Chest compressions have remained one of the most visible and effective components of prehospital resuscitation, dating back to the inception of modern emergency medical services (EMS). Although the idea and technique of chest compressions have not changed much over time, methods of mechanical cardiopulmonary resuscitation (CPR) have become increasingly available to prehospital providers. From their origins in the 1960s as inpatient piston-driven machines, mechanical CPR devices have become smaller and more easily used outside of hospital settings. These newer devices are quite costly to EMS agencies and some require single-use consumables – such as bands, batteries and suction cups – to be purchased throughout the lifetime of the device, only further increasing the cost.
Although no scholarly data exists regarding which mechanical CPR devices are used throughout the country, observational data suggests that the vast majority of devices are either the piston driven (Michigan and LUCAS devices) or load band distributing devices (Zoll AutoPulse). While minor differences exist between these products as a result of their design, the overall purpose of these devices is the same — to provide uninterrupted CPR regardless of the location, nature or duration of the EMS activation.
Interestingly, and as very recently reviewed in this journal, evidence for the use of mechanical CPR devices is lacking.1 Numerous studies have failed to find meaningful patient benefit to using mechanical CPR devices2-6 and a recent study of “pit crew” mechanical CPR, often cited as the ideal method to deploy mechanical CPR in the outpatient setting, found decreased return of spontaneous circulation (ROSC) and decreased survival to discharge.7 This latter “pit crew” approach to the utilization of mechanical CPR was particularly notable as some have suggested that prior studies did not take into account proper device deployment when evaluating patient outcomes. Taken together, the totality of currently available scholarly literature does not support the routine use of mechanical CPR for the majority of prehospital cardiac arrests. Yet despite this lack of evidence, anecdotal evidence suggested that mechanical CPR device use has been increasing across the country.
Importantly, while prior studies have primarily focused on the patient perspective when considering the deployment of mechanical CPR devices, there has been less attention to the benefits these devices may provide to EMS providers. Mechanical CPR devices allow for transport to the hospital with all EMS personnel seated with their seat belts applied during any transport. In cases of prolonged resuscitation, mechanical CPR devices can help prevent rescuer fatigue and potential injury from repeated motion. Finally, these devices can allow for EMS personnel to focus on other components of resuscitation such as intubation, medication administration and family support without worrying about ongoing compressions.
In this context of anecdotally expanding use despite limited evidence of patient benefit, we used the National EMS Information System (NEMSIS) data from 2010 through 2016 to characterize trends of mechanical CPR utilization.8 We found a statistically significant fourfold increase in mechanical CPR utilization, with large variations in use across communities and demographics (Tables 1-3 in our JAMA Network Open paper). We also noted that transport times tended to be quite short with both manual and mechanical CPR.
These findings were surprising for a number of reasons. First, our hypothesis of increasing use despite minimal evidence was clearly confirmed by the NEMSIS data. These data suggest that more patients were receiving mechanical CPR in the prehospital setting, likely due to increased deployment of these devices by agencies nationwide.
Second, there were clear demographic and geographic factors that were associated with the likelihood of receiving resuscitation with one of these devices. This variation in care is certainly not ideal for patients nationwide – if mechanical CPR were a truly superior modality, then we would have hoped to find minimal geographic and demographic variations in use. However, given that routine evidence does not support use of these devices, the differences in demographics and geography suggest that resuscitative care may be provided differently based on factors outside of the patient’s control.
Finally, one of the reasons cited for use of mechanical CPR devices was to facilitate transfer from the scene to the hospital with ongoing compressions. While compressions in the back of a moving ambulance is certainly challenging, we had expected prolonged transport times well beyond the average of nine minutes for cardiac arrest patients.
Based on our findings, we suggest that the use of mechanical CPR be revisited in the prehospital setting as a tool only in specific circumstances when manual CPR is not feasible. This conclusion is the same one reached by a recent Cochrane review,9 which also quite appropriately reminded readers that some studies have found the potential for patient harm when using these devices. Helicopter transports, long ground transports with a small crew, extrications or walk up buildings all may be reasonable use cases when manual CPR is simply not feasible. In these cases, rapid application, careful ongoing monitoring and avoidance of interruption in compressions as well as defibrillation are all necessary to ensure that the quality of mechanical CPR is as optimal as possible. More generally, EMS systems should also consider the need for such systems in their communities with a particular eye toward ensuring that the often limited EMS funds are spent where they are most needed.
1. Wacht O, Kohn J, Strugo R. Mechanical CPR Devices: Where is the Science https://www.jems.com/2019/11/12/mechanical-cpr-devices-where-is-the-science/. Published 2019. Accessed 12 November, 2019.
2. Bonnes JL, Brouwer MA, Navarese EP, et al. Manual Cardiopulmonary Resuscitation Versus CPR Including a Mechanical Chest Compression Device in Out-of-Hospital Cardiac Arrest: A Comprehensive Meta-analysis From Randomized and Observational Studies. Annals of emergency medicine. 2016;67(3):349-360 e343.
3. Gates S, Quinn T, Deakin CD, Blair L, Couper K, Perkins GD. Mechanical chest compression for out of hospital cardiac arrest: Systematic review and meta-analysis. Resuscitation. 2015;94:91-97.
4. Ong ME, Mackey KE, Zhang ZC, et al. Mechanical CPR devices compared to manual CPR during out-of-hospital cardiac arrest and ambulance transport: a systematic review. Scand J Trauma Resusc Emerg Med. 2012;20:39.
5. Youngquist ST, Ockerse P, Hartsell S, Stratford C, Taillac P. Mechanical chest compression devices are associated with poor neurological survival in a statewide registry: A propensity score analysis. Resuscitation. 2016;106:102-107.
6. Newberry R, Redman T, Ross E, et al. No Benefit in Neurologic Outcomes of Survivors of Out-of-Hospital Cardiac Arrest with Mechanical Compression Device. Prehosp Emerg Care. 2018;22(3):338-344.
7. Gonzales L, Oyler BK, Hayes JL, et al. Out-of-hospital cardiac arrest outcomes with “pit crew” resuscitation and scripted initiation of mechanical CPR. Am J Emerg Med. 2019;37(5):913-920.
8. Kahn PA, Dhruva SS, Rhee TG, Ross JS. Use of Mechanical Cardiopulmonary Resuscitation Devices for Out-of-Hospital Cardiac Arrest, 2010-2016. JAMA Netw Open. 2019;2(10):e1913298.
9. Wang PL, Brooks SC. Mechanical versus manual chest compressions for cardiac arrest. Cochrane Database Syst Rev. 2018;8:CD007260.