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The Case for CPR Feedback Devices


When William Kowenhouven, Guy Knickerbocker and Peter Safar first identified an effective method of performing CPR in the 1960s, it promised to revolutionize emergency medicine. In 1994, a study on bystander CPR demonstrated this life-saving technique didn’t have to be limited to professionals—that anyone could step in to help—a concept that could, in theory, increase survival rates significantly. Soon after, the AED promised to continue the revolution: The sooner you defibrillate a patient in v fib, the better the chance for them to survive. Some even predicted AEDs would render CPR obsolete.

And yet, after so many years, after so many innovative leaps forward, cardiac arrest survival rates remain low in most communities.

To be sure, part of the reason is that the window of opportunity to save a patient in cardiac arrest is narrow, and requires a confluence of factors. But John Freese, MD, director of prehospital research for FDNY, believes there’s still room for improvement, and that the key lies in improving our CPR technique. And the key to that lies in CPR feedback devices.

There’s a lot that we still need to understand and study when it comes to delivering a successful resuscitation, but effective CPR forms the basis for our evolving definition. “We’re prescribing therapies we don’t know enough about to a disease process that we know even less about, to human beings that we may not know at all,” Freese says, paraphrasing Voltaire. “There’s a lot of work to be done, but CPR feedback seems to be our first step.”

The Failed Promise of Defibrillation
To understand why CPR feedback devices are needed, we first need to understand why AEDs failed to live up to their promise. After AEDs became available, defibrillation was one of the reasons behind the merger of the FDNY and New York City EMS—the thought was that it would reduce response times and double the number of defibrillators on the streets. Did it work? “Response time was reduced, from 9.3 minutes to 4.7 minutes,” Freese says. “That, combined with essentially doubling the number of defibrillators on the street, should have meant a dramatic increase in cardiac arrest survival. And yet, when you looked at it, the city saw only a small increase in cardiac arrest survival—2.2% to 2.9%.” And when you dig deeper into the statistics, you can see that when defined as return of spontaneous circulation (ROSC), survival actually decreased in the short term, from about 30% to 20%.

Importantly, Freese notes, this trend wasn’t unique to New York City. “Seattle seemed to experience a similar decrease in survival, from around 35% to 20%,” he says. “The problem seems to be the technological imperative—if you only give people a hammer, and endorse the amazing properties of the hammer, the world is going to be a nail. So what probably happened is that we forgot the other key components.”

Fewer Links in the Chain
For patients in v fib, all five links in the American Heart Association (AHA) chain of survival—rapid activation of EMS, early CPR, rapid defibrillation, effective ACLS and integrated post-arrest care—may apply. But Freese points out that for many patients, some of these links are deemphasized. “When you have short EMS response times, bystander CPR doesn’t improve survival, because EMS is there so quickly,” he says. “So you’re down to four links. But there’s a bigger problem, too. We’re seeing less and less v fib. In New York City in the 1990s, one in three patients presented in ventricular fibrillation. In 2012, it was one in eight.”

What does this have to do with CPR feedback? If we’re already providing early CPR, and if defibrillation won’t be effective, we’re now down to three links in the chain of survival where providers can impact survival rates. “For the majority of our patients, the chain of survival is just three links—someone calling us, us getting there and providing effective CPR, and getting them to appropriate post-resuscitation care,” Freese says. “And so for EMS, our link is CPR, regardless of their cause of arrest, regardless of the presenting rhythm.”

That means we better be extremely effective at it.

What Is Quality CPR?
Delivering high-quality CPR lies in understanding what high-quality CPR looks like. By now, most of us are familiar with the six key factors:

1. Compression depth of at least two inches.
2. Compression rate of at least 100 compressions per minute.
3. Allowing the chest wall to recoil fully between every compression.
4. Spending about 50% of the “duty cycle” of CPR actively compressing.
5. Limiting interruptions in CPR.
6. Ventilations of less than 10 per minute.

Unfortunately, knowing we need to perform CPR in this manner and actually doing it are two different things. “A JAMA study showed that the average compression rate is great, but with no feedback, the average patient ends up receiving just 18 effective compressions per minute,” Freese says, due to some not being deep enough and due to pauses in CPR. “That may help to explain the overall 3% survival rate to discharge for these patients.”

Fortunately, using CPR feedback devices has shown promise in improving CPR in real time. In 2009, FDNY purchased new monitors for the entire department, with the requirement that they be able to provide real-time audio and visual feedback.

As with any new technology, there are concerns that must be addressed. “Providers would say, you expect me to use a device that will say out loud, ‘Press deeper, press faster?’ This will put me at risk,” Freese says. “There were legal concerns, concerns about peer perception. It put pressure on our providers that we certainly didn’t intend.” Still, following lengthy discussions, the department’s ultimate decision was that visual and audio feedback was important. After training, the devices were deployed in 2011. Freese believes they are already having an impact.

One note of caution: It’s not enough to simply accept the data CPR feedback devices provide. You must dig into the data for the root causes behind what you’re seeing. If there’s a period where no compressions are being done, is that because the providers were intubating the patient or because the patient had a pulse? If the compressions were consistently too shallow, it could be provider performance, but there could be a patient physical attribute at play.

“If you just look at the data, it’s easy to target the providers who aren’t meeting standards,” Freese says. “But a ‘bad resuscitation’ on paper can actually be a good resuscitation.”

Initial Results
Because CPR feedback in real time is so effective, “most of the time, you’ll see great CPR,” Freese says. “But the question is, does that kind of data make a difference for our patients?”

In 2010, the AHA guidelines designated CPR feedback as effective in training, but noted that there was insufficient evidence to conclude that it had an impact on patient outcomes. In 2011, Freese notes, a study in the British Medical Journal designed to look at ROSC found that as compared to CPR with no feedback, visual and audio feedback provided no change in survival rates. “That study was published in 2011, but it was done prior to the release of the 2010 AHA guidelines, so the compressions were probably too slow and almost certainly too shallow,” Freese says.

So, the FDNY analyzed their data to get a better picture. And the results are promising. “We found that ROSC went from 38.5% in early 2011 when we first introduced the technology to 52.5% in June 2013,” Freese says. His conclusion: CPR feedback does improve at least short-term outcomes. He notes another recent study found that survival to hospital discharge for patients with witnessed ventricular fibrillation arrests was doubled through the use of audiovisual feedback, from 26% to more than 50%.

There’s clearly more research needed before we can truly understand the impact of real-time feedback on CPR quality. In the meantime, Freese argues that it’s our duty to embrace the technology. “Change is difficult to most of us in EMS,” he says. “Think about having to wear florescent vests, think about capnography. Think about when gloves weren’t an essential part of patient care. I think CPR feedback will take the same path as these things. Technology has to be a part of what we do. We have to be willing to use it and accept it because if we don’t, we’ll fall behind the times.” jems

Editor’s note: This article is adapted from the JEMS webcast, “The Weakest Link: Using CPR Feedback to Improve Quality.” View the webcast at www.jems.com/cpr-feedback-webcast.

12-Lead ECG Tips
Making the most of those squiggly lines

The 12-lead ECG is one of the most fantastic advances in EMS treatment since the invention of the bandage. The movement of this powerful diagnostic tool from the confines of the hospital to the streets has been nothing short of revolutionary. It has given EMS professionals a wealth of information on how to best care for our patients and has driven hospital care and the development of medical care practices by providing clear and critical data that physicians had rarely before seen.

Did you realize that by moving this tool to the field, EMS has almost made heart attacks into a minor medical complaint that can be effectively treated if caught early? EMS has changed healthcare with that. We’re catching things that used to go uncaught and have vastly improved the lives and qualities of life for countless patients who pass through our care. Kudos to the visionaries who helped drive this change. No matter the level of the service, be it ALS, ILS or BLS, a 12-lead ECG is an essential EMS tool and should be the standard of care.

Proper acquisition of the 12-lead ECG is paramount to getting the most out of this tool. An improperly acquired 12-lead doesn’t provide diagnostic-quality information and can render the tracing mostly useless. Here are a few tips to making sure you get it done right:

Lead Placement
Traditionally, the limb leads go on the limbs, and while it’s acceptable to move them closer if you have to, try to avoid placing the leads over bony prominences or overly fatty areas. Look for a generally flat, clean, intact area of skin with muscle generally underneath.

The V-Leads go on the chest in a specific pattern. Leads V1 and V2 go in the 4th intercostal spaces (between the ribs) on either side of the sternum. To find these, go about three finger widths up from the xyphoid process, or bottom of the sternum. V1 is on the patient’s right, V2 is on the left.

V4 should be placed next; it goes one rib down in the 5th intercostal space, on the midclavicular line. Place V3 in between V2 and V4.

V5 goes in the anterior axillary line (front of the armpit) and V6 goes in the mid-axillary line. They go in the same horizontal line as V4.

Skin Preparation
It’s important to prepare the skin by cleaning it with an alcohol prep and by abrading it with a cloth towel to remove dead skin cells. You may need to wash the area with saline and dry it. Remove excess body hair by shaving. For females, place the leads under the breast tissue. You may need to lift and clean the skin underneath the breast to get a clear tracing.

A quality 12-lead ECG has a smooth, flat baseline (called the isoelectric line). Baseline wander, or the vertical motion of the ECG line, can mask important findings in the ECG tracing and result in a non-diagnostic ECG.

The patient should remain motionless and lay as close to supine as possible for the acquisition of the tracing and the ambulance should be stopped and not moving during the process. It sometimes takes a few minutes for the ECG tracing to normalize and you should wait for it to do so. The goal is to be able to see the entire cardiac waveform clearly and be able to measure accurate ST-segment levels. Skin prep is important to reduce artifact. A tracing with artifact or baseline wander can mask serious ECG findings and may cause a patient to be misdiagnosed.

Multiple ECGs
One ECG is a spot-check of the patient’s heart. Two ECGs are a trend of their condition. Try to obtain a symptomatic tracing of the patient before treatments like oxygen, nitroglycerine or aspirin are given. Although you shouldn’t delay treatment, it’s been shown that ST-segment elevation can normalize quickly with EMS treatment and an ECG obtained afterward that doesn’t show ST-segment changes can mask a STEMI that should be emergently treated by a cath lab. The two or three minutes you spend taking the symptomatic ECG can save the patient hours or days going without definitive treatment for their underlying condition.

A good rule of thumb is to capture a 12-lead ECG tracing at the patient’s side where you find them symptomatic, then again when you load them in the truck, and then before you arrive at the ED.

Conditions Requiring an ECG
A 12-lead isn’t just for chest pain. Acquiring one never hurts any patient and may help catch the odd presentation of a serious but vague condition. Obtain a 12-lead for possible strokes, altered levels of consciousness, weakness, dizziness, fatigue, palpitations and otherwise vague medical complaints. Remember that diabetic patients, younger women and various ethnicities often have atypical presentations and may have “silent myocardial infarctions.” Be vigilant. You may just save a life.



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