Susan Jeffrey

November 16, 2014

CHICAGO — A randomized comparison of mechanical vs manual compressions for cardiopulmonary resuscitation (CPR) shows no advantage for mechanical CPR on 30-day survival.

The results of the Prehospital Randomized Assessment of a Mechanical Compression Device in Cardiac Arrest (PARAMEDIC) trial were published online November 16 to coincide with their presentation here at the American Heart Association (AHA) 2014 Scientific Sessions Resuscitation Science Symposium.

"On the basis of ours and other recent randomized trials . . . the evidence available suggests this does not improve survival," lead author Dr Gavin D Perkins, Warwick Clinical Trials Unit, University of Warwick, Coventry, United Kingdom, concluded.

"Our interpretation is that while the device didn't improve survival, it retains certain practical advantages such as safety and quality of CPR in the back of a moving vehicle and when transferring a patient to the emergency department," Dr Perkins told Medscape Medical News. "It also frees up a pair of hands at a resuscitation attempt to attend to other tasks."

Ambulance service directors may choose to introduce or continue to use mechanical CPR as a practical solution to the challenges of prehospital resuscitation, he said. "If ambulance services do invest in the devices, it is vital that they spend sufficient funds to ensure adequate training and quality assuring during their use."


Currently, about one in 12 victims of cardiac arrest in the out-of-hospital setting survive and return home, the researchers point out. Chest compressions of sufficient depth and rate with full recoil of the chest between compressions and avoiding interruption are "crucial" to survival, they note, but this can be difficult, with factors such as small numbers of crew members, fatigue, patient access, competing tasks, and doing CPR in a moving vehicle interfering with high-quality compressions.

Dr Gavin Perkins

Mechanical compression devices have been developed to automate and potentially improve prehospital CPR. The device used in this study, the LUCAS-2 (Physio Control) is a battery-powered device designed to deliver quality compressions — 4 to 5 cm in depth at a rate of 100 per minute in continuous mode, with a ratio of 30 compressions with pauses to allow for two ventilations.

A study published earlier this year, the LUCAS in Cardiac Arrest (LINC) trial, compared the device as part of a new resuscitation algorithm, Dr Perkins noted during his presentation. "The conclusion of this study was that in clinical practice mechanical CPR using the presented algorithm did not result in improved effectiveness compared with manual CPR," he said.

The PARAMEDIC trial was a "pragmatic" trial designed to assess device use under real-life conditions in front-line emergency-response vehicles compared with standard CPR for resuscitation of nontraumatic out-of-hospital cardiac arrest. Investigators used a cluster-randomized, open-label design involving four ambulance services (West Midlands, North East England, Wales, and South Central England), with 91 urban and semiurban ambulance stations. Ambulance staff were trained to use the device with a clinical algorithm developed by the clinical educator staff within each of the four services.

Clusters were ambulance service vehicles, which were randomly assigned in a 1:2 ratio to mechanical or manual CPR. Patients received LUCAS-2 mechanical chest compression or manual chest compressions according to the first trial vehicle to arrive on scene, Dr Perkins noted.

The primary outcome was survival at 30 days following cardiac arrest and was analyzed by intention to treat. Ambulance dispatch staff and those collecting data on the primary outcome were masked to treatment allocation. Masking of the ambulance staff who delivered the interventions and reported initial response to treatment was not possible.

The researchers enrolled 4471 eligible patients, 1652 of whom were assigned to the LUCAS-2 group and 2819 to the control group between April 15, 2010 and June 10, 2013. In total, 985 (60%) patients in the LUCAS-2 group received mechanical chest compression and 11 patients (less than 1%) in the control group received mechanical compression, they report.

In the intention-to-treat analysis, 30-day survival was similar between groups.

30-Day Survival With Mechanical vs Manual CPR

End Point LUCAS-2, (n=1652) n (%) Manual CPR, (n=2819) n (%) Adjusted Odds Ratio (95% CI)
30-Day Survival 104 (6) 193 (7) 0.86 (0.64 – 1.15)

Similarly, there was no significant difference in secondary outcomes, including return of spontaneous circulation, survived event, and 3-month survival, "but there was a small difference in the proportion of patients with a CPC [Cerebral Performance Categories] score of 1 or 2 favoring the control arm," Dr Perkins reported.

No serious adverse events were noted. Seven clinical adverse events were reported in the mechanical CPR group (three patients with chest bruising, two with chest lacerations, and two with blood in the mouth). Fifteen device incidents occurred during operational use. No adverse or serious adverse events were reported in the manual group.

"In conclusion, this trial was unable to show any superiority of mechanical CPR and highlights the difficulties of training and implementation in real-world EMS systems," the authors write.

Deployment of mechanical devices across entire services will require substantial capital investment, they point out.

"This investment must be balanced against the accepted role such devices will continue to have when manual CPR is impractical or at increased risk (eg, in a moving ambulance)," the authors write. "Where organizations decide to adopt mechanical CPR it seems essential that sufficient resources are made available to support initial and regular refresher training and ongoing quality assurance. Future research should look to define the optimum method and frequency of such training."

Complexity of Resuscitation Trials

In an accompanying comment, Drs Marcus Eng Hock Ong and Venkataraman Anantharaman, from department of emergency medicine, Singapore General Hospital, point out that the appropriate role for mechanical compression devices in the prehospital setting has been debated in recent years.

"The quality of manual cardiopulmonary resuscitation during out-of-hospital cardiac arrest is often less than optimum and affects survival," the editorialists write. "Mechanical compression devices are an attractive alternative: they never get tired, give consistent chest compressions, and allow CPR to continue during transfer of the patient."

Results from real-world studies have suggested higher rates of return to spontaneous circulation and survival to discharge, but results from three randomized trials have not shown a significant survival benefit for mechanical vs manual CPR, they note.

PARAMEDIC researchers should be "commended" for attempting a real-world clinical trial, and their study "portrays the complexities and difficulties surrounding large-scale resuscitation trials and the importance of attention to implementation and training in the assessment of any new technology," they write.

"The somewhat low device usage rate (60%) reported in this study was due to difficulties in device use (15%), unknown reasons (6%), and noncompliance (16%)," Drs Ong and Anantharaman write. "Even with apparent compliance, whether operational issues resulted in implementation delays with the mechanical device is unknown. The absence of difference (or even inferiority) in outcomes in the trial group might not be due to the treatment or device itself, but to attention to training, compliance to protocols, and implementation."

About 60% of cardiac arrests attended were deemed not eligible and had no resuscitation attempted, which is "rather high compared with that in many EMS systems internationally."

"Although this study does not give us a definitive answer to the debate between manual and mechanical CPR, it does throw a spotlight on implementation and quality," they write. "EMS services should aim to provide the best quality of CPR possible. High-quality manual CPR requires EMS commitment to training and quality review. Mechanical CPR requires the same commitment to training and attention to deployment practices. Mechanical CPR is also more costly than manual CPR."

EMS systems worldwide routinely transport patients with cardiac arrest to the hospital with ongoing manual CPR of "doubtful quality," they conclude. "Safety concerns for unrestrained crew using manual CPR in a moving ambulance are real. Mechanical CPR allows crews to be safely belted up and is a logical choice from the safety perspective."

PARAMEDIC was supported by the National Institute for Health Research Health Technology Assessment (NIHR HTA) program, United Kingdom. Dr Perkins and other coauthors report receiving grants from the NIHR HTA program during the study. The other authors declare no competing interests. Dr Ong is principal investigator of an industry-funded study involving a mechanical CPR device; has received grants from Laerdal Medical, grants and personal fees from Zoll Medical, and nonfinancial support from Bard Medical and Zoll Medical; and has a patent method of predicting patient survival licensed to Zoll Medical and a patent system and method of determining a risk score for triage pending. Dr Anantharaman is principal investigator in an industry-funded study on use of a mechanical CPR device in the out-of-hospital situation; has received nonfinancial support from Physio-Control; and is a member of the medical advisory board of Falck Foundation.

Lancet. Published online November 16, 2014. Abstract, Comment

American Heart Association 2014 Resuscitation Science Symposium. Abstract 10. Presented November 16, 2014.


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