Happy Thursday (it’s still Thursday on the west coast, that counts). Today I'll be talking a little about the Lund University Cardiopulmonary Assist System, or LUCAS.
The LUCAS is a device that provides mechanical chest compressions, which is used as an alternative to a human compressor. The impetus for the development of this device came when a Norwegian paramedic named Willy Vistung noted that he and his colleagues had difficulties performing high-quality manual compressions while in a speeding ambulance and while transitioning the stretcher. Cardiothoracic surgeon Stig Steen continued development of a mechanical chest compression device after Vistung's passing, with prototype trials starting in Sweden's Lund University in 2000. The first generation of the LUCAS device (which was pneumatic rather than battery-powered like today's LUCAS) entered the market in 2003 in Sweden; the current model of LUCAS 3 has been on the market since 2016. By that time, 45% of all EMS services in the USA had protocols for using mechanical compression devices.
We know that high-quality CPR is the essential component influencing survival in cardiac arrest, and the AHA's five components of high-quality CPR are: minimizing interruptions, maintaining adequate rate, maintaining adequate depth, allowing adequate chest recoil, and ventilating appropriately. In theory, use of a mechanical device such as LUCAS would help with the parameters of rate, depth, and recoil. In the hospital, there are also qualitative benefits in clearing the space at bedside that compressors would occupy, and freeing staff to perform other tasks in the resuscitation (or continue care of other critical patients). The increased quality of compressions seems to be supported by studies involving simulated transport of patients in cardiac arrest, with improvements in rate and depth compared to manual compression. However, does this actually lead to better patient outcomes?
Multiple studies on out-of-hospital cardiac arrest have failed to show that mechanical chest compressions confer any benefit or harm to ROSC or survival. Multiple meta-analyses pooling multiple RCTs, prospective cohort studies, and retrospective studies have added to the growing body of evidence that the general population receives no change in overall outcome whether they have manual or mechanical compressions. As such the 2015 European Resuscitation Council Guidelines for Resuscitation do not recommend routine use of mechanical compression devices such as the LUCAS, but do suggest that their use is reasonable in situations where sustained high-quality manual chest compressions are impractical (such as prolonged resuscitations, transport) or compromise provider safety. The ERC and AHA both speculate that potential benefits of improved chest compression fraction with mechanical compressions may be compromised by delays/interruptions in compression incurred during the transition from manual to mechanical compressions, and recommend that additional training such as simulations/drills be offered by institutions incorporating mechanical compression devices.
Knowing that there's 1) no harm, and 2) potential benefits both quantitatively and qualitatively, I think we should try to maximize good use of LUCAS whenever feasible. For those of you who haven't yet seen or used a LUCAS device, this is what it looks like:
There's a big yellow backboard which will stabilize the device and provide a backstop for the force of the piston. The backboard should be placed on the stretcher before the patient is transferred from the ambulance gurney, because trying to reposition/roll the patient to slide the backboard under after is not ideal. The backboard has a diagram of where it should be placed relative to the patient's chest. The two "legs" of the device should then be locked to the sides of the backboard, and the suction cup at the end of the piston should be lowered over the chest. After turning the device on, the patient's wrists should be strapped to the legs of the device (mainly to ease ergonomics in staff positioning and patient transport). If there are any problems with the device, it should beep and flash some red lights; the most common problems will be those of positioning. Getting all of this done with < 10 seconds of interruptions in chest compressions is a real challenge, and I see the utility in the "pit drills" that the ERC recommends.
Lastly, courtesy of our sim director Dr. Lamberta, we’re aware of a page from Stryker entitled “Myth Busted! The LUCAS device does fit large patients!”. Google it for the actual document. No one will be measuring a patient's body with a ruler during an arrest, but the tech specs of the LUCAS 3 note that it can be used with a sternum height of 6.7 to 11.9 inches, and a chest width of 17.7 inches. Practically-speaking, as long as the patient's chest is not so large that the legs cannot snap in place, or that the suction cup compresses their chest while still in the "start" position, the system can be used. To paraphrase the manufacturer, a large mid-section is not an obstacle to using the LUCAS. For reference, the model in their included illustration is 5'10'' and weighs 320 lbs.
On the other end of the spectrum, LUCAS can be applied in pediatric patients as long as they meet the minimum sternum height of 6.7 inches — that is, enough for the suction cup to be placed on their chest and still compress. The device should alarm if the patient is in fact too small for adequate compressions. My estimation is that the average preadolescent pediatric patients will be smaller or borderline.
References:
https://www.tandfonline.com/doi/full/10.3109/17482941.2012.735675
https://www.sciencedirect.com/science/article/abs/pii/S0736467919311370
https://www.sciencedirect.com/science/article/pii/S0300957215003287
https://cpr.heart.org/-/media/CPR-Files/Resus-Science/High-Quality-CPR/CPR-Statement.pdf
https://www.sciencedirect.com/science/article/abs/pii/S0300957211001225
