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: Laurie Morrison, Christian Vaillancourt

CoSTR Citation

Nehme Z, Cash R, Dicker B, de Caen A, Perkins G, Dewan M, Dassanayake V, Raffay V, Vaillancourt C, Olasveengen T, Tjelmeland I, Kleinman M, Bray J, on behalf of the International Liaison Committee on Resuscitation (ILCOR) Basic Life Support Task Force. Continuous chest compressions versus standard cardiopulmonary resuscitation for EMS: A systematic review Consensus on Science with Treatment Recommendations [Internet] Brussels, Belgium: International Liaison Committee on Resuscitation (ILCOR) Basic Life Support Task Force, 2024 October 24. 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 led by the Basic Life Support Task Force (Ashoor 2017 112 – PROSPERO CRD42016047811) and conducted by the Knowledge Synthesis Unit at St Michael’s Hospital, Toronto, Canada with involvement of clinical content experts. The review team examined the Ashoor at al. 2017 systematic review and noted a high number of studies that were not identified in the search strategy used. Additionally, the Ashoor review included unadjusted data and some meta-analyses that had considerable heterogeneity.

For the present review, the team revised and re-executed the search strategy from database inception to October 20, 2024. Evidence for adult and pediatric literature was sought and considered by the Basic and Paediatric Life Support Task Forces. Since that time, additional scientific literature was published after the completion of the systematic review and identified by the Basic Life Support Task Force and is described before the justifications and evidence to decision highlights section of this CoSTR. These data were considered when formulating the Treatment Recommendations. The current review also excluded studies reporting unadjusted data and meta-analyses were reconsidered where there was significant heterogeneity between included studies.

Systematic Review

Nehme Z, Cash R, Dicker B, de Caen A, Perkins G, Dewan M, Dassanayake V, Raffay V, Vaillancourt C, Olasveengen T, Tjelmeland I, Kleinman M, Bray J, on behalf of the International Liaison Committee on Resuscitation (ILCOR) Basic Life Support Task Force. Continuous chest compressions versus standard cardiopulmonary resuscitation for EMS: A systematic review [in progress]

PICOST

The PICOST (Population, Intervention, Comparator, Outcome, Study Designs and Timeframe)

Population: Adults and children with out-of-hospital cardiac arrest

Intervention: Continuous chest compressions delivered by emergency medical services (EMS) with or without ventilations

Comparators: Standard CPR, defined as any compression-to-ventilation ratio delivered by EMS. Comparator groups that receive no CPR or compared manual CPR with mechanical CPR were excluded from the review. Studies including automated CPR or any use of mechanical devices were only be included if administered to all treatment arms.

Outcomes: Favourable neurological survival (as measured by cerebral performance category or modified Rankin Score) at discharge or 30-days and at any time interval after 30-days; Survival to discharge or 30 days survival; Survival to any time interval after discharge or 30 days survival; Return of spontaneous circulation (ROSC); Quality of life as measured by any indicator or score.

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. Unpublished studies (e.g., conference abstracts, trial protocols) are excluded. Studies without a comparator group, reviews, and pooled analyses were excluded. Observational studies that only reported unadjusted data were also excluded. All relevant publications in any language are included as long as there was an English abstract.

Timeframe: Literature search was conducted from database inception to October 20, 2024

PROSPERO Registration CRD42024559318

Consensus on Science

A search strategy was executed using Medline and the Cochrane Central Register of Controlled Trials. The broader search identified 11,442 non-duplicate titles, of which 6 studies were deemed relevant and underwent full-text review. Two of the six studies were excluded as they only provided unadjusted estimates of the intervention effect (Kellum 2006 335; Feng 2018 473), including one included in the previous Ashoor 2017 systematic review (Kellum 2006 335). The remaining studies involved a cluster RCT (Nichol 2015 2203) with crossover and three cohort studies including two post-hoc analyses of the earlier cluster RCT (Bobrow 2008 1158; Grunau 2017 e3386; Schmicker 2021 31). All studies originated from North America and three were conducted within the Resuscitation Outcomes Consortium (ROC).

Favourable neurological survival at discharge or 30-days

For the critical outcome of favorable neurological survival at discharge or 30-days, we identified moderate-certainty evidence (downgraded for indirectness and risk of bias) from one cluster RCT (Nichol 2015 2203). In the RCT, 23,711 non-traumatic OHCA patients were randomised to either CCC with asynchronous positive-pressure ventilation (PPV) or standard CPR with a CV ratio of 30:2. Both treatment arms involved the insertion of an advanced airway and continuous chest compressions after the completion of three cycles of CPR of the trial treatment strategy. The trial showed no significant difference in favorable neurological survival (mRS ≤3) at discharge for patients treated with CCC compared with patients randomised to conventional CPR (adjusted risk difference: −0.6 percentage points [95% CI, −1.4 to 0.1]).

Survival to hospital discharge or 30-day survival

For the critical outcome of survival to hospital discharge or 30-day survival, we identified

moderate-certainty evidence (downgraded for indirectness and risk of bias) from one cluster RCT (Nichol 2015 2203) and very-low-certainty evidence (downgraded for risk of bias, imprecision and indirectness) from three cohort studies (Bobrow 2008 1158; Grunau 2017 e3386; Schmicker 2021 31). In the RCT, there was no significant difference in survival to hospital discharge for patients randomised to CCC compared to conventional CPR with a CV ratio of 30:2 (adjusted risk difference: −0.7 percentage points [95% CI, −1.5 to 0.1]) (Nichol 2015 2203). A post-hoc analysis of the Nichol (2017, 2203) cluster RCT restricted to sites in British Colombia also reported no significant difference in survival to hospital discharge for patients randomised to CCC compared to conventional CPR (adjusted risk difference: -0.18 percentage points [95% CI: -2.01, 1.66] (Grunau 2017 e3386).

In a cohort study (Schmicker 2021 31) undertaken within the North American Resuscitation Outcomes Consortium (ROC), patients enrolled into the ROC registry or either the ROC CCC, ALPS or PART clinical trials were eligible for secondary analysis. In this study, 26,810 OHCA patients were classified continuous chest compressions with asynchronous ventilations or conventional CPR (30:2) based on randomisation (for trial patients) or local standard of care (for registry patients). The study showed that CCC was associated with improved survival to hospital discharge when compared to standard CPR (adjusted OR: 1.20 [95% CI: 1.04, 1.38]). However, adherence to the randomised strategy was low. Further analysis showed when adhered to, the intended strategy CCC had significantly lower survival (adjusted OR: 0.72 [95% CI: 0.64, 0.81]), while in patients with the intended strategy, 30:2 had higher survival (adjusted OR: 1.05 [95% CI: 0.90, 1.22]).

In an older cohort study (Bobrow 2008 1158), 886 OHCA patients were examined before and after the implementation of a minimally interrupted cardiac resuscitation protocol (consisting of three initial cycles of 200 uninterrupted chest compressions, passive ventilation via nonrebreather mask, single shocks instead of stacked shocks and immediate resumption of chest compressions post shock). Minimally interrupted cardiac resuscitation was associated with improved survival to hospital discharge (adjusted OR: 3.0 [95% CI: 1.1-8.9]) compared with conventional CPR (including a CV ratio of 15:2, stacked shocks and post-shock rhythm checks).

Return of spontaneous circulation

For the important outcome of return of spontaneous circulation (ROSC), we identified moderate-certainty evidence (downgraded for high-risk of bias) from one cluster RCT (Nichol 2015 2203) and very-low-certainty evidence (downgraded for high-risk of bias and indirectness) from one cohort study (Bobrow 2008 1158). In the RCT (Nichol 2015 2203), there was no significant difference in ROSC for patients randomised to CCC compared to conventional CPR with a CV ratio of 30:2 (adjusted risk difference: −1.1 percentage points [95% CI, −2.4 to 0.1]). In the cohort study (Bobrow 2008 1158), minimally interrupted cardiac resuscitation was not associated with changes in ROSC when compared with conventional CPR (adjusted OR: 1.3 [95% CI: 0.8, 2.0]).

Treatment Recommendations

We recommend that EMS providers perform CPR with 30 compressions to 2 ventilations or continuous chest compressions with positive pressure ventilations delivered without pausing chest compressions until a tracheal tube or supraglottic device has been placed (strong recommendation, moderate-certainty evidence).

Justification and Evidence to Decision Framework Highlights

• Interruptions in chest compressions have been associated with poorer clinical outcomes in observational studies (Christenson 2009 1241). Pauses for ventilations are a significant source of interruptions in chest compressions and may have negative impacts on coronary and aortic blood flow (Berg 2001 2465). Asynchronous positive pressure ventilation may achieve similar oxygenation without compromising chest compression quality.
• This topic was prioritised for review due to the time since the previous systematic review (Ashoor 2017 112) in which a number of additional cohort studies were published on the topic. We identified one large cluster RCT (Nichol 2015 2203) and three cohort studies including two post-hoc analyses of the earlier cluster RCT (Bobrow 2008 1158; Grunau 2017 e3386; Schmicker 2021 31). In the case of the RCT, there the review noted moderate risk of bias from baseline differences in groups, lack of blinding, and potential for contamination in the treatment effect. For the cohort studies, the risk of bias assessment noted serious risk of uncontrolled confounding. All studies were at risk of indirectness due to either a high rate of non-adherence to protocol (Nichol 2015 2203; Grunau 2017 e3386; Schmicker 2021 31) or before-and-after design which included bundled interventions after the introduction of the 2005 Resuscitation Guidelines (Bobrow 2008 1158). Post-hoc analyses of the Nichol (2017, 2203) RCT were also underpowered to detect meaningful differences (Grunau 2017 e3386).
• Based on a large cluster RCT undertaken in North America (Nichol 2015 2203) the likely benefit of CCC on patient outcomes is small. In this RCT, adherence to protocol was low and it is possible that larger differences in patient outcomes exist with greater compliance to CCC strategy. Studies adopting minimally interrupted cardiac resuscitation (Bobrow 2008 1158) have demonstrated larger impacts on patient outcomes, particularly in patients with witnessed shockable OHCA. These studies, however, have typically examined minimally interrupted cardiac resuscitation as a bundle with other resuscitation practice changes and therefore the directness of evidence is uncertain.
• In making these recommendations, the task force noted no high-quality evidence to support the superiority of either CCC or standard CPR for patient outcomes in OHCA. The task force took into consideration that although there was relative homogeneity in the CCC strategies, there was heterogeneity in the use of ventilation strategies, including both asynchronous PPV and passive oxygenation. The adequacy of ventilation were not assessed in any studies, although measures of chest compression quality (e.g. chest compression fraction) were reported.
• The task force also placed a relatively high value on the importance of providing high-quality chest compressions and simplifying resuscitation logistics for EMS providers and noted support for the clinical benefit of bundles of care involving minimally interrupted cardiac resuscitation. There was some evidence to suggest that a CV ratio of 30:2 may be much harder to achieve in practice and would ultimately result in asynchronous ventilations.
• The Task Force removed the 2017 recommendation in support of systems that have implemented minimally interrupted cardiac resuscitation for witnessed shockable OHCA. In doing so, it recognised there was a single retrospective study reporting adjusted estimates for the intervention (Bobrow 2008 1158) with a serious risk of bias from uncontrolled confounding. As the study implemented continuous chest compressions as part of a bundle consisting of other resuscitation practices, it was uncertain if the treatment effect was related to CCC or the other practices introduced.

Knowledge Gaps

Several knowledge gaps were identified in the review of this topic, including:

1. What is the effect of delayed positive pressure ventilation versus 30:2 high-quality CPR?

2. Which elements of minimally interrupted cardiac resuscitation (compressions, ventilations, delayed defibrillation) are most important for patient outcomes?

3. How effective is passive oxygenation during resuscitation?

4. How does adherence to CCC or a CV ratio of 30:2 influence patient outcomes?

EtD: BLS 2221 EMS CCC vs conentional CPR Et D

References

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Kellum MJ, Kennedy KW and Ewy GA. Cardiocerebral resuscitation improves survival of patients with out-of-hospital cardiac arrest. Am J Med. 2006;119:335-40. doi: 10.1016/j.amjmed.2005.11.014.

Nichol G, Leroux B, Wang H, Callaway CW, Sopko G, Weisfeldt M, Stiell I, Morrison LJ, Aufderheide TP, Cheskes S, Christenson J, Kudenchuk P, Vaillancourt C, Rea TD, Idris AH, Colella R, Isaacs M, Straight R, Stephens S, Richardson J, Condle J, Schmicker RH, Egan D, May S, Ornato JP and Investigators ROC. Trial of Continuous or Interrupted Chest Compressions during CPR. N Engl J Med. 2015;373:2203-14. doi: 10.1056/NEJMoa1509139.

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