The prevalence and magnitude of common CPR problems, their probable root causes, and strategies for the reduction or elimination of these problems

The AHA guidelines[1] for cardiovascular resuscitation require that the victim be placed on their back on a hard flat surface; that the victim’s chest be compressed between five and six centimeters (2.0 to 2.4 inches) without more than a 10 second interruption every two minutes. The rescuer must remove almost all the compression force from the victim’s chest at the top of the full-recoil upstroke. The rate of compression must remain between 100 and 120 compressions per minutes. Additionally, the victim should be ventilated at a rate between eight and ten ventilations per minute, once intubated.


Introduction
The AHA guidelines [1] for cardiovascular resuscitation require that the victim be placed on their back on a hard flat surface; that the victim's chest be compressed between five and six centimeters (2.0 to 2.4 inches) without more than a 10 second interruption every two minutes. The rescuer must remove almost all the compression force from the victim's chest at the top of the full-recoil upstroke. The rate of compression must remain between 100 and 120 compressions per minutes. Additionally, the victim should be ventilated at a rate between eight and ten ventilations per minute, once intubated.
The measurements made during the trial captured the rate of chest compression, the amount of force generated, the extent each subject failed to achieve full recoil, and the length and number of interruptions. The force data was used in conjunction with the Philips chest stiffness data to calculate the percentage of the adult population on whom that test subject could perform GC3's. Measurement of the depth achieved on a standard manikin doesn't reveal much about the capability of a test subject other than a yes / no result that is only valid for their performance on adults whose chest stiffness is equal to or less than the manikin used. That is why the "can they do it?" question was expanded to include "…and on what percentage of the adult population?"

Materials/Methods
A Force Meter ( Figures 1A and 1B) was used to measure the forcegeneration capability of each subject tested and to measure leaning, rate, and interruptions. The Force Meter consists of a PC, a plastic hollow column, a top cap, a heavy-duty spring, and a load cell, connected to the PC. The PC runs software sold by the load cell vendor.
The detail of a two-segment trial on the Force Meter screen ( Figure  2) shows two trials separated by a coaching session. Note that the left segment trace does not get down to zero pounds. In other words, the subject was leaning until coached. During a subsequent re-testing of a sub-set of the cohort, it was demonstrated that the effect of the coaching was not lasting.
The distribution of adult chest stiffness reported by the Philips chest stiffness data enabled the authors to construct Figure 3  All forty-four subjects were either EMTs or Paramedics with an Emergency Medical System at the time of the trial. The force trial was limited to 60 compressions to ensure that we were measuring the subject's best performance, not one modulated by the subject's stamina. The results we observed represent the best the subjects could produce.
The data gathered during the trial appears in Table 1. These data show (from left-to-right) a number unique to each participant, a reference number that appeared on the data acquisition form, the compression rate during the 60 compression trial, whether or not the rate was within the guideline limits (100-120 per minute), whether the subject was within the 0 to 1.5 pound "safe" limit for nearly all the compressions, whether there were any interruptions (there were none), the maximum number of pounds of leaning observed, and the minimum number of pounds observed.

1.
Chest compression performed by these subjects was convincingly flawed for multiple reasons.

2.
Many EMS personnel and bystanders are physically not able to compress a victim's chest to guideline depth. The root cause is due to a misconception among many that one's ability to compress a chest to guideline depth depends upon strength. It does not. The force a person applies to a chest to achieve GC3's is dependent upon four factors: The stiffness of the victim's chest, the weight and weight distribution of the rescuer, and the compression method used. Some EMS personnel could not perform GC3's on even an average stiffness chest. (e.g. subjects 23 and 32.)

3.
Many EMS personnel compress at too fast a rate and leave too much weight on the victim's sternum at the top of a (supposedly) full recoil stroke. The root cause is an inability to self-regulate in most EMTs and Paramedics tested. During this trial, residual force less then    1.5 pounds was not counted as leaning, because the negative effect on the victim of 1.5 pounds of leaning is almost non-existent. (See figure 4 [4].)The vast majority (more than four out of five) of the test subjects failed to perform GC3's due to excessive rate. Five-eighths failed to perform CG3's due to "leaning" (the application of excessive residual force on the sternum.) Only one of the 44 subjects was able to control leaning and rate within guidelines.

4.
When a sub-set of the cohort was tested two to three months after the trial, it became clear that the effect of verbal coaching that was mostly effective in reducing leaning at the time of the original trial did not last. This rules out coaching in a training session as a solution.

5.
When the ambulance crew gets to an arrested victim, the victim either has or has not been receiving GC3's from the time of the arrest until the hands-on arrival of the ambulance crew. The root causes are both the lack of training in a method that most bystanders can perform for ten minutes and the lack of alternative resources such as a personal AED. Many witnesses to a cardiac arrest are about the same age as the victim and hence sometimes are burdened with arthritis problems and might not be able to get the victim onto their back on a hard, flat surface -a requirement for effective CPR. Recent work has demonstrated that the use of heel compression by a bystander quadruples the number of rescuers that can perform GC3's for ten minutes. Trenkamp, Perez 2015 [2].