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Chest Compressions during Defibrillation

Chest Compressions during Defibrillation

Arguabley one of the most regimental, most empahised, most scripted part of CPR and AED training comes at the point when the defibrillator is about to deliver a shock. Relgiously we practicsed making sure that we, and others around us were clear of a casualty right before we pressed the flashing red button. Often instructors would take note of the way in which you pressed the button so that, if you happened to look at the button when you were pressing it; Failed, now let's try it again! 

Tried and Tested

The procedure for using the AED on a victim and delivering a shock usually goes something like this:

  1. The AED instructs to stop CPR while analysing.clear
  2. The AED would recognise the rhythm.
  3. The AED would indicate shock or no shock.
  4. If shock indicated, restart CPR until the AED is charged.
  5. Once the machine is charged clear the victim.
  6. "I'M CLEAR, YOU'RE ARE CLEAR, WE'RE ALL CLEAR"
  7. Place a finger on the button.
  8. Extend your arm from head to toe ensuring nobody is touching the victim.
  9. While looking at the victim, press the shock button. 
  10. Restart CPR with compressions.

If you can carry out the procedure like that, then most would agree that you are doing in right and using the machine in a safe mannor. It is a scenario that has been practised countless times by first aiders, responders and practitioners up and down the country. 

Safety

Instructors would argue, possibly rightly so, that there are serious safety risks for people who are in contact with the victim when the shock is being delivered. The explanations given usually relate to the passage of electricity through the body and how it is designed to stop the heart. This might also say to students, that the only time the machine is dangerious is when it is charged and ready to give a shock. Think about it, we want people to have a certain amount of respect for this machine, after all it is going to stop someones heart. Let's not mess around with it. When using it we need to make sure we do so effectively and safely.

Research

Research published in the American Heart Association Circulation Journal (http://circ.ahajournals.org/) in 2008[1] looked at the electrical current flow through rescuers in direct contact with patients during biphasic external defibrillation. The basis of the study was: The safety of a rescuer remaining in contact with a patient being shocked with modern defibrillation equipment has not been investigated.

What they did

This study measured the leakage voltage and current through mock rescuers while they were compressing the chests of 43 patients receiving external biphasic shocks. During the shock, the rescuer's gloved hand was pressed onto the skin of the patient's anterior chest. To simulate the worst case of an inadvertent return current pathway, a skin electrode on the rescuers thigh was connected to an electrode on the patient's shoulder. In no cases were shocks perceptible to the rescuer. The average leakage current flowing through the rescuer's body for each phase of the shock waveform was 283+/-140 microA (range 18.9 to 907 microA). This was below several recommended safety standards for leakage current.

What they concluded

Rescuers performing chest compressions during biphasic external defibrillation are exposed to low levels of leakage current. The present findings support the feasibility of uninterrupted chest compressions during shock delivery, which may enhance the efficacy of defibrillation and cardiocerebral resuscitation.

In Response

In response to the study there were a number of letters [2][3] received which raised a couple of issues.

  1. In the study the rescuers wore gloves, in the real world gloves are not always worn.
  2. The movement of the body during the shock, along with the compression force experted by the rescuer might cause injury to the victim and or the rescuer.
  3. The electrical isolation of the gloves can not always be guranteed as they are manufactured to different standards, to different weights and sometimes with different material.

Further Development

There have been other studies that examined the feasability of "Hands-On" defibrillation. One particular bovine study looked at the possiblity of using an aide to help rescuers isolate themselves from the victims. The "Rescusication Blanket"  protecting the rescuer from the risk of receiving electrical current during defibrillation which would allow for uninterrupted chest compressions. The study showed that when the blanket was used and "hands-on" defibrillation was carried out there was some voltage recorded. When the blanket was not utilised they found a decrease in the coronary perfusion pressure and end-tidal CO2 where the hands were removed for the purpose of charging. Their conclusion overall was: - The resuscitation blanket is a safe and useful tool which protects the rescuer from hands-on defibrillation shocks, allowing for uninterrupted chest compressions, therefore improving defibrillation success.

 

Conclusion

While this practice is not likely to change overnight, with more of these types of studies and further developement of aides like resusciation balnkets and gloves specifically designed to allow defibrillation with continious compressions, it is not beyond the realms of possiblilty that one day we will see the introduction of continious chest compressions while defibrillations is in progress. 

References

1. Circulation. 2008 May 13;117(19):2510-4

2. Circulation. 2008; 117: 2435-2436

3. Circulation. 2008; 118: e712

4. Resuscitation. 2010 Feb;81(2):230-5

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