April 20, 2015

REBEL Cast Episode 8: The Skeptical Edition – Active Compression CPR with Augmentation of Negative Intrathoracic Pressure

Welcome back to a special edition, or should I say “skeptical edition” of REBELCast. We have started to do something new by inviting guests onto the show to discuss papers in the literature they find interesting.  This month I had the pleasure of working with Ken Milne, an emergency room physician in Canada. Today, Ken and I are going to specifically discuss a new device that recently got FDA approval for CPR in Out of Hospital Cardiac Arrest (OHCA), and the question we are trying to answer is:

Is active Compression Decompression CPR with Augmentation of Negative Intrathoracic Pressure for Treatment of Out-of-Hospital Cardiac Arrest superior to standard CPR?

REBEL Cast Episode 8: The Skeptical Edition – Active Compression CPR with Augmentation of Negative Intrathoracic Pressure

Click here for Direct Download of Podcast

Who is our guest this month on REBELCast?

Ken MilneOur guest this month is Ken Milne, MD (Twitter: @thesgem) who has a fantastic podcast of his own called The Skeptics Guide to Emergency Medicine or The SGEM for short. The SGEM is a knowledge translation (KT) project started in 2012. The goal of the SGEM is to cut the KT window from over 10 years down to 1 year. The SGEM does this by using social media to provide the audience with high quality, clinically relevant, critically appraised, evidence based information, so you can provide EM patients with the best possible care. The SGEM consists of a weekly blog and 20min podcast. Each week Ken invites a guest skeptic to perform a critical appraisal on a recent article while trying to find the right balance between education and entertainment.

Marshal Mcluhan

Finally, the SGEM uses a validated and reliable tool from the McMaster University the home of evidence based medicine. The tool comes from the Best Evidence in Emergency Medicine (BEEM) group. It is used to probe the literature.

The SGEM

Topic: Active Compression Decompression CPR with Augmentation of Negative Intrathoracic Pressure

Question: Is active Compression Decompression CPR with Augmentation of Negative Intrathoracic Pressure forTreatment of Out-of-Hospital Cardiac Arrest superior to standard CPR?

Article: Aufderheide et al. Comparative Effectiveness of Standard CPR versus Active Compression Decompression CPR with Augmentation of Negative Intrathoracic Pressure for Treatment of Out-of-Hospital Cardiac Arrest: Results from a Randomized Prospective Study. Lancet. 2011 January 22; 377(9762): 301–311. PMID: 21251705

Background: Sudden cardiac arrest is very common and in the United States, there are about ½ a million cardiac arrests every year. About half of these cardiac arrests are out-of-hospital cardiac arrest and the survival rate is pretty poor with recent survival estimates of 7 – 9.5%.

Details of the Study:

  • Population: Adults with OHCA of presumed cardiac origin
    • Excluded:non-cardiac arrests, trauma, stroke, over dose, electrocution
  • Intervention: Active Compression Decompression (ACD) CPR with Augmentation of Negative Intrathoracic Pressure
  • Comparison: Standard CPR
  • Outcome: Primary was survival to hospital discharge with good neurologic function (modified Rankin Scale of three or less)

Results:

  • The survival to hospital discharge with a modified Rankin Score of three or less:
  • 75/840 (8.9%) vs. 47/813 (5.8%), p=0.019, OR 1.58 [CI= 1.07, 2.36].
  • They report this as 53% relative increase in survival (absolute was 3.1% NNT=33)
  • If you had used mRS of two or less the results are 6.2% vs. 4.6% (absolute difference 1.6% NNT=63) favoring the intervention.
  • The HARM: increase pulmonary edema in intervention group

Limitations:

  • This was an industry-sponsored trial: This does not negate the results but should always make people a bit more skeptical. The sponsor helped in designing the study, data interpretation, writing and decision to submit the paper for publication.
  • The study was terminated early due to lack of funding: The original study called for total of 1,400 patients. A pre-planned interim analysis recommended upping the sample size to 2,700 to have 80% power to detect a difference. At the time of termination they had only enrolled 1,653 patients. This means there were 1,000 patients (37%) short of required target size. This limits making any strong conclusions on the primary outcome and severely limits any comments that could be made about secondary outcomes and subgroup analyses.
  • The two groups were not treated equally post randomization. The intervention group received much greater cardiac care:
    • Cardiac catheterization (33% vs. 42%)
    • Coronary stenting (13% vs. 16%)
    • Coronary bypass surgery (3% vs. 6%)
    • Cardio-defibrillators (14% vs. 17%)
  • This trial was registered at ClinicalTrial.gov. While some of the secondary outcomes were reported others were not. This included the survival at 30 days and the neurological recovery at 30 days on mRS. There were three other neurologic scores collected but not reported. They only reported the Cognitive Abilities Screening Instrument (CASI) at 90 and 365d (not at 30d). They did not report the following outcomes at discharge, 30d, 90d or 1 year:
  • Cerebral Performance category (CPC)
  • Overall Performance Category (OPC)
  • Health Utilities Index Mark 3 (HUI3)
  • They present a Beck’s Depression Index, which was not in their original 2005 study design or updated secondary outcomes in 2012.

What is the clinical bottom line for the above clinical question?

  • It is not clear if this device works in improving survival with good neurologic outcomes for patients with OHCA, but this study does not prove that it does.
  • The other take home point would be – Remember to be skeptical of anything you learn, even if you heard it on the Skeptics’Guide to Emergency Medicine or in this case REBELCast!!!

Be sure to checkout REBEL EM on some of our other social media platforms:

Cite this article as: Salim Rezaie, "REBEL Cast Episode 8: The Skeptical Edition – Active Compression CPR with Augmentation of Negative Intrathoracic Pressure", REBEL EM blog, April 20, 2015. Available at: https://rebelem.com/april-2015-skeptical-edition-rebelcast/.
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Salim Rezaie

Emergency Physician at Greater San Antonio Emergency Physicians (GSEP)
Creator & Founder of R.E.B.E.L. EM
7 Comments
  • Ken Milne
    Posted at 16:21h, 23 April Reply

    Thanks for inviting me to be a “skeptical” guest on REBEL Cast.

  • LITFL Review 179 | LITFL
    Posted at 16:00h, 26 April Reply

    […] Milne and Salim Rezaie team up on REBEL Cast for a critical appraisal of active compression-decompression CPR with augmentation of negative intrathoracic pressure in out-of-hospital cardiac arrest. […]

  • Salim Rezaie
    Posted at 06:20h, 06 May Reply

    Hello readers,
    I always want to make sure that we have full transparency when discussing research articles on the blog and podcast. I received an email from someone I will keep anonymous, but I feel there points should be heard along with the podcast. The email I received is as follows:

    I was disturbed by your podcast. It was completely one-sided and showed no respect for the investigators. So forgive me if I sound abrupt…..

    ….This podcast is not just skeptical, it is kind of nihilistic, and there is innuendo that someone intentionally mislead the readers.

    No therapy rests only on one trial. You guys don’t touch on all the previous literature and experimentation on the augmentation of blood flow by these devices. History is ignored.

    You approach it as if it is published in a vacuum. So there is no discussion of why one should temper the skepticism, no positive approach whatsoever.

    Skepticism sounds to young doctors like intelligent discussion. To old folks like me, it can sound naive and sophomoric, as if the skeptic doesn’t know much about the topic and like the skeptic has done little research himself.

    It is very easy to criticize; it is very difficult to create.

    This trial will never be done again and no trial of any CPR device will ever be funded again.

    If your opinions were widespread, there would never be progress in this dismal science.

    Why don’t you talk to Keith Lurie himself, if you want some real thoughtful discussion from a true master and expert? Or if you just can’t trust him because he owned the company that funded the project, talk with Demetris Yannopoulos, who has no financial interests.

    These guys are revolutionizing CPR in ways you cannot imagine. They are actually doing something.

    Maybe he has time for an interview. I’m not sure. I’ll ask him for you if you want.

    I would recommend that, at the very least, when you guys have your skeptical entertainment, that you at least congratulate the investigators for their incredible work, their incredible dedication, and their amazing creativity.

    Show some respect.

    • Salim Rezaie
      Posted at 06:21h, 06 May Reply

      My reply to this email was as follows…..

      I appreciate the fact that you spent the time to send me an email and the fact that you were disturbed by the podcast simply means that you care, which is exactly why I do the podcast (i.e. because I care too). The purpose of the podcast was to do a mini critical appraisal of a study purely going over the facts of the study. The specific issues we discussed with this particular article were:

      1. A modified Rankin Score of 3 was used, when most literature uses a modified Rankin Score of 2. A modified Rankin Score of 3 has relative increase in survival of 53% & absolute increase of 3.1%, if you use a modified Rankin Score of 2 the absolute increase in survival is only 1.6%. Why was a modified Rankin Score of 3 used and only relative increase used?

      2. On the clinicaltrial.gov site it states that some of the secondary outcomes to be included were cerebral performance category, overall performance category, and the Health Utilities Iindex Mark 3 at 30d, 90d, and 365d but instead survival and a mRS of 3 at 30 days were what were reported. Why weren’t all the secondary outcomes reported as the study was registered?

      3. Finally, the conclusion of the podcast was not “nihilistic,” but instead and I am quoting here: “I am not sure if this device works in improving survival with good neurologic outcomes for patients with OHCA. What I am sure about is this study does not prove that they do. I am not prepared to reject the null hypothesis that there is no difference.” So nowhere was our conclusion that this device doesn’t work, but instead this one paper doesn’t prove that it does.

      At no time was our intention, and I have relistened to the podcast, to be disrespectful to anyone. I would love an opportunity to answer the above questions with either Keith and/or Demetris and also happy to put it up as a part two to the original podcast.

      Sincerely,

      Salim

  • Sunny
    Posted at 11:52h, 18 May Reply

    There will never be another CPR device study EVER? What other things does he know about the future?

    • Salim Rezaie
      Posted at 12:14h, 18 May Reply

      Hello Sunny,
      I am not sure about the future myself, but I think it is important to discuss facts of studies, and even the facts I write should be questioned. I have been known to make mistakes, so I felt it was important to put the email on the blog, so if others have questions, they too can review the study and see what they think. Appreciate you reading and listening.

      Salim

  • LITFL Review 179 • LITFL Medical Blog • FOAMed Review
    Posted at 21:21h, 03 January Reply

    […] Milne and Salim Rezaie team up on REBEL Cast for a critical appraisal of active compression-decompression CPR with augmentation of negative intrathoracic pressure in out-of-hospital cardiac arrest. […]

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