According to the American Heart Association (AHA), more than 350,000 out-of-hospital cardiac arrests (OHCA) occur every year in the United States, with almost 90% mortality. On the other hand, 23.9% of individuals experiencing in-hospital cardiac arrest (IHCA) survive. The 2015 AHA guidelines emphasize the importance of high-quality CPR delivery, with attention to the rate and depth of chest compressions, full chest recoil, minimizing compression interruptions, and avoidance of excessive ventilation, to increase an individual's chance of survival.
Changes to know
The 2015 guidelines introduce new evidence-based treatments based on published research from a consensus of international experts. For OHCA, it's recommend that bystanders use a cell phone when calling for help. The AHA encourages untrained bystanders to call 911 and provide CPR with instructions from the dispatcher until emergency medical services (EMS) personnel arrive or an automated external defibrillator (AED) is retrieved. A Swedish study showed a significant increase in bystander initiation of CPR when mobile technology was used.
BLS sequence
Similar to the 2010 guidelines, the C-A-B (circulation, airway, breathing) approach is the recommended sequence when initiating CPR, rather than the A-B-C (airway, breathing, chest compressions) approach. When using C-A-B, chest compressions should be started right away and delays in ventilation should be avoided. A breathing and pulse check is limited to less than 10 seconds.
Rescuer-specific roles
The current cardiac arrest chain of survival is the same as the 2010 guidelines. Updates emphasize early dispatcher identification of cardiac arrest and early CPR to optimize outcomes. If the individual is unresponsive, there's a high possibility that he or she is in cardiac arrest. First, ensure the scene is safe, assess the individual's response, and call for help or 911. Rescuers' response to cardiac arrest is based on their level of training (see Rescuer roles).
Untrained lay rescuers should provide hands-only chest compressions with or without the guidance of a dispatcher until EMS arrives or an AED is available. In contrast, trained lay rescuers should provide chest compressions and ventilation at a ratio of 30:2 until EMS arrives or an AED is available. Before providing chest compressions and ventilation, healthcare providers should check for breathing and pulse at the same time to avoid a delay in compressions.
Defibrillation vs. CPR
The 2010 guidelines for OHCA recommended that first responders immediately perform CPR and utilize an AED when available. For IHCA, it was recommended that healthcare providers perform CPR until an AED is retrieved. There was an argument among experts as to whether early CPR or early defibrillation is more beneficial, especially in OHCA when an AED isn't readily available. Current research on unmonitored individuals experiencing OHCA due to life-threatening arrhythmias such as ventricular fibrillation indicates that initiating CPR for 1.5 to 3 minutes before defibrillation doesn't result in a significant benefit.
The 2015 update for witnessed cardiac arrest recommends an AED be used immediately once available. For unmonitored cardiac arrest, CPR should be maintained while an AED is retrieved. Once an AED is available, defibrillation must be immediately delivered after an "all clear" is announced and all individuals assisting with CPR have removed their hands from the patient's body. In any setting, after defibrillation, it's advisable to resume CPR without a rhythm check. A small, randomized controlled trial showed no benefit of a rhythm check after defibrillation.
Chest compressions
Chest compressions involve rate, depth, and recoil. High-quality CPR is crucial during cardiac arrest, including minimizing interruptions to maintain adequate compressions and avoiding excessive ventilation. The chest compression hand position at the lower half of the sternum remains unchanged.
Rate. The chest compression rate is defined as the expected frequency of chest compressions delivered per minute. The 2015 guidelines specify an upper limit compression rate of 100 to 120 per minute. Many studies showed that more compressions resulted in an increased survival rate compared with fewer compressions, which were associated with a lower survival rate. However, according to preliminary data, excessive compressions decrease blood flow and can have a negative outcome because they don't allow the heart enough time to fill with an adequate volume of oxygen-rich blood.
Depth. The 2010 guidelines recommended a compression depth of at least 2 in (5 cm). The 2015 update added an upper-limit compression depth of no more than 2.4 in (6 cm). In a small study of upper-limit compression depth, it was found that possible injuries may occur when the compression depth is more than 2.4 in.
Recoil. Full chest recoil means allowing the chest to return to normal position after chest compressions. It's practical to allow for full chest recoil to increase venous return because leaning on the chest prevents the heart from filling with blood.
Interruptions. Chest compression interruptions should be minimized to enhance the early return of spontaneous circulation. The 2015 update emphasizes a shorter pre- and postshock pause in chest compressions (less than 5 seconds). Several research studies demonstrated the negative impact on return of spontaneous circulation when compressions are interrupted too frequently. The 2015 guidelines recommend that the compression fraction should be greater than 60%.
Compression-to-ventilation ratio. The currently recommended ratio of 30 compressions to 2 breaths is similar to the 2010 guidelines for rescue breathing. However, if there's an advanced airway in place, 10 breaths should be delivered per minute (1 breath every 6 seconds) while chest compressions are performed continuously. For unresponsive individuals not breathing but with a pulse due to suspected opioid overdose, the administration of I.M. or intranasal naloxone is recommended.
Alternative techniques and ancillary devices
Conventional CPR involves manual chest compressions and mouth-to-mouth breathing that produce approximately 25% to 33% of normal cardiac output to support delivery of oxygen to the tissues. However, alternative devices that require specialized training are available to increase blood circulation during resuscitation, such as piston-driven compression devices. The 2015 guidelines discuss the limitations of these alternative devices based on extensive evidence.
Impedance threshold devices. These devices reduce intrathoracic pressure during periods of recoil by restricting unwanted inflow of air to the lungs. This promotes blood flow to the chest and increased venous return to the heart and vital organs. They can be attached to a face mask or endotracheal tube. A large, randomized, multicenter clinical trial showed no benefit or harm when using an impedance threshold device as an adjunct to conventional CPR. The 2015 update doesn't recommend the regular use of these devices during CPR.
Active compression-decompression CPR. This involves using a handheld suction cup applied to the midsternum to compress and decompress the chest after each compression. The decompression phase increases negative intrathoracic pressure during chest recoil to augment venous return. Reports of four randomized controlled trials of active compression-decompression CPR showed no difference in neurologic outcome or survival. The 2015 guidelines don't recommend the routine use of active compression-decompression CPR; however, it may be used as an alternative in settings with staff competently trained to use the equipment.
Mechanical chest compression devices. These devices are designed to maintain consistency in chest compressions and prevent interruptions. One device incorporates a suction cup attachment with a piston to facilitate active compression-decompression CPR. The load-distributing band is another example of a mechanical chest compression device that uses a constricting band and backboard for chest compressions. Both devices require readily available specialized equipment and properly trained staff to be effective. Reports of three large randomized controlled trials showed that mechanical chest compression devices didn't improve outcomes in OHCA compared with manual chest compressions. The 2015 guidelines don't recommend the routine use of mechanical chest compression devices; however, they may be used as an alternative in certain situations, such as in a moving ambulance or during prolonged CPR, when high-quality chest compressions are hard to maintain.
Extracorporeal CPR. This involves passing the individual's blood through an external device to provide oxygen. The aim is to support the individual while reversing the probable cause of cardiac arrest. The procedure requires proficiently trained clinicians, the availability of specialized equipment, and support from the multidisciplinary team. The use of extracorporeal CPR in a retrospective observational study of 120 IHCA patients showed a moderate benefit to patient survival at discharge and after 6 months postdischarge. However, another retrospective observational study of 118 IHCA patients showed no benefit to patient survival. Due to inconsistent results, the 2015 update doesn't recommend the use of extracorporeal CPR in the routine management of cardiac arrest.
Positive impact
The 2015 AHA guidelines focus on high-quality CPR, including a compression rate of 100 to 120 compressions per minute and a compression depth of no more than 2.4 in. Evidence shows that early CPR and defibrillation significantly impact cardiac arrest survival.
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