CPR, CPR and more CPR

A short time ago an awkward adolescent Fire Medic nerd watched his hot swim instructor demonstrate how to pinch the dummy’s nose and perform mouth to mouth respirations. It seems shocking now to consider performing such an intervention without any form of PPE/BSI. Consider other relics of resuscitation procedures. One of my former Chiefs described an 80’s EMS protocol to perform one minute of CPR, move the Px to the lawn, perform an additional minute of CPR and then continue to the ambulance. After three explanatory attempts I still do not understand the compression, ventilation and vital signs check system my Mom was taught in the early 90’s.

The algorithms of CPR are a continually evolving process. The first recorded account of successful artificial respiration was in 1775 and involved a coal miner who had been overcome by fume inhalation (ref: Hermreck, 1988). In 1960 Kouwenhoven et al published a study describing their successly administration of thoracic compressions in 20 cardiac arrest patients (ref: Hermreck, 1988). CPR has continued to evolve into the algorithm we currently use to treat the 162,200 cardiac arrests that occur out of the hospital each year (ref: Rosamond et al, 2008).

The current dominating body in resuscitation guidelines is the International Liaison Committee on Resuscitation (ILCOR). ILCOR relies on volunteer research performed by experts from around the world. The results are published in Circulation and Resuscitation as International Consensus on CPR and ECC Science with Treatment Recommendations (CoSTRs). These CoSTRs are discussed at a large conference held once every five years. The next conference will be held next month in Dallas, Texas.

Rumours have abounded within pre-hospital care circles that ILCOR may remove ventilations from lay rescuer CPR. Many with whom I have discussed the topic are surprised at the idea. Especially considering the emphasis currently placed on airway management and effective ventilation for the patient (A & B before C). So what is driving this theory? Part of the motivation behind removing ventilations is that to perform them a single rescuer must interrupt chest compressions. In a recent tongue in cheek titled article, Do Not Pardon the Interruption, Bobrow et al discuss the growing body of evidence suggesting the strongest indicator of improved patient outcome in cardiac arrest is reducing the number of compression interruptions (ref: Bobrow, 2009).

Two studies have found that CPR providers, both in and out of hospital, were doing something other than compressing the chests of their Px 24-49% of the time (ref: Bobrow, 2009). Additional indicated interventions such as endotracheal intubation can take up to two minutes to perform and account for up to a quarter of these interruptions yet provide little additional benefit to the Px (ref: Wang et al, 2009). Although the presence of an AED is associated with an increase in Px survivability Bobrow et al suggests a round of compressions before applying the AED pads as well as utilizing single shocks as opposed to “stacked” successive shocks. EMS algorithms which include these suggestions are correlated with a three-fold improvement in Px outcome (ref: Bobrow, 2009).

Alright so I understand it is important to prevent compression interruptions, but surely you don’t mean we will not ventilate our Px? What happened to “a Px without an airway is a dead Px”? It may be the case that ventilations are not a life-critical component of CPR. A study analyzed the effects of three compression to ventilation ratios as well as compressions-only procedure in pigs. Researchers anaesthetized 40 pigs and then used a right ventricle pacing electrode to set them into ventricular fibrillation (VF). They found that although peripheral oxygen saturation was lower in the compressions-only condition broad outcome measures, including neurological function and 24-hour survival, did not vary across the four conditions (ref: Sanders et al, 2002).

There may be additional benefits to removing ventilations from CPR other than preventing interruptions. Bag Valve Mask (BVM) ventilation can easily lead to hyperventilation. Hyperventilation can, paradoxically, lead to reduced perfusion as stacked breaths increase the intrapleural pressure and impede venous return not to mention the airway complications from vomiting as a result of gastric insufflation (ref: Compression only CPR). It is also conceivable that cardiac arrest Px would have an increased probability of receiving bystander CPR if said bystander was no longer required to plant his face onto a complete stranger.

We as pre-hospital care providers will probably witness significant changes after the 2010 ILCOR conference as well as in the near future. Research abounds in areas of resuscitation such as therapeutic hypothermia, pharmacology and CPR protocols. Great for the Px, bad for adolescent boys forever deprived of tricks to make-out with their hot lifeguards.

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