The Science Behind Compressions Explained

[This is as reported by Richard Huff in JEMS]


Richard Huff, EMT-B | | Friday, March 4, 2011

The new 2010 American Heart Association ECC guidelines were designed to get around things that didn’t work for years—and were not backed by science, according to Joseph Ornato, MD, professor and chairman of the Department of Emergency Medicine at the Virginia Commonwealth University Health System.

“We’ve really had to admit in many cases, the science isn’t there to support the things we’ve done in the guidelines for decades,” Ornato told attendees at the EMS Today Conference & Exposition in Baltimore.

“We’re really trying to be brutally honest and not get distracted by things that really don’t work,” Ornato says, “and rather do a handful of things that do work, and really pound home the realization of those elements.”

Late last year, the guidelines were released, putting an emphasis on chest compressions. The guidelines upended the previous thinking that had rescuers providing ventilation before beginning compressions and the rapid introduction of defibrillation.

However, research showed that compressions first provided better results. Likewise, going to compressions first also encourages bystanders to get involved where they might not have in the past because of fears of doing mouth-to-mouth resuscitation.

Ornato says the notion of compressions first—and an emphasis on uninterrupted chest compressions—actually surfaced much earlier in Europe.

“The Europeans were kind of way ahead of us in being enlightened in terms of what the sequence is,” he says. “We’ve finally come around to admit they were kind of right from the beginning.”

The new compressions-airway-breathing model works best with witnessed cardiac arrests in public places, he says. Part of that is because folks who go down in public places tend to not be high-risk patients with underlying health issues. Part is also the ability of bystanders to get involved quickly and begin the process of resuscitation before trained rescuers arrive.

“What we’re left with us resuscitation and rescue, and that’s of course, a very time critical and very much dependent on us in EMS to stretch the window of time, to get help there quickly, and to get the help of bystanders,” says Ornato, who’s also the medical director for the Richmond (Va.) Ambulance Authority.

He says the good part is that most adults have pulseless ventricular tachycardia when they arrest in a public place have, and most of those people have plenty of oxygen in their lungs to be moved by compressions only.

Without effective chest compression, oxygen flow to the brain and heart stops, drugs that could help aren’t circulated, and ultimately, defibrillation is ineffective. Also, practice is required to minimize the interruptions in chest compressions to deliver a shock, he says.

Compressions build coronary perfusion pressure, he says. And research has indicated it can take 10 compressions after a rescuer stops compressions for ventilation or another intervention before the pressure is back up. He says data indicates an estimated three to five percent of EMS calls are for cardiac arrest.

Ornato says the National Institute of Health is preparing to launch a randomized test to measure the concept of whether everyone should be doing continuous compressions; they’re hoping to get 12,000 cases examined.

On the ALS side, quantitative waveform capnography is the most reliable method to confirm and monitor correct endotracheal (ET) tube placement, Ornato says. He noted a study in Orlando where one in four ET tubes were misplaced, a figure that dropped to zero after capnograpy was introduced.

He also says, the fifth link in the chain of survival is post-cardiac arrest care, which was added to emphasize the importance of comprehensive multi-disciplinary care through hospital discharge and beyond.

Ornato says it was “a very exciting time in resuscitation and it’s rapidly evolving.”