Starting CPR (ABC vs. CAB) (BLS): Systematic Review

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This CoSTR is a draft version prepared by ILCOR, with the purpose to allow the public to comment and is labeled “Draft for Public Comment". The comments will be considered by ILCOR. The next version will be labelled “draft" to comply with copyright rules of journals. The final COSTR will be published on this website once a summary article has been published in a scientific Journal and labeled as “final”.

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: (none applicable)

CoSTR Citation

Considine J, Mancini ME, Morley P, Avis S, Brooks S, Castren M, Chung S, Escalante R, Kudenchuk P, Nishiyama C, Perkins G, Ristagno G, Semeraro F, Smyth M, Olasveengen TM - on behalf of the International Liaison Committee on Resuscitation Basic Life Support Task Force.

Starting CPR (ABC vs. CAB) for Cardiac Arrest in Adults and Children Consensus on Science with Treatment Recommendations [Internet] Brussels, Belgium: International Liaison Committee on Resuscitation (ILCOR) Basic Life Support Task Force, 2019 Dec 29th. Available from:

Methodological Preamble

The continuous evidence evaluation process for the production of Consensus on Science with Treatment Recommendations (CoSTR) started with a systematic review of basic life support conducted by Julie Considine (BLS Task Force member), with involvement of clinical content experts (Julie Considine and Mary Elisabeth Mancini). Evidence for adult and pediatric literature was sought and considered by the Basic Life Support Adult Task Force and the Pediatric Task Force groups respectively.

There is ongoing debate in the scientific literature regarding the merits of commencing resuscitation with chest compressions prior to ventilations. Internationally, most adult BLS guidelines commence chest compressions prior to ventilations however there is variability in paediatrics and aquatic rescue with different approaches in various jurisdictions.


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

Population: Among adults and children who are in cardiac arrest in any setting

Intervention: Commencing CPR beginning with compressions first (30:2)

Comparators: CPR beginning with ventilation first (2:30)

Outcomes: Survival with favourable neurological / functional outcome at discharge, 30 days, 60 days, 180 days AND/OR 1 year; survival only at discharge, 30 days, 60 days, 180 days AND/OR 1 year; and ROSC.

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.

Exclusion criteria: Unpublished studies (e.g., conference abstracts, trial protocols) and animal studies are excluded. Studies of dispatcher or telephone assisted CPR.

Timeframe: All languages were included as long as there is an English abstract. Literature search was updated Sept 2019.

Consensus on Science

This current systematic review did not identify any additional human or manikin studies published since the 2015 ILCOR systematic review. The state of published evidence remains 4 manikin studies: 1 randomized study (Marsch 2013 w13856) focused on adult resuscitation, 1 randomized study focused on pediatric resuscitation, (Lubrano 2012 1473) and 2 observational studies focused on adult resuscitation (Kobayashi 2008 333, Sekiguchi 2013 1248).

For the important outcomes of time to commencement of chest compressions (RCT: n=1, Lubrano 2012 1473, observational: n=2, Kobayashi 2008 333, Sekiguchi 2013 1248), time to commencement of rescue breaths (RCT: n=2, Lubrano 2012 1473, Marsch 2013 w13856) and time to completion of first CPR cycle (RCT: n=1, Marsch 2013 w13856), we identified only manikin studies. The overall certainty of evidence was rated as very low for all outcomes primarily due to a very serious risk of bias and indirectness. The individual observational studies were all at a critical risk of bias due to confounding and the randomized controlled trials were all at critical risk of bias due to lack of blinding. Because of this and a high degree of heterogeneity, no meta-analyses could be performed and individual studies are difficult to interpret.

For the important outcomes of time to commencement of chest compressions, we identified very-low-certainty evidence from 1 randomized manikin study (Lubrano 2012 1473) representing 155 two-person teams and very-low-certainty evidence from 2 observational manikin studies (Kobayashi 2008 333, Sekiguchi 2013 1248) representing 40 individual rescuers (Sekiguchi 2013 1248) and 33 six-person teams. (Kobayashi 2008 333) All studies were downgraded due to risk of bias. All studies found that C-A-B decreased the time to commencement of chest compression. The randomized trial found a statistically significant 24.13-second difference (P < 0.05) in favor of C-A-B. (Lubrano 2012 1473) The observational studies found statistically significant decreases of 20.6 s (P < 0.001) (Sekiguchi 2013 1248) and 26 s (P < 0.001), (Kobayashi 2008 333) respectively.

For the important outcome of time to commencement of rescue breaths, we identified very-low-certainty evidence from 2 randomized manikin studies (Marsch 2013 w13856, Lubrano 2012 1473) representing 210 two-person teams. Both studies were downgraded due to risk of bias. Lubrano (Lubrano 2012 1473) found a statistically significant 3.53-s difference (P < 0.05) in favorof C-A-B during a respiratory arrest scenario; however, in a cardiac arrest scenario, A-B-C decreased the time to commencement of rescue breaths by 5.74 s (P < 0.05). (Marsch 2013 w13856) Marsch found that C-A-B decreased time to commencement of rescue breaths by 5 s (P = 0.003). The clinical significance of these differences is unknown. (Marsch 2013 w13856)

For the important outcome of time to completion of first CPR cycle (30 chest compressions and 2 rescue breaths), we identified low-certainty evidence (downgraded for risk of bias) from 1 randomized manikin study (Marsch 2013 w13856) representing 55 two-person teams. Marsch (Marsch 2013 w13856) found that C-A-B decreased time to completion of first CPR cycle by 15 s (P < 0.001). The clinical significance of this difference is unknown.

Treatment Recommendations

We suggest commencing CPR with compressions rather than ventilations (weak recommendation, very-low-certainty evidence).

Justification and Evidence to Decision Framework Highlights

For all outcomes starting with compressions resulted in faster times to key elements of resuscitation (rescue breaths, chest compressions, completion of first CPR cycle) across the four papers reviewed, with the exception of simulated paediatric resuscitation where starting with compressions delayed time to commencement of rescue breaths in cardiac arrest by 5.74 seconds: this difference was statistically significant but of questionable clinical significance (Lubrano 2012 p1473). This delay in commencing rescue breaths may be acceptable given the decreased time to other elements of resuscitation, however it should be noted that the certainty of the evidence is very low and all studies reviewed were manikin studies. There should also be consideration given to training requirements of a single approach versus separate approaches for adults and children.

Knowledge Gaps

No human studies evaluating this question in any setting were identified. Important uncertainties regarding timing and delays in initiation of the CPR components (chest compressions, opening airway, and rescue breaths) remain, and may not be readily extrapolated from manikin studies.


Evidence-to-Decision Table: Starting CPR


Kobayashi, M., Fujiwara, A., Morita, H., Nishimoto, Y., Mishima, T., Nitta, M., Hayashi, T., Hotta, T., Hayashi, Y., Hachisuka, E., 2008. A manikin-based observational study on cardiopulmonary resuscitation skills at the Osaka Senri medical rally. Resuscitation 78 (3), 333.

Lubrano, R., Cecchetti, C., Bellelli, E., Gentile, I., Levano, H.L., Orsini, F., Bertazzoni, G., Messi, G., Rugolotto, S., Pirozzi, N., 2012. Comparison of times of intervention during pediatric CPR maneuvers using ABC and CAB sequences: a randomized trial. Resuscitation 83 (12), 1473.

Marsch, S., Tschan, F., Semmer, N., Zobrist, R., Hunziker, P.R., Hunziker, S., 2013. ABC versus CAB for cardiopulmonary resuscitation: a prospective, randomized simulator-based trial. Swiss medical weekly 143, w13856.

Sekiguchi, H., Kondo, Y., Kukita, I., 2013. Verification of changes in the time taken to initiate chest compressions according to modified basic life support guidelines. The American journal of emergency medicine 31 (8), 1248.



Виктория Антонова
(397 posts)
It is very strange to change a previous COSTR recommendation without any new evidence nor consulting the paediatric taskforce in this? This makes one thoroughly question the validity of the Grade process. When looking at the EtD table a clear difference between adult and child is made but for some reason this is not very well reflected in the TR and justification. In my opninion the clinical evidence provided (all older than 2015) is not sufficient to warrent such a recommendation, knowing
Виктория Антонова
(397 posts)
Why is there a change in recommendations in the absence of any new evidence?? There is a substantial difference in adult and paediatric resuscitation but this was not reflected in the justification and treatment recommendations at all. The clinical evidence in not new norr sufficient for the change of recommendation in my opinion. The value of chest compressions in CA secondary to asphyxia where blood is already almost completely deprived of oxygen is debatable at the best (most cases of paediatric CAs). Also, for the same pathophysiological reason, the ERC started to recommend in 2015 the initial 5 rescue breaths not only for paediatric resuscitation but also for drowning (in the special circumstances section).
Виктория Антонова
(397 posts)
Thank you for your comments. These are adult guidelines, but could probably have been marked more clearly. The BLS ILCOR treatment recommendation in 2015 was: "We suggest commencing CPR with compressions rather than ventilations (weak recommendation, very-low-quality evidence)."
Виктория Антонова
(397 posts)
I would welcome a change in recommendation. My experience from many simulation-based trainings and emergency care of pediatric patients shows that the chest compressions are carried out much later when using ABC compared to CAB, since a ready-to-use bag for bag-mask ventilation is rarely directly available. In my opinion, changing the recommendations would not delay bag ventilation, but decrease the time to initiation of chest compressions.
Виктория Антонова
(397 posts)
I totally agree with Ellen Heimbergs comment. I know very well both sides (AHA and ERC)For the pediatric patients it is important that someone does something as fast as possible, ...and -beside of any not really existing evidence for both pathways- it is at the end simply more realistic and pragmatic to start with CC. ...until REAL evidence tell us what is the best!
Виктория Антонова
(397 posts)
I very much support a change to CAB. The easier the algorithm the better the adherence to it. My experience on the PICU is that with a sudden or unwitnessed onset of cardiac arrest, staff mostly starts with chest compressions while calling for help, although staff is very well trained in ABC. Thus, ABC is not practical for most cardiac carrest cases in a PICU setting. Furthermore, do we really want two different algorithm approaches for BLS on one ward? Let’s make algorithms as simple and intuitive as possible and let’s adjust algorithms for pediatric and adolescent patients. This discussion is not just about a potential delay of ventilation – this is about how we can implement and adhere to algorithms best.

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