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