Mechanical Cardiopulmonary Resuscitation (mCPR)

The author has no conflicts of interest related to any of the devices mentioned in this article.

OVERVIEW

Mechanical cardiopulmonary resuscitation (mCPR) devices are automated devices that provide chest compression during cardiac arrest, without the need for human-performed manual compression.

• mCPR devices are also known as automated chest compression devices, and primarily refer to load-distributing band devices and pneumatic piston devices
• Manual compressions remain the standard of care for CPR
• mCPR devices have not been shown to be superior to manual compressions
• Many centers and services use mechanical CPR devices in circumstances where the perceived benefits outweigh the perceived harms

Other devices and techniques, not covered by this article, have also been proposed as adjuncts or alternatives to manual compressions but are not widely used or lack ‘real-world’ effectiveness:

• High impulse external chest compression devices
• Interposed abdominal compression
• Active compression-decompression CPR devices
• Impedance threshold valves
• Phased chest and abdominal compression
• Vest CPR

RATIONALE

Early CPR is associated with increased survival and is a key part of the chain of survival for cardiac arrest.

• Well performed chest compressions during cardiac arrest only achieves 20-30% of normal cardiac output
• Manual compressions are subject to human error and inter-individual variation; rescuer fatigue affects CPR quality after the first minute of CPR and the practitioner is often unaware of the deterioration in performance (Hightower et al, 1995; Ochoa et al, 1998)
• mCPR devices have many potential advantages (see below)… but disadvantages too!

TYPES

The main types of mCPR devices currently in use are:

1. pneumatic piston devices (e.g. Michigan® and Lucas®), and
2. load-distributing band devices (e.g. Zoll AutoPulse®)

Lucas® device

• A pneumatic piston device
• Lucas2® device is most commonly used, although the Lucas3® device is now available
• Specific features:
  • only for use in adults; contraindicated in very obese or pregnant patients
  • Creates an active ‘decompression suction’ on upstroke
  • More portable than the Autopulse (can be moved in bag and easily assemble)
  • Easy to fit, small backboard can even be slid uber most patients in a supine or semi-supine position
  • Can work off a mains power supply or battery source (battery easy to change)
  • Can be more difficult to identify malposition during use
  • Noisier than AutoPulse®

Zoll AutoPulse® device

• Has a load-distributing compression band that compresses the entire thorax, including the heart
• Specific features
  • Only use in patients under 130kg
  • Only use in patients over the age of 18
  • Only use in ‘non traumatic’ cardiac arrest
  • Some argue that the circumferential band is less traumatic than thumper or manual CPR; however some studies suggest the opposite
  • Yellow stripe allows relatively easy visual alignment of correct positioning
  • Need to either sit patient up or roll on side to place backboard (during an interruption to manual CPR)
  • Less noisy than pneumatic compression devices
  • Has a radio-opaque backboard
  • Difficult to release the battery for replacement and power switch is eaily hidden by the patients head and hair

ADVANTAGES

Advantages of mCPR include:

• mCPR allows chest compressions to be performed with consistent quality
  • Important in situations such as prolonged retrieval, post-thrombolysis (PE or MI), hypothermia, cardiotoxic overdose, transfer to cath lab or for ECMO-CPR
• Defibrillation can be safely performed during compressions
• Potential for decreased interruptions to compressions (for defibrillation or change of personnel during manual compressions)
• Avoids exhaustion from prolonged manual chest compressions
• Allows safe performance of chest compressions during retrieval and in confined spaces (e.g. ambulance or aerial retrieval)
• Allows ‘cognitive offloading’ and frees up personnel (team leader role and decision-making is potentially more effective when fewer people are needed, there is less ‘cross-talk’, and there are fewer tasks to be performed)
• Requires less personnel to maintain ongoing CPR (e.g. sole operator in remote location, or prolonged CPR to the cath lab)
• Can facilitate percutaneous coronary intervention (PCI) and initiation of ECMO during CPR

DISADVANTAGES

Disadvantages of mCPR include:

• Not found to be superior to manual compressions in major studies (CIRC, LINC, and ParaMeDiC; see below)
• Requires staff training and familiarity with equipment setup, positioning, and operation
  • A “pit crew” protocol can decrease setup times (Ong et al, 2013)
• Cost and availability issues
  • Purchase, replacement of consumables, maintenance, cleaning
• Equipment or battery failure can lead to prolonged interruptions in CPR
• May be ineffective for certain body types (“one size does not fit all”)
• Prone to malpositioning over time
• Well-trained individuals performing manual compressions may outperform mechanical devices
• Can cause patient trauma
  • E.g. rib fractures, gastric rupture, splenic rupture, liver laceration, and haemorrhage (from mediastinal, epicardial, pericardial, and aortic sites)
  • unclear if specifically related to specific mechanical CPR devices, mechanical CPR devices in general, or if due to prolonged CPR in general (See below)
• Adult devices are not suitable for paediatric patients
• Zoll AutoPulse® device has a radio-opaque backboard that makes percutaneous coronary intervention (PCI) during CPR more difficult

EVIDENCE

Summary

• Animal and experimental studies indicate that mCPR devices can provide efficient, standardised, effective CPR (e.g. Liao et al, 2010)
• A more recent observational study suggested worse outcomes with mCPR when used routinely for out-of-hospital cardiac arrest (e.g. Buckler et al, 2016), while older studies appear to favour mCPR (e.g. Ong et al, 2006)
• Recent major trials and systematic reviews (see below), overall, suggest that mCPR achieves similar outcomes to manual compressions but is not superior.
• Despite an overall absence of superiority for mCPR, there are patient subgroups (e.g. refractory cardiac arrest) and circumstances (e.g. austere environments, and during transport) where mCPR may be beneficial.

CIRC trial (Resuscitation, 2014)

• Multicenter randomized, unblinded, controlled group sequential trial of adult out-of-hospital cardiac arrests of presumed cardiac origin
• three US and two European sites from 2009 to 2011
• 4753 patients randomised after CPR initiated, but only 522 (11.0%) met post-enrollment exclusion criteria
• Intervention: mCPR with Autopulse (n=2099) (49.6%)
• Control: manual CPR (n-2132 (50.4%) M-CPR
• Outcomes
  • Primary outcome: survival to hospital discharge (analyzed adjusting for covariates: age, witnessed arrest, initial cardiac rhythm, enrollment site; and interim analyses) was 96 (9.4%) vs. 233 (11.0%) for Autopulse and control arms respectively. The adjusted odds ratio of survival to hospital discharge for Autopulse compared to M-CPR, was 1.06 (95% CI 0.83-1.37), meeting the criteria for equivalence
  • The 20 min CPR fraction was 80.4% for Autopulse and 80.2% for manual CPR
• Comments and criticisms:
  • Majority of patients were excluded post-randomisation for various reasons
  • Blinding was not possible due to intervention type
  • 20 min CPR fraction was high for manual CPR (possible Hawthorne effect?)
  • Was not powered for a longterm patient-orientated outcome, like 6-month neurological outcome.
  • Compression depth as an indicator of compression quality was not monitored
  • Significant conflicts of interest as the trial was funded by ZOLL Medical, who developed the CIRC trial protocol, and all authors’ institutions received funding from ZOLL for their participation in the trial
• Conclusion:
  • Compared to high-quality manual CPR, Autopulse resulted in statistically equivalent survival to hospital discharge

LINC trial (JAMA, 2014)

• Multicenter randomized clinical trial involving 4 Swedish, 1 British, and 1 Dutch ambulance services and their referring hospitals
• 589 patients with out-of-hospital cardiac arrest
• conducted between January 2008 and February 2013
• Patients were randomized to receive either:
  • mechanical chest compressions (LUCAS) combined with defibrillation during ongoing compressions (n = 1300),
  • or manual CPR according to guidelines (n = 1289)
• Outcomes
  • Primary outcome: four-hour survival rate of 23.6% with LUCAS and 23.7% with manual CPR (risk difference, -0.05%; 95% CI, -3.3% to 3.2%; P > .99)
  • No difference in the secondary outcome of good neurological recovery (Cerebral Performance Category (CPC) score of 1 or 2) at 6 months
• Commentary and criticisms:
  • Not generalisable due to the non-standard use of defibrillation in the LUCAS arm of the trial
  • The primary outcome of 4-hour survival is not a patient-orientated outcome, neurological survival is (but the trial was not powered for this).
  • Among patients surviving at 6 months, 99% in the mechanical CPR group and 94% in the manual CPR group had CPC scores of 1 or 2
  • Although protocol design was independent of Physio-Control/Jolife AB, they provided funding to the host institutions and the lead author had received consultation fees in the past, indicating significant conflicts of interest.
• Conclusion:
  • Among adults with out-of-hospital cardiac arrest, there was no significant difference in 4-hour survival between patients treated with the mechanical CPR algorithm or those treated with guideline-adherent manual CPR.
  • This trial lacks external validity.

PARAMEDIC trial (Lancet, 2015)

• A pragmatic, cluster-randomised open-label trial
• Included 4471 adult patients with non-traumatic, out-of-hospital cardiac arrest (OOHCA) from four UK Ambulance Services (2010-2013)
• Clusters were ambulance service vehicles, which were randomly assigned (1:2) to LUCAS-2 or manual CPR
• Patients received LUCAS-2 mechanical chest compression (n=1652) or manual chest compressions (n=2819) according to the first trial vehicle to arrive on scene
• Outcomes
  • The primary outcome was survival at 30 days following cardiac arrest: 6% in the LUCAS-2 group and 7% in the manual CPR group (adjusted odds ratio [OR] 0·86, 95% CI 0·64-1·15))
  • No serious adverse events were noted
• Comments and criticisms:
  • intention to treat analysis was used
  • Masking of the ambulance staff who delivered the interventions and reported initial response to treatment was not possible, but dispatch staff and those involved in data collection were masked
  • LUCAS-2 group findings:
    • 985 (60%) patients in the LUCAS-2 group received mechanical chest compression
    • Adverse events: three patients with chest bruising, two with chest lacerations, and two with blood in mouth
    • 15 device incidents occurred during operational use.
  • A mCPR trial conducted independently of industry!
• Conclusion:
  • no evidence of improvement in 30-day survival with LUCAS-2 compared with manual compressions for OOHCA.

Systematic Reviews

• Gates et al (2015) conducted a systematic review of 5 trials and found no evidence that suggests that mechanical chest compression devices are superior to manual chest compressions when used during resuscitation after out-of-hospital cardiac arrest (OOHCA)
• Couper et al (2016) conducted a systematic review of 8 trials and concluded that mechanical chest compression devices may improve patient outcomes when used for in-hospital cardiac arrest (IHCA), but that the quality of evidence was very low

AHA and ECC guideline recommendations (October 2015) for use of mechanical CPR devices:

• The evidence does not demonstrate a benefit with the use of mechanical piston devices / load-distributing band devices for chest compressions versus manual chest compressions in patients with cardiac arrest. Manual chest compressions remain the standard of care for the treatment of cardiac arrest, but mechanical piston devices may be a reasonable alternative for use by properly trained personnel. (Class IIb, LOE B-R)
• The use of mechanical piston devices / load-distributing band devices may be considered in specific settings where the delivery of high-quality manual compressions may be challenging or dangerous for the provider (eg, limited rescuers available, prolonged CPR, during hypothermic cardiac arrest, in a moving ambulance, in the angiography suite, during preparation for extracorporeal CPR [ECPR]), provided that rescuers strictly limit interruptions in CPR during deployment and removal of the devices. (Class IIb, LOE C-EO)

AN APPROACH

mCPR devices should not be used routinely

• They may be used when perceived benefits exceed the perceived harms
• Such situations may include:
  • During patient transportation, to allow ongoing CPR and avoid risk to healthcare providers
  • When staff or space is limited or CPR is prolonged
  • To allow interventions (e.g. in cath lab, ECMO CPR)

When mCPR devices are used their performance should be closely monitored:

• Ensure the mechanical CPR is properly positioned and functioning correctly
• Avoid interruptions in CPR (e.g. on initiation, if battery failures, when repositioning is needed, etc)
• Consider use of an arterial line to evaluate performance (well-trained humans may perform manual CPR better than mCPR devices in some circumstances)

References

Journal articles

• Buckler DG, Burke RV, Naim MY, et al. Association of Mechanical Cardiopulmonary Resuscitation Device Use With Cardiac Arrest Outcomes: A Population-Based Study Using the CARES Registry (Cardiac Arrest Registry to Enhance Survival). Circulation. 2016; 134(25):2131-2133. [pubmed]
• Couper K, Yeung J, Nicholson T, et al. Mechanical chest compression devices at in-hospital cardiac arrest: A systematic review and meta-analysis. Resuscitation. 2016; 103:24-31. [pubmed]
• Gates S, Quinn T, Deakin CD, et al. Mechanical chest compression for out of hospital cardiac arrest: Systematic review and meta-analysis. Resuscitation. 2015; 94:91-7. [pubmed]
• Hallstrom A, Rea TD, Sayre MR, et al. Manual chest compression vs use of an automated chest compression device during resuscitation following out-of-hospital cardiac arrest: a randomized trial. JAMA. 2006; 295(22):2620-8. [pubmed]
• Hightower D, Thomas SH, Stone CK, et al. Decay in quality of closed-chest compressions over time. Annals of emergency medicine. 1995; 26(3):300-3. [pubmed]
• Koga Y, Fujita M, Yagi T, et al. Effects of mechanical chest compression device with a load-distributing band on post-resuscitation injuries identified by post-mortem computed tomography. Resuscitation. 2015; 96:226-31. [pubmed]
• Li H, Wang D, Yu Y, et al. Mechanical versus manual chest compressions for cardiac arrest: a systematic review and meta-analysis. Scandinavian journal of trauma, resuscitation and emergency medicine. 2016; 24:10. [pubmed]
• Liao Q, Sjöberg T, Paskevicius A, et al. Manual versus mechanical cardiopulmonary resuscitation. An experimental study in pigs. BMC cardiovascular disorders. 2010; 10:53. [pubmed]
• Ochoa FJ, Ramalle-Gómara E, Lisa V, et al. The effect of rescuer fatigue on the quality of chest compressions. Resuscitation. 1998; 37(3):149-52. [pubmed]
• Ong ME, Ornato JP, Edwards DP, et al. Use of an automated, load-distributing band chest compression device for out-of-hospital cardiac arrest resuscitation. JAMA. 2006; 295(22):2629-37. [pubmed]
• Ong ME, Quah JL, Annathurai A, et al. Improving the quality of cardiopulmonary resuscitation by training dedicated cardiac arrest teams incorporating a mechanical load-distributing device at the emergency department. Resuscitation. 2013; 84(4):508-14. [pubmed]
• Perkins GD, Lall R, Quinn T, et al. Mechanical versus manual chest compression for out-of-hospital cardiac arrest (PARAMEDIC): a pragmatic, cluster randomised controlled trial. Lancet (London, England). 2015; 385(9972):947-55. [pubmed]
• Rubertsson S, Lindgren E, Smekal D, et al. Mechanical chest compressions and simultaneous defibrillation vs conventional cardiopulmonary resuscitation in out-of-hospital cardiac arrest: the LINC randomized trial. JAMA. 2014; 311(1):53-61. [pubmed]
• Smekal D, Johansson J, Huzevka T, et al. A pilot study of mechanical chest compressions with the LUCAS™ device in cardiopulmonary resuscitation. Resuscitation. 2011; 82(6):702-6. [pubmed]
• Wik L, Olsen JA, Persse D. Manual vs. integrated automatic load-distributing band CPR with equal survival after out of hospital cardiac arrest. The randomized CIRC trial. Resuscitation. 2014; 85(6):741-8. [pubmed]

FOAM and web resources

• Emergencypedia — Push my buttons: mechanical CPR (2014)
• EP Monthly — Mechanical CPR takes a thumping (2014)
• INTENSIVE — Aus-ROC Seminar on Mechanical CPR (2014)
• INTENSIVE — Video: How to use an Autopulse and Video: How to use a LUCAS2 (2014)
• LUCAS — LUCAS Device (manufacturer information)
• Resus Room — Mechanical CPR podcast (2017)
• Resus.ME — Not finding a difference doesn’t prove equivalence (2014)
• SGEM — SGEM#136: CPR – Man or Machine? (2015)
• St Emlyns — JC: PARAMEDIC trial m-CPR (2014)
• Zoll — Autopulse device (manufacturer information)