A combination of 107 chest compressions per minute at a depth of 4.7 centimeters is the optimal CCR-CCD (chest compression rate-chest compression depth) ratio for survival after an out-of-hospital cardiac arrest, researchers reported August 14 in JAMA Cardiology.
The purpose of Sue Duval, PhD, et al.’s study was to identify the ideal CCR-CCD combo for victims of out-of-hospital cardiac arrest, whose shot at survival hovers somewhere around 10%. It’s a delicate balance to strike—compressions that are too fast won’t allow for enough ventricular filling between compressions, and compressions that are too deep risk major thoracic injury.
Duval, of the University of Minnesota Medical School, and colleagues said clinical reports have identified better neurologic outcomes and survival in cardiac arrest victims treated within “favorable” ranges of CCR and CCD, but those ranges were independently identified for each study. Clinical guidelines recommend a CCR of between 100 and 120 compressions per minute at a depth of 5 to 6 centimeters.
“Data are still lacking with respect to specifically identifying the optimal combination of CCR and CCD and whether the same CCR-CCD target combination should be applied to all patients irrespective of sex, age, presenting cardiac rhythm or CPR adjunct use,” the authors wrote in JAMA. “Knowing, monitoring and confirming target CCR-CCD combinations would not only optimize treatment but also improve the study design and reliability of clinical studies.”
Duval’s team used data collected between June of 2007 and November of 2009 from a National Institutes of Health clinical trials network to study 3,643 patients who experienced out-of-hospital cardiac arrest and whose CCR and CCD values had been recorded at the time. Of the study pool, nearly 65% were men and the mean age was 67.5 years old.
The authors identified 107 compressions per minute at a depth of 4.7 centimeters as the optimum CCR-CCD combination, defined by functionally favorable survival. They found that when CPR was performed within 20% of that value, survival probability was 44% higher (6% in patients who received the combo vs. 4.3% who didn’t). The combination remained optimal even after adjustment for age, sex, presenting cardiac rhythm or CPR adjunct use.
When a CPR device was used, victims were more likely to survive a cardiac arrest, though that benefit was dependent on being near the target CCR-CCD combination.
Asking how Duval et al.’s findings could be validated, David C. Cone, MD, in a related editorial suggested the team try to replicate their results in patients managed with mechanical CPR devices, since those are “fairly exact and consistent” in their compression rate and depth. Still, Cone, of Yale University, said it’s unknown if the same CCR-CCD combination would even be optimal for mechanically managed patients, since their machines don’t necessarily mimic human rescuers.
“Given that the 20% window around the identified optimal combination largely overlaps with current international recommendations for rate and depth, emergency medical services systems that opt to implement the proposed combination now, prior to validation, are likely acting reasonably,” he wrote. “While the findings of Duval et al. are unlikely to lead to a change in international CPR guidelines on their own, they do support the simplest CPR mantra: push hard, push fast and do not stop.”