Tag Archives: EMS

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.

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
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.

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.

Prehospital

What Is The Safest Extrication Method From A Car Crash?

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Today’s post is directed to all those prehospital trauma professionals out there.

Car crashes account for a huge number of injuries worldwide. About 40% of people involved are trapped in the vehicle. And unfortunately, entrapped individuals are much more likely to die.

There are four basic groups (and their category in parentheses) of trapped car occupants:

  • those who can self-extricate or extricate with minimal assistance (self-extrication)
  • individuals who cannot self-extricate due to pain or their psychological response to the event but can extricate with assistance (assisted extrication)
  • people who are advised or choose not to self-extricate due to concern for exacerbating an injury, primarily spine (medically trapped)
  • those who are physically trapped by the wreckage who require disentanglement (disentanglement and rescue)

Prehospital providers have several choices to help extricate patients in the second and third categories: encourage self-extrication, rapid extrication without tools, or traditional extrication, where the vehicle is cut away to allow egress. The fourth category always requires tools for extrication.

Although rescue services try to minimize or mitigate unnecessary patient movement, stuff happens. Large and forceful movement is considered high risk, but smaller movements do occur. This is of particular concern in patients who might have a spine injury.

There have been several recent papers suggesting there might be greater benefits to self-extrication. A group of authors in the UK and South Africa designed a biomechanical study to test these extrication methods in healthy volunteers.

The authors wanted to determine exactly how much movement occurred using the various extrication techniques. The volunteers were fitted with an Inertial Measurement Unit, which measures the orientation of the head, neck, torso, and sacrum in real-time.  The IMU can detect even minimal changes in the orientation of the body. The volunteers were placed in a standard 5-door hatchback sedans that were prepared for each type of extrication, as seen above.

Here are the factoids:

  • A total of 230 extrications were performed for analysis
  • The smallest amount of maximal and total movement of body segments was seen in the self-extrication group
  • The greatest amount of movement was found in the rapid extrication group, with 4x to 5x the movement in the self-extrication group
  • The difference in body movement between the self-extrication group and all others was significant
  • In general, movement increased as extrication techniques progressed from roof removal to B post removal to rapid extrication

The authors concluded that self-extrication resulted in the smallest amount of movement and the fastest extrication time and should be the preferred technique.

Bottom line: This is the first study that specifically evaluated spinal movement occurring with commonly used extrication techniques. Other similar studies have used various measurement techniques, none of which are as precise as this. One potential weakness with this one is that it used healthy volunteers. But obviously, it is not practical to attempt anything like this with real, injured patients. 

Since we know that patients trapped in cars are more likely to die, time is of the essence. This study shows that self-extrication is both fast and safe with respect to spinal movement. The information will assist our prehospital colleagues in making the best decisions possible when faced with patients trapped in their cars.

Reference: Assessing spinal movement during four extrication methods: a biomechanical study using healthy volunteers. Scand J Trauma  open access 30: article 7, 2022.