“While CPR has only been around in its true form for about 50 years, attempts at resuscitation date as far back as 1768, when the Dutch Humane Society was formed in an effort to improve resuscitation in drowning victims. Their first formal attempt at CPR included instruction on clearing the airway via rolling the victim over a barrel and hanging them upside down for several minutes.”
-EMS World 1
Cardio Pulmonary Resuscitation guidelines have seen many changes over the years, 2005 and 2010 seeing some of the most significant. Technique effectiveness has become the focus of intense study in spite of the challenges to collecting field data.
Just for fun, let’s review the reasons behind some of the American Heart Association guideline changes.
15:2 Gets the Boot
The University of Minnesota published a clinical and hemodynamic comparison between 15:2 and 30:2 C:V (compression to ventilation) ratios in CPR. Their test subjects were 20 female pigs and 20 BLS-certified rescuers. The results were this: “Compared to 15:2, 30:2 significantly increased diastolic blood pressure…; coronary perfusion pressure…; cerebral perfusion pressure…; common carotid blood flow…; end-tidal CO2…; and mixed venous oxygen saturation. Hemodynamics improved further with the ITD [Impedance Threshold Device]. Oxygenation and arterial pH were similar. Only one of nine pigs had return of spontaneous circulation with 15:2, vs. six of nine with 30:2 (p < 0.03).
Fatigue and quality of CPR performance were evaluated in 20 BLS-certified rescuers randomized to perform CPR for 5 mins at 15:2 or 30:2 on a recording CPR manikin. There were no significant differences in the quality of CPR performance or measurement of fatigue. Significantly more compressions per minute were delivered with 30:2 in both the animal and human studies.” 2 The obvious conclusion was that the “data strongly support the contention that a ratio of 30:2 is superior to 15:2 during manual CPR and that the ITD further enhances circulation with both C:V ratios.” Studies such as this one propelled the changes in American Heart Association guidelines.
(We will talk more about ITD’s in Part 2, I didn’t know what they were either 😉 )
Faster and Deeper
The most recent AHA guidelines changed the depths and rates/min for adult and child CPR to both faster and deep compressions. This was brought about after the “2010 international evidence evaluation process involve[ing] 356 resuscitation experts from 29 countries who analyzed, discussed, and debated the resuscitation research [of tens of thousands of peer-reviewed resuscitation studies]…over a 36-month period.” 3 Like I said- intense study. Check out the new rates/depths here if you aren’t sure…http://www.heart.org/idc/groups/heart-public/@wcm/@ecc/documents/downloadable/ucm_317350.pdf
ABC to CAB
The resuscitation sequence Airway-Breathing-Circulation was also changed in 2010 to Circulation-Airway-Breathing. The AHA states that, “The vast majority of cardiac arrests occur in adults, and the highest survival rates from cardiac arrest are reported among patients of all ages who have a witnessed arrest and an initial rhythm of ventricular fibrillation (VF) or pulseless ventricular tachycardia (VT). In these patients, the critical initial elements of BLS are chest compressions and early defibrillation. In the A-B-C sequence, chest compressions are often delayed while the responder opens the airway to give mouth-to-mouth breaths, retrieves a barrier device, or gathers and assembles ventilation equipment. By changing the sequence to C-A-B, chest compressions will be initiated sooner and the delay in ventilation should be minimal (ie, only the time required to deliver the first cycle of 30 chest compressions, or approximately 18 seconds; when 2 rescuers are present for resuscitation of the infant or child, the delay will be even shorter).” 4
Health care teams are often able to coordinate various resuscitation efforts simultaneously. Compressions still top the sequence list. However, with advanced training the resuscitation algorithm can be modified as per the cause of cardiac arrest. Enacting the “pit-crew” method of care will also be discussed in Part 2.
Look Ma! No lips!
2010 also saw the introduction of Hands-Only CPR for layman. First, this technique protects street rescuers from BSI issues if they don’t carry proper barrier devices. Ain’t no SARS for us!
Second, AHA states, “Hands-Only (lip-free-compression-only) CPR is easier for an untrained rescuer to perform and can be more readily guided by dispatchers over the telephone. In addition, survival rates from cardiac arrests of cardiac etiology are similar with either Hands-Only CPR or CPR with both compressions and rescue breaths.” 5
Hold the phone!? How is it possible that cardiac arrest casualties have similar outcomes regardless of rescue breaths? Ed Moser, the community education supervisor for Rural/Metro ambulance service in Syracuse makes a good point, “It is the [chest] recoil that is so important. When the chest recoils and comes back up, it causes a little vacuum inside the chest. That little vacuum inside the chest causes some air to go down the windpipe, and it causes some blood to come back from the lower extremities.”6
Oxygen levels are maintained in the blood for a few minutes after the heart stops beating, pair this with the vacuum created by compressions and the casualty should remain adequately oxygenated until a higher level of care arrives (within reason).
Nixing mouth-to-mouth also prevents the common mistake of hyperventilation. “If you breathe [too much] for me,” [Moser] explains, “you increase the inner thoracic pressure, and you decrease venous return. That’s bad.”7
Throughout the guidelines, AHA enforces that every level of provider should prioritize good compressions and early defibrillation. “Think of the body like those old-fashioned water pumps out in the country…You have to prime them with a few pumps to bring the water up, and you have to keep pumping so you don’t lose it. “If you wait too long, you lose that prime, and you have to start all over again…What you’re losing is the oxygen going to the head.”8 Ventilation efforts don’t mean jack if the oxygen-carrying blood isn’t being moved to vital organs.
Even defibrillation doesn’t amount to much if the “pump” is too dry. The heart muscle itself needs to be fed with oxygenated blood in order to function. CPR greases the gears so to speak- so when a normal rhythm is established through an electric shock the heart can contract effectively. The chances of returning to a normal rhythm decreases by 10% for every minute the heart is fibrillating (V-fib). Just like you can’t jump a completely dead battery, there is only a small window of opportunity when the heart is not beating normally but still carrying enough electricity to be converted.
Got all that?
There have been various other changes made which you can check out for free on the AHA website.
In Part 2 we will take a look at some new improvements being studied that we may see implemented in the future.
PS- Have you seen Chris Solomons Rescue yet?…So awesome! Caught on tape is the “Golden Eagle” of successful resuscitation. (May be disturbing to some).