I WATCH BOX I
I RATE MATTERS I
In the December 2011 Research Review column, I reviewed the
National Institutes of Health Resuscitation Outcomes Consortium
(ROC) study that evaluated the impedance threshold device (ITD) in
a large multi-center clinical trial called the PRIMED trial (published in
the New England Journalof Medicine in September 2011). It reported
no difference between use of an active ITD and a placebo (or sham)
ITD. This has always puzzled me because I have used an ITD for years
and have seen it work.
In November 2012, Ahamed Idris, MD, presented an abstract
at the American Heart Association (AHA) Resuscitation Science
Symposium (ReSS), reporting that chest compressions for patients
in the ROC database weren’t necessarily performed at the 100 per
minute rate recommended in the study protocol or by the AHA; in
fact, more than half of the more than 10,000 patients received chest
compression rates that were too slow (less than 90 per minute) or
too fast (greater than 110 per minute). The data showed that the
faster the chest compression rate, the worse the outcomes.
This is reminiscent of the findings of Thomas Aufderheide, MD,
that hyperventilation is deadly in cardiac arrest. The ROC study confirmed that for chest compression rates, like ventilation, more is not
better, and in fact, more can be harmful. Idris presented additional
ROC data that shed new light on my confusion about the ITD’s previously reported efficacy. He reported that there was a significant
interaction between chest compression rate and ITD efficacy. Their
adjusted model predicted greater survival to discharge when the
ITD was used at AHA-recommended compression rates of around
100 per minute, compared with conventional CPR without an active
ITD at similar rates. Clearly, CPR needs to be performed correctly in
order to fairly assess new technologies like the ITD.
Idris and colleagues are planning to follow up the paper
soon. If the paper mirrors the abstract, we will see the first randomized, controlled, double-blinded clinical trial to demonstrate
that the ITD improves survival to hospital discharge with favorable
neurologic outcome with properly performed chest compressions.
What we know: Compression rates affect survival rates. The faster the compression rates, the worse the outcomes.
What this study adds: When an ITD is used as intended (at AHA-recommended
chest compression rates), observed survival-to-hospital discharge is considerably increased compared to CPR without an ITD.
Learn more from David Page at the EMS Today Conference & Expo, March 5–9 in
David Page, MS, NREMT-P, is an educator at Inver Hills Community
College and a paramedic at Allina EMS in Minneapolis/St. Paul.
He’s a member of the Board of Advisors of the Prehospital Care
Research Forum and the JEMS Editorial Board. Send him feedback at
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