with neurologic function intact. 
 Ideally, a victim of cardiac arrest will receive immediate care and their heart will be restarted which resumes blood circulation. This resumption of circulation is known as Return of Spontaneous Circulation or ROSC. Compressions given too fast also decrease the chance of ROSC, which is the immediate goal of all resuscitation efforts. 
 2015 has added an upper limit to the rate of compressions in an effort to improve patient outcomes. The recommendation is now no slower than 100 compressions per minute and no faster than 120 compressions per minute. 
 Another factor that impacts the quality of compressions is the depth to which the chest is compressed. 2015 Guidelines specific that the chest of an adult should be compressed at least 2 inches or 5 cm. The guidelines also note that compressing deeper that 2.4 inches of 6 cm may lead to harm. This is a guideline that while very specific is hard to take action on. Most CPR training manikins have some sort of feedback device indicating adequate depth but patients do not have such a device built in. Although training with manikins is useful the likelihood that someone will have enough practice with a manikin to develop the muscle memory to compress 2 inches but not 2.4 inches is low. As an aside, when the author was working full time (and then some) on ambulances in urban and suburban areas he would typically be on 10-15 cardiac arrests per year but even with quarterly training and those actual cardiac arrests it would be hard to say that every compression given was in that perfect zone between 2 and 2.4 inches. 
 There are commercially available devices that provide feedback while CPR is being done on a patient. The 2015 guidelines note "Compression depth may be difficult to judge without use of feedback devices” so the immediate thought is “well, just use a feedback device”. Not so fast. There are studies currently being done to test how effective CPR devices may be, but at least one previous study[i] found no improvement in the compressions delivered using a CPR feedback device and the delay to starting compressions due to using the feedback device could be devastating for a patient. 
 When taking a CPR class spending as much time as you can doing compressions on a manikin will help, especially if the manikin has a built in feedback device. If the manikin does not have a feedback device the instructor can give you pointers as you do compressions. 
 We have discussed improving rate and depth of compressions which are two of the four major points made by the update. The remaining two are regarding chest recoil and interruptions. 
Recoil is allowing the chest to fully re-expand after it has been compressed 2 inches by a rescuer performing CPR. There is a tendency for a rescuer to lean on the chest in the second between completing one compression and beginning the next. In that second the chest must be allowed to fully recoil so the heart may fill with blood which is then pumped out with the next compression. This is something that good CPR instructors will look for during practice sessions as it is usually an unintentional behavior. 
The fourth major point is regarding interruptions in compressions. One of the major trends in CPR guidelines and education has been to streamline the process and reduce how long it takes for someone to start compressions (for example moving away from ABC to CAB) and identify reasons why CPR is paused. One part of the process which has been identified is the time around when a shock is given by an AED. The guidelines have placed a greater emphasis on the importance of decreasing this time and instructors will be emphasizing this with their students. Compressions should continue throughout the setup and application of the AED until the AED directs compressions to stop so it can analyze the rhythm and again seconds before the shock is given. There is no reason to hold compressions after a shock has been delivered. The patient does not store any energy and will still need high quality compressions. 
An unfortunate, but increasingly common cause of cardiac arrest, especially in younger people is heroin overdose (or overdose of chemicals in the same family called “opioids”). The AHA has added two notes regarding these types of emergencies, one of which is specific to lay rescuer care. The AHA recommends that opioid overdose response education being provided to those at risk for opioid overdose as well as those living with or in regular contact with those are high risk. There is an antidote for opioid overdoses called naloxone and with overdoses becoming so widespread some states have made this available over the counter or have been giving it away to at risk individuals. Many people within public safety beyond those working on ambulances have now been trained in administering the antidote as well. The AHA notes that lay rescuer education is appropriate whether or not naloxone is being distributed. 




 The major takeaways from the 2015 updates for lay rescuers are: Rate: Compressions should be given between 100 per minute and 120 per minute. Depth: Compressions should be at least 2 inches or 5 cm but no more than 2.4 inches or 6 cm. Recoil: The chest must be allowed to fully recoil after each compression is given. Minimize Interruptions: The time between cardiac arrest and CPR being started must be decreased and the interruptions in compressions during CPR must be limited. [i] Zapletal, B. (2014). Comparing three CPR feedback devices and standard BLS in a single rescuer scenario: A randomised simulation study. Resuscitation, 85(4), 560-6. Retrieved from http://www.ncbi.nlm.nih.gov/pubmed/24215730 Also read : EMS1 AHA Guidelines review