Hanging out with cardiopulmonary researchers effectively imprinted on my psyche that we fail our patients during cardiopulmonary resuscitation in many ways. Unfortunately, too many patients who could have walked out of the hospital after experiencing death don't because of our mistakes in CPR. It's critical to find the resuscitation sweet spot for each patient and to never waver during a CPR event. These are the ways we can kill our patients during cardiopulmonary resuscitation:
Too Slow or Too Fast
The recommended heart rate for cardiopulmonary resuscitation was 60 compressions/minute in 1960. (JAMA 1960;173:1064.) Observational human studies relating compression rate to outcomes, however, have established a sweet spot somewhere between 100 and 120 compressions per minute. (Crit Care Med 2015;43:840.) External chest compressions are the primary intervention performed in cardiopulmonary resuscitation, and not doing them correctly has the greatest impact on the outcome. Without any doubt, compressing too slow or too fast is deadly during CPR.
Too Shallow or Too Deep
Part of the problem with compressing too fast is that the depth of compressions suffers dramatically, and the compressions become too shallow. (Crit Care Med 2015;43:840.) Too deep compressions simply don't appear to add any benefit to resuscitation end-points and may cause unwanted trauma such as broken ribs and increased intracranial pressure (ICP), resulting in reduced cerebral blood flow. Compressions that are too shallow are simply not effective in moving blood into and out of the heart. The AHA recommended compression depth is 2.0 to 2.4 inches or 5 to 6 centimeters. (http://bit.ly/2mZwT3U.) The evidence is strong that the depth of chest compressions makes a difference in survival outcomes. (Circulation 2014;130:1962.)
Too Many or Too Slow
It is almost counterintuitive to think that breathing more frequently for a patient during CPR has the potential to guarantee the patient a trip to the morgue. Ventilating too rapidly or prolonging slower respirations has a dramatic impact on physiology that has been repeated and easily demonstrated in resuscitation laboratories. Positive pressure ventilation in the laboratory increases intrathoracic pressure and intracranial pressure and decreases venous blood return to the right heart.
A decrease in cerebral and coronary artery perfusion pressure occurs during the ventilation process. We need to look at ventilations during cardiopulmonary resuscitation as a necessary evil that they temporarily negate the benefits of our chest compressions while providing oxygen and keeping the airways open for gas exchange. Animal studies unequivocally demonstrate that high ventilation rates can be uniformly lethal in the ventricular fibrillation cardiac arrest model. (Crit Care Med 2004;32[9 Suppl]:S345; Circulation 2004;109:1960.)
Leaning on the Chest
Not allowing full recoil can also be detrimental to effective CPR. It is a subtle and easy not to recognize the error of continuing to put downward pressure and prevent full recoil of the chest. This happens when the rescuer continues to lean on the chest between compressions. Incomplete chest wall recoil or leaning increases ICP and lowers right atrial pressure, decreasing cerebral and coronary perfusion pressures.
Too Many Interruptions
Too many and too long interruptions can negate the benefits of performing spot-on chest compressions. These interruptions ultimately result in the same outcomes as compressing the chest too slowly. No compressions mean no heartbeat.
Giving Up Too Soon
Just how long should we perform cardiopulmonary resuscitation? This partially depends on the patient and his condition. Longer CPR attempts are appropriate from a prehospital perspective, and excellent neurologic recovery is possible for those with the best conditions of shockable rhythms and bystander resuscitation. (Circulation 2016;134:2084.) Hospitalized patients also appeared to benefit from longer CPR, which was associated with greater return of spontaneous circulation and survival to discharge even for the patients in asystole. Efforts to systematically increase the duration of resuscitation could improve survival in this high-risk population. (Lancet 2012;380:1473.)
In reality, the brain is probably a little more resilient than we think. Resuscitation researchers describe porcine research subjects that go about their activities of daily living after prolonged periods of ventricular fibrillation and delayed resuscitation. They also have scores of stories of human patients down for prolonged periods who received effective resuscitation and eventually recovered after prolonged periods of unconsciousness in the intensive care unit. (Resuscitation 2014;85:211.) Reperfusion injury to the brain, however, does happen, and research on how to prevent such injuries is ongoing.
Too Slow Adaptation
It's true that adapting new technologies too soon or before they are adequately vetted with good research is potentially dangerous, but it is also true that good research based on bad CPR can slow the acceptance of potentially useful new resuscitation tools. (Resuscitation 2015;94:106; http://bit.ly/2mZSglK; N Engl J Med 2015;373:2203.) Several decades of work has yielded irrefutable evidence that good things happen to the cerebral perfusion pressure and the coronary perfusion pressure with the impedance threshold device and active compression decompression CPR. (West J Emerg Med 2014;15:803.) And elevating the head simultaneously with the application of an impedance threshold device also clearly improves those physiologic parameters that are associated with better outcomes. (Resuscitation 2016;102:29.) Evidence, finally, is accumulating to validate the decades of work of these resuscitation researchers. (Resuscitation 2017;110:95; Circ J 2016;80:2124.)
Unfortunately, the confounding variables and uncontrolled environment of prehospital cardiac arrest research has slowed the validation and acceptance of important new techniques and technologies as well as something seemingly obvious such as continuous chest compressions during CPR. (Resuscitation 2015;94:106; http://bit.ly/2mZSglK; N Engl J Med 2015;373:2203.)
A commentary by Goodloe, et al., addresses possible options to address the unique challenges of resuscitation research: "This is not to say that high-quality research attempts should not continue, but rather that treatments that appear beneficial to a consensus of resuscitation leaders should not be withheld until benefit is fully demonstrated in primary and confirmatory randomized controlled trials. The unwillingness to adopt new ideas and therapies until they are proven beyond any doubt via randomized clinical trials also holds back progress. Overwhelming evidence is often years in coming, and while we wait, patients die. The context in which resuscitation scientists work is dynamic, complex, and even sometimes chaotic, yet we have made great strides in discovering new processes and technologies that have resulted in better outcomes." (West J Emerg Med 2014;15:803.)
Part of the problem with failure to perform the best CPR possible is that the vast majority of emergency health care providers probably operates with an incomplete understanding of the pathophysiology of cardiac arrest and the physiology of resuscitation. We are much more vulnerable to these mistakes without this complete understanding.
Watch a video showing how conventional CPR works — and doesn’t.
Watch a video with tips for code team organization during CPR.