CPR in Out of Hospital Cardiac Arrest: Man vs Machine

26 Oct
October 26, 2015

CPR - Man vs MachineBackground: In cardiac arrest, high quality, uninterrupted CPR is essential to help improve survival rates. In theory, mechanical CPR should provide CPR at a standard depth and rate for prolonged periods without a decline in quality, which should help improve survival and survival with good neurologic outcomes. There are many types of mechanical chest compression devices but the two main technologies can be generalized as piston devices and load-distributing bands. The piston driven devices work by compressing on the chest in an up and down type of motion, similar to how we do manual CPR. The load distributing bands wrap all the way around the chest and shorten and lengthen which provides more of a rhythmic type of chest compression. No individual trials have ever shown superiority on clinically important outcomes for adult patients with OHCA, regardless of device.

What Article are we Discussing?

  • Gates S et al. Mechanical Chest Compression for Out of Hospital Cardiac Arrest: Systematic Review and Meta-Analysis. Resuscitation 2015; 94: 91 – 97. PMID: 26190673

What They Did:

  • Systematic review of studies evaluating effectiveness of mechanical chest compressions vs manual chest compressions in adult patients with Out of Hospital Cardiac Arrest (OHCA)
  • Good Neurologic Outcome defined as Cerebral Performance Category (CPC) ≤2 or Modified Rankin Scale (mRS) Score ≤3

Outcomes:

  • Return of Spontaneous Circulation (ROSC)
  • Survival of Event
  • Overall Survival
  • Survival with Good Neurologic Outcome

Trials Included:

StudyYearNumber of ParticipantsInterventionCountry
ASPIRE2006767AutoPulseUSA/Canada
Smekal2011148LUCASSweden
LINC20142589LUCAS/LUCAS-2Sweden, UK, Netherlands
CIRC20144231AutoPulseAustria, Netherlands, USA
PARAMEDIC20154471LUCAS-2UK

Results:

  • 5 Trials included
    • 3 Evaluated LUCAS or LUCAS-2 Devices
    • 2 Evaluated Autopulse Device
  • No Advantage of Mechanical Chest Compression Devices for:
    • ROSC (OR 0.96)
    • Survival of Event (OR 0.95)
    • Survival to Discharge or at 30 days (OR 0.89)
    • Survival with Good Neurological Outcomes (OR 0.76)

Strengths:

  • Used Cochrane Risk of Bias tool to assess studies’ risk of bias
  • Very low proportion of missing outcome data (But in some trials missing data in the assessment of neurologically intact survival was missing, which could cause potential bias)

Limitations:

  • No blinding of clinicians providing care

Discussion:

  • This review looked at 5 randomized trials, with over 10,000 patients with OHCA and found no evidence of benefit with the use of mechanical chest compression devices, but lets be clear, it also found no evidence of harm.
  • There are very wide confidence intervals despite the large number of patients, and this is most likely due to the low survival rate from OHCA
  • Quality of CPR provided in the manual CPR arms was not documented in studies. This is an important point that cannot be emphasized enough. If manual CPR was high quality, then maybe mechanical devices may not seem as good, but if the CPR was low quality, then mechanical devices may be better.
  • Another issue is in the 2006 ASPIRE trial mechanical CPR was at a rate of 80 compressions/min and manual CPR was at 100 compressions/min. This would falsely lower the usefulness of mechanical CPR as we know the appropriate compression rate is 100/min.
  • Another issue is that in the 2006 ASPIRE study, time to defibrillation was 2.1 minutes longer than the manual CPR arm. In the LINC trial, time to defibrillation was 1.5 minutes longer than the manual arm. We know that early, high-quality CPR + early defibrillation are keys to successful survival with good neurologic outcome.
  • CPR is a means to an end. In other words doing high quality, uninterrupted CPR is important, but this is not the end point. Instead this is a way to continue to perfuse the brain while we figure out what caused the OHCA. Therefore, mechanical CPR is a way to cognitively offload our minds about depth of compressions, rate of compressions, while we try and figure out why our patient arrested.
  • Mechanical CPR still has a role in my opinion. Imagine working in an ED where you are the lone doctor with minimal staff. You only have so many people that can perform CPR before they get tired and the quality of the CPR decreases. Imagine another scenario like being on the back of an ambulance or a helicopter as a patient is being transported. Surely, mechanical CPR will be higher quality and safer for the crew than manual CPR? I would consider using mechanical CPR over manual CPR in the following scenarios:
    • Limited rescuers available
    • Prolonged CPR
    • CPR in a moving ambulance or helicopter

Author Conclusion: Existing studies do not suggest that mechanical chest compression devices are superior to manual chest compression, when used during resuscitation after OHCA

Clinical Take Home Point: This is not the end of mechanical compression devices as none of the studies showed harm with these devices. Use of these devices may cognitively offload providers to focus on the cause of the arrest instead of ensuring the quality of the CPR.

References:

  1. Gates S et al. Mechanical Chest Compression for Out of Hospital Cardiac Arrest: Systematic Review and Meta-Analysis. Resuscitation 2015; 94: 91 – 97. PMID: 26190673

For More Thoughts on This Topic Checkout:

Post Peer Reviewed By: Matt Astin (Twitter: mastinmd)

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Salim Rezaie

Emergency Physician at Greater San Antonio Emergency Physicians (GSEP)
Creator & Founder of R.E.B.E.L. EM

Latest posts by Salim Rezaie (see all)

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5 replies
  1. Scott Cooper says:

    I absolutely love mechanical compression devices!! Unless I have a supply of 25yo athletes that are all the same height, I choose mechanical over people in the ER or on the street. It doesn’t even need research proven analysis. If it creates a pulse, doesn’t injure the dead person and saves my back for the next patient, I’m in.. I may have thought different when I was a 6′ 220lbs athletic male but now I am a 5’11” 260lbs non-athletic male. Side note: I do not like machines that say “push harder, deeper or push faster” but I imagine most of us males don’t ever ever want to hear those words. Seriously, the machine now makes me think twice before wanting family with the patient work up because of the loud speech of a dumb machine that makes the compressor sound like he/she is doing something wrong. That is team leads job.

    Reply
    • Salim Rezaie says:

      Hey Scott,
      Really appreciate you weighing in. I have also found that when I am running a code, instead of focusing on the quality of the CPR that is being given, it is a cognitive offload. So if I do have a long code, I do think about using it. Appreciate your thoughts and weighing in on the conversation.

      Salim

      Reply
  2. Bill Warsing says:

    Not superior to human providers but dose not cause harm.

    I view this as a win for correctly utilized mechanical devices. We are quickly headed into the age of Cardiocerebral Resuscitation where on-scene efforts may last 30min or more. I personally believe a device that can reasonably provide consistent rate and depth (and recoil) over a long code will prove itself in ‘lives saved with brain intact’ over future studies.

    If the Lucas group were smart, they’d cut the laughably ridiculous luxury-item price and market these as standard-of-care devices before someone does it cheaper and beter.

    Reply

Trackbacks & Pingbacks

  1. […] week’s SGEM reviews the evidence for mechanical CPR. Don’t forget to check the recent REBELCast on the same topic. […]

  2. […] EM offers an excellent critique of the recent systematic review and meta-analysis of mechanical CPR devices in cardiac arrest. […]

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