These notes are from an episode of 7 Things EMS, a podcast created to give you CE while providing important, relevant information to make you a better provider. This episode is 7 Things Resuscitation with Bobby Wales, who was the Director of Education for the American Heart Association.
Resuscitation Need-to-Knows for EMS Providers
Below you’ll find important notes about CPR and defibrillation in out-of-hospital cardiac arrest. In the 7 Things podcast, we talk to Bobby Wales about the science and highlights of resuscitation and how the American Heart Association (AHA) guidelines are meant to be used. It’s a great episode, and you can get CE for it! Get it here.
High-Quality CPR Cannot Be Replaced by Any Advanced Intervention
It’s all about the CPR. Many factors play an important role in resuscitation – like team dynamics, pharmaceutical interventions, and electrical interventions – but high-quality CPR has the greatest impact on survival to hospital discharge.
Here are the five key components of CPR. Hopefully you know these, but we’re going to put them out there anyway:
- Pushing hard. 2 to 2.5 inches
- Pushing fast. Choose your preferred rhythm-setter: the classic Staying Alive, the grim Another One Bites the Dust or The Imperial March from Star Wars.
- Allow full recoil. You don’t need to remove your hands, but make sure your hands aren’t putting any pressure on the chest between compressions. The heart needs to have full opportunity to refill with blood before you compress again.
- Don’t hyperventilate. Give just enough ventilation to see the chest rise, which is about 500 to 600 mL in the average adult patient. Hyperventilation increases the pressure in the chest too much and reduces blood flow back to the heart.
- Minimize delays in chest compressions. The best way to measure this is to use chest compression fraction. Chest compression fraction is the amount of time that chest compressions are being actively given divided by the total amount of time for the resuscitation. So if the total resuscitation time is 140 seconds and 115 seconds are spent doing compressions, the chest compression fraction looks like 115 / 140 = 0.82. That’s 82%. The ideal percentage is at least 80% or 90%.
It’s a good idea to use audio-visual feedback devices to provide feedback on the quality of CPR. As providers perform the skill, these devices ensure that they’re giving the correct compression technique. Trials have reported up to a 25% increase in survival to hospital discharge when audio feedback devices are available to give depth, recoil, and rate feedback. Physiological measurements like end tidal CO2 or blood pressure are helpful too, but they don’t offer the instant feedback of audio devices that tell you how you’re doing on chest compressions.
Early Defibrillation is Critical to Survival from V-fib and Pulseless V-tac Cardiac Arrest
After CPR, early defibrillation is the most important factor in survival for these patients. We see strong evidence that defibrillation is most successful when administered early after the onset of pulseless V-tac or V-fib. There’s some evidence that biphasic defibrillators have greater success in terminating arrhythmias. Various other devices deliver different forms of shock waves, but there’s no evidence that one is better than the other in terms of shock wave.
The current recommendation is to only provide a single shock and then immediately resume CPR – this guideline might surprise some people who have worked in EMS for many years. (No more stacked shocks. Shock shock shock epi shock is outdated.)
The American Heart Association used to give a lot of recommendations around energy doses, but these days, the amount of energy delivered varies by manufacturer. Many manufacturers measure the impedance of the chest, i.e., how much tissue is blocking the electrical conduction. So for a very thin person, the monitor may say they don’t need as high of a dose, while it would probably deliver a higher dose for a very large person. So now the AHA simply says you should follow the manufacturer’s recommendations for whatever device you use. Ideally, you want to provide compressions while the defibrillator is being applied or charged, clear for the shock, and immediately after the shock is delivered, resume CPR.
Compressions > shock > immediate CPR
There’s no need to stop and look for a rhythm – another recommendation that might be new to you if you’ve been in the field a while. Just go right back to CPR and perform high-quality CPR for 2 minutes until it’s time to reanalyze and, if needed, defibrillate again.
For the BLS provider, the pattern is the same for a pulse check: If the patient isn’t showing signs of life, don’t stop for a pulse check; get right back to compressions.
Most AEDs now allow you to resume compressions after analysis and during charging, so you’re not off the chest too long. If you’ve used AEDs a lot, you know that it takes eight seconds to analyze, then it’s going to take another five or six seconds to charge, and then you can shock – so by the time you get off the chest, analyze, shock, and get back on the chest, you could easily have a 20-second delay. That’s why the AHA recommendation is to resume compressions while the AED is charging and then stop again to deliver the shock and resume immediately. It keeps you from being off the chest too long.
That said, some AEDs will continue to analyze through the shock or the charging period and doing compressions can interfere with their function. If you’re a BLS provider using AEDs, make sure you really know what AED you’re using – take the time to understand how it’s programmed, know how many seconds it takes to analyze and charge, and know if you can do compressions while it’s charging. The last thing you want is to have to learn how the AED is set up while you’re in the middle of a cardiac arrest situation.
Do You Do CPR Before Defibrillation in an Unwitnessed Cardiac Arrest?
The AHA makes its recommendations based on research and there’s not really any research that has looked at the difference between doing compressions or defibrillation in those initial seconds. What the research does say is that the earlier you can defibrillate, the better. However, in an EMS setting, it’s rare that a patient goes into cardiac arrest when you already have the pads on them, so in most cases, you’ll have a period of CPR while applying the monitor anyway. In the rare circumstance in which you have a patient who is clearly in a cardiac arrest condition, and you proactively attached the pads and see them go into V-fib, there’s no reason to delay shocking to start performing CPR.
In all circumstances, it would be reasonable to start with a shock as soon as you can effectively deliver it. Only when you can’t deliver it instantly (usually the case), you should immediately begin compressions while the AED gets set up.
About the Expert
Robert Wales, ALM, NRP, serves on the Board of Directors for the Commission on Accreditation for Prehospital Continuing Education (CAPCE), where he works to drive quality in EMS continuing education. He was the Director of Education for the American Heart Association (AHA) through 2022. In his role at the AHA, he oversaw the instructional design and educational support for programs that reach over 30 million learners each year. Prior to working for the AHA, Robert was a paramedic and Training Officer for Pickens County EMS in South Carolina. He has been in EMS for 20 years.