CAB or ABC in drowning: Basic Life Support 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

Dunne C, Morgan P, Bierens J, Olasveengen T, Morley PT, Perkins GD. on behalf of the International Liaison Committee on Resuscitation BLS Life Support Task Force(s).

Ventilation of compression first strategies for drowning Consensus on Science with Treatment Recommendations [Internet] Brussels, Belgium: International Liaison Committee on Resuscitation (ILCOR) Advanced Life Support Task Force, 2021 Dec 6. Available from:

Methodological Preamble

There is ongoing debate in the scientific literature regarding the merits of commencing resuscitation with chest compressions prior to ventilations. Existing ILCOR recommendations for adult BLS “suggests commencing CPR with compressions rather than ventilations (weak recommendation, very-low-certainty evidence)” whilst the paediatric task force concluded that there was insufficient evidence to make a recommendation. The evidence base informing this recommendation is limited to data from four manikin studies with no human studies previously identified. Unlike the majority of adult cardiac arrests and some paediatric cardiac arrests which arise primarily due to a cardiac cause, drowning leading to cardiac arrest is primarily caused by hypoxia. Whether a different approach in the special circumstances associated with drowning warrants an alternative approach is uncertain.

This review was initiated following a request from the American Heart Association. The review was led by a group of drowning experts commissioned to undertake a series of reviews relating to drowning.

The continuous evidence evaluation process for the production of Consensus on Science with Treatment Recommendations (CoSTR) started with a systematic review the literature (Perkins et al 2021 PROSPERO CRD42021259983) conducted by Patrick Morgan, Cody Dunne, Samantha Johnson, Joost Bierens and Gavin Perkins with involvement of clinical content experts.

Evidence for adult and paediatric literature was sought and considered by the Basic Life Support Adult Task Force and the Paediatric Task Force groups respectively. These data were taken into account when formulating the Treatment Recommendations.



Adults and children in cardiac arrest1 following drowning2


Resuscitation which follows a compression first strategy (CAB)


Resuscitation which starts with ventilation first (ABC)


Critical 9: Survival to discharge / 30 days or later

Critical 8: Survival with favourable neurological outcome to discharge / 30 days or later

Critical 7: Return of spontaneous circulation (ROSC)

Study Design

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), manikin studies, narrative reviews and animal studies were excluded.

All years and all languages are included as long as there is an English abstract


Database inception to current time.

1A broad definition of cardiac arrest will be used including those who are unconscious and not breathing normally or those requiring resuscitation interventions e.g. chest compressions, defibrillation.

2 Drowning is the process of experiencing respiratory impairment from submersion/immersion in liquid

PROSPERO Registration CRD42021259983

Consensus on Science

A search of Medline, Pre-Medline, Embase, Cochrane Database of Systematic Reviews and Cochrane Central Register of Controlled Trials identified 1085 references. After de-duplication of references 730 references were reviewed. After review of titles and abstracts 9 papers were shortlisted for full text review. No studies were identified which addressed the PICOST question.

Treatment Recommendations

  • We recommend a compression-first strategy (CAB) for lay persons providing resuscitation for adults and children in cardiac arrest due to drowning (Good practice statement)

This prioritizes simplicity and cohesiveness in training recommendations for lay persons, with the goal of faster resuscitation initiation. This is supported by manikin studies finding limited delay in ventilations even with a compression-first strategy.

  • We recommend that health care professionals and those with a duty to respond to drowning (e.g. lifeguards) consider providing rescue breaths / ventilations first (ABC) prior to chest compressions if they have been trained to do so. (Good practice statement)

This considers that indirect evidence suggests earlier ventilations may improve prognosis, and the specialized training of lifeguards and healthcare professionals (including cardiac monitoring and ventilation-delivery equipment). The current evidence is unclear if earlier ventilations improve outcomes once cardiac arrest has occurred, or if the benefit is in preventing respiratory arrest deteriorating into cardiac arrest.

Justification and Evidence to Decision Framework


Seven hundred and thirty abstracts were reviewed, of which 9 proceeded for a full text read. Ultimately, no studies were identified as relevant to the PICO question comparing initial resuscitation strategies (ventilation-first or compression-first) for cardiac arrests due to drowning. In order to determine good practice statements, the reviewers identified literature and other consensus statements which indirectly related to the research question.

Rationale for the ventilation-first strategy (differing from adult BLS treatment recommendations) is due to the hypoxic mechanism of cardiac arrest in drowning, and belief that earlier ventilations will reverse the hypoxia sooner, and either prevent the patient from progressing from respiratory arrest to cardiac arrest or increase the likelihood of Return of Spontaneous Circulation (ROSC) after correcting the underlying aetiology.

This similar rationale is commonly held in paediatric cardiac arrest, where hypoxia is a more common than aetiology than primary cardiac events.[Lee 2019 7032] ILCOR reviewed the evidence for initial resuscitation strategy in paediatric cardiac arrest in both 2015 and 2020.[De Caen 2015 S177; Maconochie 2020 S140] No human studies were identified, and the task force did not recommend either strategy as superior. Instead, noting that a compression-first strategy prioritized uniformity with adult guidelines and simplicity, and a ventilation-first strategy prioritized hypoxia reversal sooner. Two manikin RCT studies were identified in the review that demonstrated ventilations were only delayed by 5.7-6.0s with a compression-first strategy compared to ventilation-first.[Marsch 2013 w13856; Sekiguchi 2013 1248]

There is only indirect evidence to support a ventilation-first strategy. Another systematic review is presently determining the impact of any ventilations at all as part of the resuscitation strategy, however a recent scoping review identified bystander CPR including ventilations as favourable for survival.[Bierens 2021 205]

In addition, one retrospective observational study compared in-water resuscitation (i.e., ventilations) versus none for drowning victims in respiratory (and possibly cardiac) arrest. Survival (87.5% versus 25.0%) and survival with favourable neurological outcome (52.6% versus 7.4%) was higher in the in-water resuscitation cohort.[Szpilman 2004 25] Another study describes significantly worse neurological outcomes in paediatric drowning patients who experience cardiac arrest compared to respiratory arrest only (81% versus 0%, p<0.001). By intervening with ventilations early in the arrest process before the heart has stopped (i.e., addressing the hypoxic mechanism), one may prevent worse outcomes.[Mtaweh 2015 91]

Of note, no direct or indirect evidence is available to support any certain number of initial ventilations if lifeguards or healthcare professionals adopt a ventilation-first strategy. Most importantly, resuscitation should not be delayed by either selected strategy.

Knowledge Gaps

There were no studies which directly evaluated this question. Further research, informed by the Utstein template for drowning may usefully address this on-going uncertainty.

Attachment: There is no ETD table as no evidence was identified.


References listed alphabetically by first author last name in this citation format (Circulation)

  1. Lee J, Yang WC, Lee E, Huang J, Hsiao H, Lin M, et al. Clinical survey and predictors of pediatric out-of-hospital cardiac arrest admitted to the Emergency Department. Nature. 2019;
  2. De Caen AR, Maconochie IK, Aickin R, Atkins DL, Biarent D, Guerguerian AM. Part 6: Pediatric Basic Life Support and Pediatric Advanced Life Support. Circulation. 2015; 132(16):S177-S203.
  3. Maconochie IK, Aickin R, Hazinski MF, Atkins DL, Bingham R, Couto TB, et al. Pediatric Life Support: 2020 International Consensus on Cardiopulmonary Resuscitation and Emergency Cardiovascular Care Science with Treatment Recommendations. Circulation. 2020;142:S140-S184.
  4. Marsch S, Tschan F, Semmer NK, Zobrist R, Hunziker PR, Hunziker S. ABC versus CAB for cardiopulmonary resuscitation: a prospective, randomized simulator-based trial. Swiss Med Wkly. 2013; 143:w13856.
  5. Sekiguchi H, Kondo Y, Kukita I. Verification of changes in the time taken to initiate chest compressions according to modified basic life support guidelines. Am J Emerg Med. 2013; 31:1248–1250.
  6. Bierens J, Abelairas-Gomez C, Barcala-Furelos R, Beerman S, Claesson A, Dunne C, et al. Resuscitation and emergency care in drowning: A scoping review. Resuscitation. 2021;162:205-217.
  7. Szpilman D, Soares M. In-water resuscitation – is it worthwhile? Resuscitation. 2004;63:25-31.
  8. Mtaweh H, Kochanek PM, Carcillo JA, Bell MJ, Fink EL. Patterns of multiorgan dysfunction after pediatric drowning. Resuscitation. 2015;90:91-96.



Leonard McFarlan
I would think extra energy or priority should be made to get the person out of the water ,other than stopping to give a breath .. Then a breath could be given .
Luvir Salac
If the cause of cardiac arrest in drowning is V fib then, CAB will be of great importance.
Kelly Martinez
Drowning protocol needs to focus on ventilations first. 5 or more initial breaths should be the standard before compressions.
Scott Ruddle
I agree that whether chest compressions come first or the resuscitation is started with ventilations likely makes little difference as shown by the manikin study. (The delay to set up ventilation equipment may change the time to first ventilation.) It would make instructing the procedure to lay rescuers easier if there was just one procedure advocated, CAB order of approach. However, education that drowning is a hypoxic event should be reinforced. Ventilations, preferably with supplemental oxygen, should be encouraged. Explain that compression only CPR may be less effective in this circumstance, since it does not address the hypoxia. Explain that ROSC can frequently occur without defibrillation since reversing the hypoxia corrects the lack of cardiac output.
David Symes
It would seem and feel right to continue the uniform approach of compression first for lay public or non specifically trained professionals. There is evidence that this group may be reluctant to undertake ventilation, especially if no barrier equipment is available,, thus prolonging the time before resuscitative efforts are commenced. The accepted ABC approach for those appropriately trained and equipped remains I believe the optimum response for this group.
Shinichiro Ohshimo
Congratulations on the completion of the Systematic Review! I appreciate your excellent work. I think this SR is a new recommendation on the order of resuscitation in drowning. One concern is that the cause of drowning may be a mixture of airway obstruction and non-respiratory causes such as fatal arrhythmia. Is it possible to make the same recommendation for drowning and cardiopulmonary arrest due to fatal arrhythmia?
Tony Bennison
Agreed. It is flawed to expect anyone to differentiate the underlying cause of the arrest in this scenario - it could be cardiac in origin, even in a fit, young individual.
Gerard Meijer
Is there a pre-ventilation action to clear the airway of any oropharyngeal 'foreign body' eg water, in the case of drowning by putting the casualty briefly on their side to allow whatever is there to 'drain' out? To ventilate extraneous water, bile or any liquid down into the bronchial system sound counterproductive.
Haldun Akoglu
(1 posts)
I think ventilation first approach is well known and accepted in public and repeatedly reinforced in movies and series. Moving towards CAB would actually mean a change from common knowledge for lay person education. For professionals, CAB should be thought as the only approach.
Carl Gwinnutt
As someone who lives by the coast and trains local lifeboat personnel they have recognised that those who suffer a cardiac arrest 'out at sea' can be divided into 2 main groups which I find quite interesting. The first is the 'youngsters' who are most likely to have drowned and have a hypoxic arrest. I have taught the crew that ventilation in this group with additional oxygen (they have facemark with the ability to add oxygen) is important and may in some cases be all that is required. Furthermore, trying to do quality CPR in a RIB is very difficult (see below). The second group are the older generation who frequently have co-morbidities and are more likely to have a primary cardiac cause of their arrest. In this group, the key thing is for them to start chest compressions as a primary procedure and get the person to the nearest AED. The crew have a map of all the AEDs along the coastline they cover and normally this only takes a few minutes, but is weather dependant. If this is delayed by more than a few minutes, they may then decide to add rescue breaths with supplementary oxygen. Doing CPR is very difficult but I decided to let them work out what they feel is the best position for the victim to make this as easy as possible, and they decided that they would lift the victim's legs up and place them on the side of the RIB! This of course may actually be beneficial and help with venous return. Food for thought..........
Leonardo Manino
I believe that ABC traditional (more than 50 years ) it's the best approach for drowning all ages patients/casualties . Whit the ABC sequence could reverse a pulmonary arrest with the first ventilations or prevents a Cardiopulmonary arrest depending on the stage the first responder / rescuer start the resuscitation . On the other hand the oxygen (supplementary or expired air ) will be necessary in that cases when the organs are deprived of oxygen due to the etiology of the cardiopulmonary arrest. In fact for all ages my opinion is that the ABC sequence its the best choice. in drowning patients .
Tony Bennison
I am very pleased that this issue is now the subject of a review - long overdue, in my opinion, and I believe the debate should be widened beyond the standard 'drowning = respiratory' model.. For a start, it is flawed to assume that the apnoeic patient pulled from water has 'drowned'.. The underlying cause could very well be cardiac in origin - even in an apparently healthy, young individual. The UK charity Cardiac Risk in the Young advise that the incidence of cardiac pathology is probably under-reported at post-mortem due to assumptions made that drowning is the primary cause, when there could have in fact been an underlying arrhythmia. Especially difficult to detect post-mortem if this was an electrical/metabolic disorder such as Brugadas, as opposed to a structural disorder such as HCM. This was graphically shown in the episode of 'Bondi Rescue' of the young Japanese student dragged from the sea in arrest. He was treated by the lifeguards in accordance with drowning protocols. On admittance to hospital it became apparent he had an underlying dysrhythmia. Second flawed assumption is that blowing expired air (or even via BVM) into the patients mouth results in improved oxygen saturations. This is too simplistic a justification for this approach, on which the science and evidence is - at best - inconclusive. Finally, the debate needs to get away from the respiratory vs cardiac argument and stop extrapolating what we assume from hospital or lab based studies. None of these include the mental and physical stress of extricating this patient in the first place, the practical challenge of trying to quickly and accurately identify normal vs agonal efforts and a pulse, all in difficult circumstances and usually a public place. Opening and maintaining a patent airway in these patients is sometimes impossible, as is trying to deliver effective ventilation without causing reflux.. Chest compressions are simple and straightforward in this situation - airway and breathing are often not - particularly for the non-health care professional. And above all we have to keep in mind that if we want to make these guidelines accessible to everyone, so that any bystander is willing to step forward, they have to be simple and reassuring - complexity is the enemy here and it is ridiculous to expect anyone to differentiate cardiac vs respiratory in this highly stressful, often panicky environment - the rescuer here will mostly be lay people who train infrequently and rarely experience the reality of pre hospital arrest - they need clear, unambiguous instructions. I believe the approach should be good quality chest compressions first and foremost, reassuring the rescuer that if the patient is in cardiac arrest, the compressions will help promote a perfusion pressure until the defib arrives, but if the patient has 'drowned' and is in respiratory arrest with an output, the compressions by themselves will often stimulate the patient to cough, gag, vomit/reflux - actions which in themselves may well restore normal breathing.. Yes of course - the longer the problem continues - oxygen will become more imperative - but it is only EMS with an airway adjunct/BVM/high flow 100% who can influence this - if the patient doesnt survive this event - whether cardiac or respiratory in origin, it could never be shown to be because a bystander had failed to do the 'Kiss of Life'.. Thank you for allowing me to comment and apologies for my long response, done on my phone! Best wishes to all.
Wess Long
In drowning scenarios, a CAB approach is problematic for lifeguards rescuing an unresponsive swimmer who has not suffered any other sort of a medical event. Emphasis should be placed to provide respirations as early as possible, including in the water if possible. Time is critically important when treating hypoxia from drowning. By not emphasizing immediate & effective breaths, there can be a considerable time lapse from the swimmer's last breath through the time to recognition, rescue, extrication, dry land assessment, and then begin compressions. This time can be further lengthened if an AED is introduced early and begins assessment. Without immediate breaths, this delay only further lengthens the time that the individual is in hypoxia which then decreases their chance of survival. Conversely 5 in-water or immediate respirations out of the water can be provided quickly and effectively prior to further care without significant delay. I firmly believe early and effective respirations interrupt the drowning process and ultimately save lives.
Richard Field
I agree that initial ventilations are likely to be of importance in drowning where the cause is hypoxia and this should be taught to those with a duty to respond (lifeguards/healthcare professionals/rescue personnel). However the big question is how many people are willing to do mouth to mouth ventilations? The last 2 years has especially made people more cautious about risks to responders in resuscitation situations. I feel it likely that most would delay ventilations until a barrier device or facemask is available and therefore time should be spent doing chest compressions first whilst awaiting for equipment. However, in certain situations a rescuer may need to wait for help to get the casualty out of the water in which it would be ideal if they could commence ventilations in this period. Another question would be regardless of which order ABC vs. CAB should the first set of ventilations be more than 2 i.e. 5 or more? The idea being to maximise oxygen delivery during the subsequent cycle of chest compressions; this will depend on if supplemental oxygen is being used, the tidal volume being delivered, the patients FRC and clearance of expired gases amongst other factors. The most important point is whatever oxygen you have managed to get into the patient you need it to get from the alveoli to the organs which is only achieved by minimising no-flow time! My suggestion would be if ventilations can be performed immediately give the 5 with an ABC approach. However if there is a delay in obtaining equipment/unwillingness to start without adjuncts then adopt a CAB approach and stick to the standard compression:ventilation ratio to keep it simple.
Chamila Jayasekera
(1 posts)
With a confirmed cardiac arrest and airways possibly flooded, it may be prudent to give chest compressions first with the hope of circulating whatever the oxygen. With the manikin study showing minimal delay in giving breaths and considering the fact that consistency is maintained across BLS , it may be best to recommend CAB in drowning.

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