Chest compression devices: Are they worth it?
Along with automated external defibrillators and basic airway management, CPR is considered a fundamental component of BLS
Survival from sudden cardiac arrest (SCA) is zero percent if external chest compressions (CPR) are not performed. Since the 1950s, when Dr. Peter Safar first described the modern technique of pushing on the chest to create blood flow, researchers have worked to optimize manual compression depth and rate while trainers have trained millions of people worldwide in CPR.
Along with automated external defibrillators and basic airway management, CPR is considered a fundamental component of basic life support (BLS) in cardiac resuscitation.
From the 1970s to the late 90s, much attention was given to advance life support (ALS). It was thought that medications and ALS procedures such as intubation would help to increase survival rates.
However, in one study after another it became clear that these more complex and complicated techniques were not improving survival rates. It became increasingly obvious that effective BLS in the form of high quality chest compressions was crucial in resuscitation efforts.
In 2005, the American Heart Association recommended that the management of cardiac arrest revolved around minimally interrupted chest compressions of adequate depth and sufficient rate to adequate blood pressure in the cardiovascular system, while ensuring that full recoil off the chest was achieved to allow blood flow through the coronary arteries.
Historically, chest compressions have been delivered manually, with the rescuer kneeling upright next to the victim, using two outstretched arms placed over the sternum, and bending at the hips to create a downward force.
The rescuer returns back to an upright position, releasing all pressure off the chest. This “duty cycle” is repeated at a rate of at least one hundred times per minute, interrupted every 30 compressions to deliver a small volume of air to ventilate the lungs.
There are many challenges to achieving continuous, high quality compressions. First, the rescuer must be of sufficient size and weight in order to generate adequate compressions. It is thought that late middle school children may be the minimum age to learn and deliver CPR.
Second, the training must be simple enough to acquire quickly and retain. Performing CPR is a task that is seldom practiced in real life by the lay public; even professional rescuers perform CPR at a much lower frequency than other procedures such as measuring blood pressure or gaining intravenous access.
Given that mandatory retraining occurs usually on an annual or biannual basis, it becomes difficult to deliver compressions accurately.
Third, fatigue during CPR is a major factor. Studies show that the rescuer’s ability to deliver effective chest compressions decreases significantly in as little as a minute after initiation. It is for this reason that the AHA recommends that rescuers be rotated out of providing compressions every two minutes during a cardiac arrest.
Finally, trying to deliver effective manual chest compressions during patient extrication and transport is extremely difficult. Maintaining body and arm position while in motion is impractical and can harm the rescuer.
Chest compression devices — a panacea?
Given the challenges of trying to perform human-powered CPR, it’s no surprise that biotechnology has been working on mechanically-driven devices that tirelessly deliver accurate chest compressions in virtually any situation.
As early as the 1960s, the “Thumper” made by Michigan Instruments used an oxygen-powered piston on an adjustable arm to deliver compressions.
The Zoll Autopulse delivers chest compressions using a load-distributing band that is wrapped around the victim’s chest and tightened rhythmically by an electrical motor.
Physio Control’s LUCAS can be powered either pneumatically or electrically to compress the chest with a piston in a more compact configuration.
While the design of each device varies, the benefits to the resuscitation team are consistent. Chest compression devices can reduce the number of rescuers needed to perform CPR at a cardiac arrest, since they do not tire.
Properly adjusted, the devices can deliver consistent, uninterrupted compressions throughout the arrest phase. Studies have shown that using chest compression devices does promote coronary blood flow, higher coronary perfusion pressures and can increase the chances of return of spontaneous circulation (ROSC).
Given these findings, it would appear that chest compression devices are superior to providing manual CPR.
Yet large-scale scientific studies have not shown whether these devices are effective in improving the primary measurement of resuscitation success — survival to discharge from hospital.
The costs of the devices are significant, each costing thousands of dollars to purchase. Replacement parts and maintenance can also be costly. It requires significant training and practice to implement each device with minimal interruption to CPR during a cardiac arrest.
At this point, researchers neither recommend nor discount the routine use of mechanical CPR devices in cardiac arrest; more research is needed. It is clear that the potential benefits to the use of such devices are significant.
Better training and practice in deploying chest compression devices may help improve arrest outcomes. As biotech companies refine their products and optimize their use, the benefit to patient survival to discharge will become more evident.
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