Category Archives: Prehospital

Prehospital, Resuscitation

Is The Mechanical CPR Device The Next MAST Trousers? Part 3

In my last two posts on this topic, I provided the history of the development of a mechanical CPR device. I also discussed a recent study examining a very large patient population and comparing survival with and without this device. The punchline was that it did not improve 30-day hospital survival or meaningful neurologic survival when used.  Today I’ll look at a few randomized controlled studies and then finish with a Cochrane review on the topic.

The first paper I’ll discuss is the PARAMEDIC trial published in 2014. This study was conducted in non-traumatic arrests in the UK, where ambulance service vehicles were randomly assigned to use a mechanical CPR device versus regular CPR. This intent-to-treat study used 30-day survival as its primary outcome.

A total of 4,471 patients were enrolled with a 1:2 ratio between the mechanical and manual CPR groups. Survival was 6% in the mechanical CPR group and 7% in the manual CPR group. There was no statistically significant difference. There were no serious adverse events in the manual CPR group, but some events did occur in the mechanical group, including chest bruising, lacerations, and blood in the mouth. Mechanical CPR did not confer a survival advantage in this study. 

The next study was the LINC randomized trial published in JAMA, also in 2014. It was a multi-center randomized clinical trial of patients suffering from out-of-hospital cardiac arrest in ambulance services in several European countries. The mechanical CPR recipients also underwent defibrillation if appropriate. The authors measured four-hour survival, survival up to six months, and good neurological outcome.

Four-hour survival was 24% in patients with mechanical CPR and 24% in patients with manual CPR. Survival at 6 months with good neurological outcome was 8.5% vs 7.6%, respectively. Looking at the patients who survived for six months from the flip side, good neurologic outcome was present in 99% of the mechanical CPR group and 94% of the manual group. None of these results were statistically significant. Again, there was no significant improvement in clinical outcomes with the mechanical CPR device. 

Finally, the Cochrane group reviewed eleven existing studies in 2018. They included nearly 13,000 adult patients who suffered either an out-of-hospital or an in-hospital cardiac arrest. Trauma patients were excluded. The overall quality of the studies was judged to be moderate to low due to the considerable risk of bias.

This review concluded that the evidence does not suggest that mechanical CPR devices are superior to conventional therapy. Some of the data reviewed indicate that there may be an increased risk of harm from using this device.

Bottom line: So what does all this mean? Overall, the idea that using a mechanical device to provide continuous, high-quality CPR to improve patient outcomes doesn’t really hold true. Good, old-fashioned manual CPR does just as well. And the mechanical units sold today retail for about $20,000 each. Are they worth the money?

The answer is… maybe. When continuous manual CPR is difficult because few pre-hospital providers are available in the field, automating CPR can be very handy. In some circumstances, such as hypothermia, CPR may need to be continued for an extended period of time. This will burn through numerous humans in a relatively short period of time. It can also be helpful when patients must be moved between different hospital areas or while preparing to place a patient on cardiac bypass. 

Each organization that purchases these units needs to carefully consider how they will use them and how they fit with the resources they have available. Only then can they do the appropriate cost-benefit analysis to see whether it makes sense, given that it seems to have no impact on survival or neurologic outcome. 

And when it comes to CPR in trauma patients, things become very hazy. Major trauma patients are either dying from a fatal brain injury or they are bleeding to death. The use of manual or mechanical CPR has no impact on either of these. 

References:

  1. Mechanical versus manual chest compression for out-of-hospital cardiac arrest (PARAMEDIC): a pragmatic, cluster randomised controlled trial. Lancet. 2015 Mar 14;385(9972):947-55. doi: 10.1016/S0140-6736(14)61886-9. Epub 2014 Nov 16. PMID: 25467566.
  2. 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. doi:10.1001/jama.2013.282538.
  3. Mechanical versus manual chest compressions for cardiac arrest. Cochrane Database Syst Rev. 2018 Aug 20;8(8):CD007260. doi: 10.1002/14651858.CD007260.pub4. PMID: 30125048; PMCID: PMC6953326.
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Prehospital, Resuscitation

Is The Mechanical CPR Device The Next MAST Trousers? Part 2

In my last post, I provided information on the history of the mechanical CPR device. Today I’ll examine the results of a paper published just two weeks ago that studied the rates of favorable neurological survival and overall survival to discharge in patients treated with this device.

A small group of researchers from St. Luke’s Hospital in Kansas City, Emory University in Atlanta, and the University of Texas Southwestern in Dallas performed this study. It was a seven-year, observational cohort study that used the Cardiac Arrest Registry to  Enhance Survival database. This is a prospective, multicenter registry of patients with out-of-hospital cardiac arrest in the U.S. It has a large catchment area of 200 million residents, representing about 60% of the U.S. population.

To evaluate the impact of using a mechanical CPR device for these patients, the agencies evaluated had to have submitted two or more years of data before they started using it. The researchers then evaluated whether introducing the mechanical CPR device was associated with higher survival to discharge or favorable neurological survival.

Here are the factoids:

  • The control group consisted of nearly 52,000 patients, involving 73 EMS agencies. They did not adopt the use of the device during the study period. Simple trends over time were studied.
  • The study group was 49 agencies with 32,000 patients that did begin using the device.
  • Overall favorable neurologic survival ranged from 9.6% to 10.6%, and survival to discharge ranged from 11.1% to 12.0% in the control group. These were not significant differences. It suggests there was no long-term change in these rates due to other factors.
  • In the study group, favorable neurologic survival was 8.9% before mechanical CPR device use, and 8.3% after. This was not a significant difference.
  • Also in the study group, survival to discharge was 11.0% before and 10.0% after. This was not a significant difference.
  • There were no improved outcomes between agencies that used the devices heavily, or if 911-witnessed arrests were included.

The authors concluded that EMS agency rates of favorable neurologic survival and survival to discharge were not any higher at agencies that started using mechanical CPR devices.

Bottom line: This study shows no improvement in two kinds of survival among patients treated by EMS agencies that adopted the mechanical CPR device. It did not evaluate the quality of the CPR applied. However, this is implied in the reason for using this device and the marketing materials provided by the manufacturers. 

This paper provides strike one for using the mechanical CPR device to improve survival. In my next post, I’ll review several smaller randomized clinical trials looking at the impact of these devices. Then I’ll finish up with an analysis of a Cochrane Systematic Review on the benefit of this device. 

Reference: Mechanical CPR Device Use and Cardiac Arrest Survival in EMS Agencies. Circulation. 2026 Aug 11;154(6):532-541. doi: 10.1161/CIRCULATIONAHA.126.079272. Epub 2026 Jun 18. PMID: 42312381; PMCID: PMC13286238.

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Prehospital, Resuscitation

Is The Mechanical CPR Device The Next MAST Trousers? Part 1

It’s very common to see major trauma patients arriving in the trauma bay with a mechanical CPR device strapped to their chest, pounding away. How did this idea start? How effective are they? As you know, anything entrenched in our daily practice to the point that we don’t even question it is fair game for scrutiny in this blog.

I’ve seen these devices used in my trauma patients for about 20 years. They keep getting sleeker and smaller, so I wanted to look at the backstory of these tools.

Why do we even need something like this? Well, there are a few things that we are fairly certain of. First, the survival rate after an out-of-the-hospital cardiac arrest is dismal. Many well-accepted studies estimate survival at about 10%. Second, we also have good data that CPR improves survival in out-of-hospital cardiac arrest. If bystanders start CPR within one minute of arrest, survival to discharge from the hospital increases to 22%. Of course, it decreases as the time interval to start it increases.

We also know that CPR quality can vary based on provider training, fatigue, hand placement, compression depth, and other factors. I’m not aware of any papers that have quantified this. In contrast, mechanical CPR machines provide constant, high-quality compressions and do not get tired. These compressions can be continued indefinitely.

It would seem logical, then, that providing continuous, high-quality CPR is a good thing. But a few of us seasoned trauma professionals recall the good old MAST trousers. These Military Anti-Shock Garments wrapped around the patient’s abdomen and lower extremities and were inflated in patients who were in shock. The idea was that the trousers would push blood from the periphery back into the central circulation, protecting the viscera, brain, and heart. This device was introduced in the 1970s and was used until about the year 2000. You may occasionally find one if you look into old cabinets and closets around your emergency department. They are usually covered by a lot of dust. It seemed like a good idea until the literature showed it didn’t really work. It is now of historical interest only.

Does the literature examining the mechanical CPR device support its use in patients needing CPR? Or is it just going to end up in the dustbin eventually as well? In this post, I’ll talk about the origins of the mechanical CPR device. In the following posts, I’ll look at the most recent literature on how well they work.

The mechanical CPR device was first introduced in 1961. It was a framework designed to fit over a standard hospital stretcher. A source of compressed gas drove a spring-loaded piston onto the patient’s sternum with about 60 lbs. of force. Another group modified this concept by using a portable pneumatic pump to perform compressions.

By 1965, these devices were becoming more “streamlined.” Nachlas and Siedband developed a smaller version that was powered by an oxygen tank, which they believed would eventually fit on an ambulance.

Research on these devices continued through the 1970s, and a few even became commercially available. A set of published standards in 1974 commented on both manual and mechanical chest compression devices. They recommended that only well-trained and experienced personnel operate them. Furthermore, they indicated that their performance was comparable to manual CPR. However, the literature they this was based on was unclear.

These devices dropped off the radar in the 1980s, and interest was rekindled in the 1990s. Ultimately, widespread adoption of commercial devices occurred in the early 2000’s and they enjoy widespread use today.

In my next post, I’ll examine a large study published just last week examining the impact of Mechanical CPR devices on survival after cardiac arrest.

References:

  1. A history of mechanical devices for providing external chest compressions. Resuscitation 2007;73(3):330-336. doi: 10.1016/j.resuscitation.2007.01.002.
  2. Standards for Cardiopulmonary Resuscitation (CPR) and Emergency Cardiac Care (ECC). JAMA 1974;227;(7):833-868. doi:10.1001/jama.227.7.833
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Equipment, Prehospital

Cool EMS Stuff: The Backboard Washer!

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Backboards are made to get messy. Every time your friendly EMS provider brings you a patient, they invariably have to swab it down to give the next patient a reasonably sanitary surface to lie on. But sometimes the boards get downright nasty, and the cleanup job is a major production.

Enter… the backboard washer. I saw one of these for the first time at a Level III hospital in Ohio. Fascinating! Pop the board inside and seven minutes later it’s clean. And I mean really squeaky clean. You may think it looks clean after a good hand wash, but the effluent water coming out of this washer after inserting a hand-cleaned board is still nasty!

These units use standard 100V 20A power and only require a hot water hookup and a drain. They can wash two boards at once.

Hospitals in the know should locate one of these next to a work area for completing EMS paperwork and some free food. What could be better?

Note: I have no financial interest in this company, and I definitely do not have one in my garage.

Reference: Aqua Phase A-8000 spec sheet. Click to download.

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Prehospital

Trauma Patient Mortality In ALS vs BLS Prehospital Transport

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There is a presumption that more education and attainment of more advanced skills lead to greater expertise in just about any field. The same argument holds true for prehospital provider training. Training to be an ALS provider (advanced EMT or paramedic) should add extra value in patient care over and above BLS training (emergency medical responder or EMT).

One way to measure that added value is by comparing trauma patient mortality across those levels of training. Paradoxically, many studies have shown either no benefit or an actual increase in mortality. How does this make sense? Some have speculated that the advanced training leads providers to “stay and play” and use the skills that they have learned. Other possibilities include study design issues (low subject numbers) or failure to consider some unknown variables that impact mortality.

A paper published just this month from Hennepin County Medical Center in Minneapolis examined this phenomenon more closely to determine whether this effect is real or whether other factors are involved. They performed a retrospective study of a nationwide database of prehospital ground transports, selecting records that involved only injured patients. Only patients with documented ALS or BLS providers who were transported to Level I or II trauma centers were included. The ratio of ALS to BLS transports was about 15:1, so propensity matching was performed to create equal groups for comparison.

Here are the factoids:

  • A total of 1,154 matched pairs were available for study,
  • Overall, mortality was significantly lower in the patient group transported by ALS providers
  • Mortality was also significantly lower in older patients (age > 50) and those with mechanisms other than falls
  • There was no statistical difference in patients with falls or in those with prolonged transport times

The authors concluded that more advanced prehospital training is associated with survival. They recognized that there are many factors in the care process that are not captured in the usual databases that may have an impact on survival.

Bottom line: This study was nicely designed and well-executed. It has the largest subject pool of any of the papers published on this topic. It shows that survival is higher when ALS providers transport the patient. But keep in mind that it does not show causality. We don’t know exactly why this is true. It could certainly be the advanced education, but there is still the possibility of other variables that we either haven’t thought of or are not captured in the available databases. But until we know better, we should encourage all EMS providers to up their game, and skill level! 

Reference: Emergency medical services level of training is associated with mortality in trauma patients: A combined prehospital and in-hospital database analysis. Journal of Trauma and Acute Care Surgery ():10.1097/TA.0000000000004540, January 9, 2025.

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