Conflict of Interest Declaration
The ILCOR Continuous Evidence Evaluation process is guided by a rigorous ILCOR Conflict of Interest policy. The following Task Force members and other authors were recused from the discussion as they declared a conflict of interest: none applicable
The following Task Force members and other authors declared an intellectual conflict of interest and this was acknowledged and managed by the Task Force Chairs and Conflict of Interest committees: Olasveengen TM, Morrison L, Vaillancourt C.
CoSTR Citation
Smyth MA, Nishiyama C, Singh B, Olasveengen TM, Bray JE on behalf of the International Liaison Committee on Resuscitation Basic Life Support Task Force. Duration of CPR cycles Consensus on Science with Treatment Recommendations [Internet] Brussels, Belgium: International Liaison Committee on Resuscitation (ILCOR) Basic Life Support Task Force, 2024. Available from: http://ilcor.org
Methodological Preamble and Link to Published Systematic Review
The continuous evidence evaluation process for the production of Consensus on Science with Treatment Recommendations (CoSTR) started with a systematic review conducted by Michael Smyth, Chika Nishiyama and Baljit Singh supported by Thresa Olasveengen and Janet Bray. The evidence was independently reviewed by M Smyth, C Nishiyama and B Singh and subsequently considered by the Basic Life Support Task Force. These data were considered when formulating the Evidence to Decision Framework and subsequent Treatment Recommendation.
Definitions used:
Adults = > 18 years (however some papers might include > 16 years)
Cardiac arrest = Unconscious person not breathing normally
Any setting = in-hospital and out-of-hospital setting
CPR cycle = interval between pausing chest compressions to assess the cardiac rhythm (expressed in time or number of compressions)
Systematic Review
No systematic review publication associated with this update.
PICOST
The PICOST (Population, Intervention, Comparator, Outcome, Study Designs and Timeframe)
Population: Adults and children in any setting (in-hospital or out-of-hospital) with cardiac arrest
Intervention: Does pausing chest compressions at another interval
Comparators: Compared with pausing chest compressions every two minutes to assess the cardiac rhythm
Outcomes: Critical: Survival with favourable neurological outcome at hospital discharge or 30-days; Survival at hospital discharge or 30 days. Important: Return of spontaneous circulation (ROSC); Coronary perfusion pressure, Cardiac output.
Study Designs: Randomized controlled trials (RCTs) and non-randomized studies (non-randomized controlled trials, interrupted time series, controlled before-and-after studies, cohort studies) are eligible for inclusion. Case series were included if they contained ≥ 5 cases. Unpublished studies (e.g., conference abstracts, trial protocols), animal studies, mathematical models, simulation and mannikin studies, algorithm studies with no outcome data were excluded.
Timeframe: All relevant publications in any language were included as long as there was an English abstract. Search dates were restricted to 01 September 2014 (date of most recent systematic review) up to September 22nd, 2024
Consensus on Science
Searches identified 964 manuscripts, title and abstract screening resulted in 7 as potentially relevant. Following full-text review, 5 studies were excluded (these manuscripts addressed either continuous compressions or compression fraction which are addressed in alternate PICOST questions), and two studies were relevant. Of the two relevant manuscripts, 1 was already included in the 2015 ILCOR review (Nordseth 2014 75) and the other was the 2015 systematic review publication from ILCOR published in Resusciation (Reynolds 2015 38). Consequently, no new data were identified by the literature search. It should be noted that the evidence is dominated by studies addressing the initiation of resuscitation rather than the whole resuscitation period, with most studies covering the period of CPR to first shock or circulation assessment (pulse check or rhythm assessment). Furthermore, many studies were conducted before the current ratio of 30:2. The risk of bias assessment was updated using ROB-2 and Robins-I and studies.
The pre-existing summary of data is presented below.
3 min vs 1 min
In the Wik study,(Wik 2003 1389) the control group (1 min group) included patients that received immediate defibrillation (up to three stacked shocks) for VF/VT followed by 1 min of CPR patients in refractory VF/VT, and 3 minutes of CPR for patients that were in non-shockable rhythms following initial 1-3 shocks. The intervention group (3 min group) included patients that received immediate defibrillation (up to three stacked shocks) for VF/VT followed by 3 minutes of CPR regardless of post-shock rhythm.
For the critical outcome of survival to hospital discharge with favourable neurological outcome (O), we identified very low-certainty evidence (downgraded for risk of bias and imprecision) from 1 RCT (Wik 2003 1389) enrolling 200 adult out-of-hospital cardiac arrests (P), which observed no benefit from intervention (I) when compared to control treatment (C) (RR, 1.68; 95%CI, 0.85–3.32; P = 0.13; absolute risk reduction [ARR], -7.77%; 95% CI, −17.70% to 2.41%, or 78 more patients/1000 survived with the intervention [95% CI, 18 fewer patients/1000 to 230 more patients/1000 survived with the intervention])
For the critical outcome of survival to hospital discharge (O), we identified very low-certainty evidence (downgraded for risk of bias and imprecision) from 1 RCT (Wik 2003 1389)enrolling 200 adult out-of-hospital cardiac arrests (P), which observed no benefit from intervention (I) when compared to control treatment (C) (RR, 1.52; 95%CI, 0.83–2.77; P = 0.17; absolute risk reduction [ARR], -7.53%; 95% CI, −18.09% to 3.35%, or 60 more patients/1000 survived with the intervention [95% CI, 19 fewer patients/1000 to 203 more patients/1000 survived with the intervention])
For the important outcome of return of spontaneous circulation (O), we identified low-certainty evidence (downgraded for risk of bias and imprecision) from 1 RCT (Wik 2003 1389) enrolling 200 adult out-of-hospital cardiac arrests (P), which observed no benefit from intervention (I) when compared to control treatment (C) (RR, 1.22; 95%CI, 0.92–1.50; P = 0.16; absolute risk reduction [ARR], -9.94%; 95% CI, −23.22% to 3.87%, or 25 more patients/1000 survived with the intervention [95% CI, 9 fewer patients/1000 to 69 more patients/1000 survived with the intervention])
1 min vs 2 min
In the Baker study,(Baker 2008 424) the control group (2 min group) included patients that were enrolled in a separate RCT after implementation of new guidelines introducing single shocks, 30:2 CPR and 2 min CPR cycles between defibrillations. The intervention group (1 min group) included patients that were enrolled in a separate RCT before implementation of new guidelines, and were therefore treated with stacked shocks (up to three in refractory VF/VT), 15:2 CPR and 1 min CPR cycles between defibrillations sequences. The change in guidelines happened 380 days into a 2 year long trial.
For the critical outcome of survival to hospital discharge (O), we have identified very low-certainty evidence (downgraded for risk of bias, indirectness and imprecision) from 1 RCT (Baker 2008 424) enrolling 202 adult out-of-hospital cardiac arrests (P), which showed no benefit from intervention (I) when compared to control treatment (C) (RR, 0.49; 95%CI, 0.23–1.06; P = 0.06; absolute risk reduction [ARR], -9.23%; 95% CI, −0.49% to 18.45%, or 58 fewer patients/1000 survived with the intervention [95% CI, 88 fewer patients/1000 to 7 more patients/1000 survived with the intervention])
For the important outcome of return of spontaneous circulation (O), we have identified very low-certainty evidence (downgraded for risk of bias, indirectness and imprecision) from 1 RCT (Baker 2008 424) enrolling 202 adult out-of-hospital cardiac arrests (P), which showed no benefit from intervention (I) when compared to control treatment (C) (RR, 0.95; 95%CI, 0.73–1.24; P = 0.71; absolute risk reduction [ARR], −2.60%; 95% CI, −11.04% to 16.113%, or 6 fewer patients/1000 survived with the intervention [95% CI, 31 fewer patients/1000 to 27 more patients/1000 survived with the intervention]).
Treatment Recommendations
We suggest rescuers should assess the cardiac rhythm every two minutes (weak recommendation, very-low certainty of evidence).
Justification and Evidence to Decision Framework Highlights
This topic was prioritised for review by the BLS Task Force as it had not been formally updated since 2015, at which time no direct evidence addressing this topic was identified. This remains the case in 2024. Previous systematic reviews identified two studies (Wik 2003 1389, Baker 2008 424) which indirectly included comparisons between groups with different CPR durations, each had significant limitations. Both studies were designed to primarily address the question of CPR vs defibrillation first, and the certainty of evidence derived from these studies to support recommendations on the optimal duration of CPR before a scheduled rhythm analysis was seriously confounded and therefore low.
A further 2014 study (Nordseth 2014 75) sought to establish the optimal time to first rhythm check among patients presenting in PEA or asystole. The study measured time to conversion to shockable rhythm or time to ROSC. The authors suggested that the first rhythm check might be delayed until 4 minutes for patients presenting in PEA and 6-8 minutes for patients presenting in asystole. However, the authors did not report an effect estimate to reliably inform this question. Their conclusions were based upon their observation that conversion of PEA/asystole to shockable rhythm or ROSC took longer than 2 minutes. Furthermore, they noted that the likelihood of conversion declined with each 2-minute cycle.
In making the suggestion to pause chest compressions every two minutes to assess cardiac rhythm, we placed a high value on being consistent with previous recommendations and the absence of any convincing evidence indicating potential benefit from changing to CPR cycles of a different duration. The BLS Task Force acknowledges that every change in guidelines comes with a significant risk and cost as CPR educators and providers are asked to change current practices and implement new treatment strategies for complex and high-stress medical emergencies.
Knowledge Gaps
Current knowledge gaps include but are not limited to:
- Does the optimal CPR interval between rhythm analyses differ for patients with different initial cardiac rhythms?
- Does the duration between collapse and EMS arrival affect the optimal interval?
- Do different intervals interfere with the overriding goal of minimising interruptions in chest compressions?
- What is the relationship between rescuer fatigue, chest compression quality, and the optimal interval?
EtD: BLS 2212 Duration of CPR cycles Et D
References
Baker, P. W., J. Conway, C. Cotton, D. T. Ashby, J. Smyth, R. J. Woodman and H. Grantham (2008). "Defibrillation or cardiopulmonary resuscitation first for patients with out-of-hospital cardiac arrests found by paramedics to be in ventricular fibrillation? A randomised control trial." Resuscitation 79(3): 424.
Nordseth, T., D. P. Edelson, D. Bergum, T. M. Olasveengen, T. Eftestøl, R. Wiseth, J. T. Kvaløy, B. S. Abella and E. Skogvoll (2014). "Optimal loop duration during the provision of in-hospital advanced life support (ALS) to patients with an initial non-shockable rhythm." Resuscitation 85(1): 75.
Reynolds, J. C., V. Raffay, E. Lang, P. T. Morley and K. Nation (2015). "When should chest compressions be paused to analyze the cardiac rhythm? A systematic review and meta-analysis." Resuscitation 97: 38.
Wik, L., T. B. Hansen, F. Fylling, T. Steen, P. Vaagenes, B. H. Auestad and P. A. Steen (2003). "Delaying defibrillation to give basic cardiopulmonary resuscitation to patients with out-of-hospital ventricular fibrillation: a randomized trial." Jama 289(11): 1389.