So often we apply qualitative dichotomies to quantitative differences even when questionable clinical distinction exists. Such is the case with the general interpretation of a recent article published in Resuscitation.
Huis in ’t Veld et al examined video recordings of real life Emergency Department resuscitations of patients in cardiac arrest (1). Over a one year period 23 patients were enrolled. These patients presented to the Emergency Department in cardiac arrest and were treated in one of three resuscitation bays with video recording capabilities. The authors examined the video recordings and documented the time elapsed during each pulse check. They then noted the time elapsed during each pulse check and classified them according to whether they did or did not utilize bedside ultrasound.
Not surprisingly, pulse checks which utilized US took significantly longer than those without bedside US employed, 21.0 seconds vs 13.0 seconds, respectively. This is a clear and simple observation. Bedside US increases the time spent off the chest. The clinical consequences of such an observation are far more complex.
The conclusion that US increases the length of a pulse check assumes that all pulse checks are equal, which as anyone who has been part of a resuscitation realizes is not the case.The authors examined 123 pulse checks in 23 patients, with each patient often receiving multiple pulse checks both with and without US. Resuscitations are dynamic events, simultaneously balancing the necessity of identifying correctable etiologies and providing adequate circulatory support. There are moments in a code when diagnostic uncertainty, or therapeutic necessity require longer moments of circulatory compromise. Likewise, towards the end of the code when the objective shifts towards prognosis, the importance of circulatory support is once again supplanted by alternative goals. So to understand the value of any procedure we have to understand its utility and the cost of stopping compressions.
It is undeniable that early chest compressions increase the duration of time a patient remains in a shockable rhythm, the chances of successful defibrillation, and neurologically intact survival. And while we know chest compressions are important, how fast, how deep or how frequent we should be performing them is far less certain. The AHA's recommendation to perform chest compressions at a rate of 100 to 120 compressions per minute is based off a number of reanalyses of prospective cohorts of OHCA patients (2). The most commonly cited is by Idris et al published in Critical Care Medicine in 2015 (3). Using data from the ROC-PRIME trial, the authors examined compression rates during the first 5 minutes after EMS’s arrival to see how varying rates might affect outcomes. The authors noted in their unadjusted analysis that the optimal rate for survival was between 100-120 compressions per minute. While this benefit was seen when compared to patients who received a rate of 120-140 or greater than 140, it did not appear better than compressing at a rate of less than 80 compressions per minute. When the authors controlled for patients’ sex, age, bystander-witnessed arrest, EMS-witnessed arrest, bystander CPR, location, initial rhythm, and site location this apparent benefit disappeared. It was only after performing an additional logistical regression analysis that controlled for compression depth and fraction, that a rate of 100-120 again appeared to be associated with improved survival when compared to 80-99 and 120-140. This benefit was not present when compared to <80 or >140 compressions per minute.
When Jost et al conducted an RCT comparing standard CPR to a protocol that optimized CPR performance, the authors found no difference in survival (4). Nichols et al published the results of their 26,148 patient RCT comparing continuous chest compressions to traditional CPR, and found no survival benefit to continuous chest compressions (5). All 5 RCTs comparing standard manual CPR to mCPR failed to demonstrate a benefit in patient outcomes (6,7,8,9,10). In fact, virtually no high-quality RCT has ever found a survival benefit to optimizing perfusion by improving the quality of CPR. And despite this negative evidence we dogmatically insist upon a rate that was derived from a retrospective analysis of the initial five minutes of arrest, that required multiple statistical manipulations to demonstrate a benefit.
The same can be said for the data supporting chest compression fraction (CCF). While CCF is an important marker for coronary perfusion pressure and eventual ROSC, it is not absolute. In fact, the data on the association between CCF and survival is inconsistent at best.
While a number of observational trials have demonstrated a positive correlation between survival and CCF, recent studies have found the opposite (11,12). Cheskes et al found that in patients with the highest compression fraction (>80%), survival was lowest (13). To reconcile these inconsistencies Wik et al sought to determine the true importance of CCF (14). Using the CIRC data set, they examined the subset of patients who received manual chest compressions and extracted the CCF. The authors performed a regression analysis to determine if there was an association between CCF and age, duration of resuscitative efforts, and number of defibrillations.
A total of 1,997 cases had complete data and were used for this secondary analysis. In the unadjusted analysis, the authors found that increasing CCF was associated with decreased survival. It was only when the authors controlled all the factors that influence outcomes that they found a concordant rate of survival and CCF. The authors hypothesized that these contradictory findings were likely due to the fact that there are important prognostic factors that directly affect CCF in a negative fashion, but improved overall survival. Most notable is the presence of a shockable rhythm. Pauses will inherently be longer in patients who require defibrillation than those that are in a PEA or asystole reducing CCF, while markedly improving outcomes.
And so we are left with competing priorities. Stuck between diagnostic urgency and therapeutic necessity. As always this is not a decision that can be protocolized in a dogmatic fashion, rather is a judgment made at the bedside, for that patient, at that moment. Which is more valuable, the diagnostic information garnered from the bedside US, or the hemodynamic support provided by the ongoing chest compressions? In the patient with a shockable rhythm, bedside US provides no added benefit to rapid defibrillation. But for the patient with PEA or asystole, where the likelihood of survival with chest compressions alone is minimal, these extra seconds spent in search of a correctable etiology may in fact be life saving.
- Huis in ’t Veld MA, et al. Ultrasound use during cardiopulmonary resuscitation is associated with delays in chest compressions. Resuscitation (2017)
- Idris AH, Guffey Det al Resuscitation Outcomes Consortium Investigators. Chest compression rates and survival following out-of-hospital cardiac arrest. Crit Care Med. 2015;43:840–848.
- Jost D, Degrange H, Verret C, Hersan O, Banville IL, Chapman FW, Lank P, Petit JL, Fuilla C, Migliani R, Carpentier JP, DEFI 2005 Work Group: DEFI 2005. a randomized controlled trial of the effect of automated external defibrillator cardiopulmonary resuscitation protocol on outcome from out-of-hospital cardiac arrest. Circulation. 121: 1614-1622. 10.1161/CIRCULATIONAHA.109.878389.
- Nichol G, Leroux B, Wang H, et al. Trial of Continuous or Interrupted Chest Compressions during CPR. N Engl J Med. 2015;373(23):2203-14.
- Hallstrom A, Rea TD, Sayre MR, et al. Manual chest compression vs use of an automated chest compression device during resuscitation following out-of-hospital cardiac arrest: a randomized trial. JAMA. 2006;295(22):2620-8.
- Smekal D, Johansson J, Huzevka T, Rubertsson S. A pilot study of mechanical chest compressions with the LUCAS™ device in cardiopulmonary resuscitation. Resuscitation. 2011;82(6):702-6.
- Rubertsson S, Lindgren E, Smekal D, et al. Mechanical chest compressions and simultaneous defibrillation vs conventional cardiopulmonary resuscitation in out-of-hospital cardiac arrest: the LINC randomized trial. JAMA. 2014;311(1):53-61.
- Wik L, Olsen JA, Persse D, et al. Manual vs. integrated automatic load-distributing band CPR with equal survival after out of hospital cardiac arrest. The randomized CIRC trial. Resuscitation. 2014;85(6):741-8.
- Perkins GD, Lall R, Quinn T, et al. Mechanical versus manual chest compression for out-of-hospital cardiac arrest (PARAMEDIC): a pragmatic, cluster randomised controlled trial. Lancet. 2015;385(9972):947-55.
- Vaillancourt C, Everson-Stewart S, Christenson J, et al. The impact of increased chest compression fraction on return of spontaneous circulation for out of hospital cardiac arrest patients not in ventricular fibrillation. Resuscitation. 2011;82(12):1501-1507.
- Christenson J, Andrusiek D, Everson-Stewart S, et al. Chest compression fraction determines survival in patients with out-of-hospital ventricular fibrillation. Circulation. 2009;120(13):1241-1247.
- Cheskes S, Schmicker RH, Rea T, et al. Chest compression fraction: A time dependent variable of survival in shockable out-of-hospital cardiac arrest. Resuscitation. 2015;97:129-35.
- Wik L, Olsen JA, Persse D, et al. Why do some studies find that CPR fraction is not a predictor of survival?. Resuscitation. 2016;104:59-62.