EIT 6311 - International facets of the ‘Chain of Survival’: EIT 6311; TF ScR

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.

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: Sebastian Schnaubelt, Robert Greif, and Koen Monsieurs are authors of included studies.

Task Force Synthesis Citation

Schnaubelt S, Fijacko N, Al-Hilali Z, Atiq H, Bigham B, Eastwood K, Odakha J, Olaussen A, Ko YC, Matsuyama T, Veigl C, Monsieurs KG, Greif R.- on behalf of the International Liaison Committee on Resuscitation Education, Implementation and Teams Task Force. International facets of the ‘Chain of Survival’. Scoping review and Task Force Insights [Internet] Brussels, Belgium: International Liaison Committee on Resuscitation (ILCOR) Education, Implementation and Teams Task Force, 2023 December1. Available from: http://ilcor.org

Methodological Preamble and Link to Published Scoping Review

This scoping review was conducted by nine experts of the ILCOR EIT Task Force Scoping Review team and four external content experts. Evidence for adult and paediatric literature was sought and considered by the EIT Task Force. The EIT task force discussed the evidence and provided insights.

Webmaster to insert the Scoping Review citation and link to Pubmed when/if it is available.

We expect to submit this Scoping Review for publication in January 2024.

PICOST

The PICOST (Population, Intervention, Comparator, Outcome, Study Design and Timeframe) was defined as follows:

Population: Literature using the term “chain of survival” or similar terms (e.g., “survival chain”, “chain of [other pathology]”)

Intervention and exposure: Adaptations of the original “chain of survival” …

Comparators: …compared to the original “chain of survival”

Outcomes:

• Composition of the specific variations in adapted versions
• Attitudes, rationale, and views concerning the adaptation
• Incentives to develop novel versions
• Way of implementation of adapted versions
• Way of utilization of adapted versions in education
• Variations in visualization
• Effect of the use of the chain of survival or variants on teaching, implementation, patient outcomes

Study Designs:

• All types of studies - randomized or non-randomized (controlled) trials), non-original / narrative literature like letters, commentaries, or editorials.
• All languages.

Timeframe: All years. Literature search updated to 14 August, 2023.

Search Strategies and Screening

The search strategy was performed by information specialist Mary-Doug Wright (ILCOR, USA), finalized on 15 August 2023, and peer-reviewed by a second IS (Medical University of Vienna, Austria) on 12 September 2023.

Databases searched were MEDLINE(R) ALL 1946 to 1974 to August 14, 2023 (Ovid); Embase 1974 to 2023 August 14 (Ovid); APA PsycINFO 1806 to August Week 1 2023 (Ovid); CINAHL 1982-present (Ebscohost); ERIC 1966-present (Ebscohost); Web of Science (Clarivate); Scopus (Elsevier); Cochrane Library (Wiley Online) – Cochrane Central Register of Controlled Trials Issue 7 of 12, July 2023 and Cochrane Database of Systematic Reviews Issue 8 of 12, August 2023. See Annex I for the full search strategies.

1704 abstracts were imported in Rayyan (rayyan.qcri.org) and screened independently by Sebastian Schnaubelt, Zehra Al-Hilali, Huba Atiq, Blair Bigham, Kathryn Eastwood, Justine Odakha, Alexander Olaussen, Ying-Chih Ko, Tasuku Matsuyama, Christoph Veigl, Koen Monsieurs, and Robert Greif. Nine additional abstracts which were found as cross citations in the reviewing process were added by the reviewers, leading to a total of 1713 screened abstracts. Conflicting decisions were resolved by agreement. Ten duplicates were deleted, and 469 articles were decided upon for full-text retrieval, as often, the abstracts were not sufficient informative to make a decision. After having assessed the full-texts, 426 publications were excluded, leaving 43 articles to be included in the review.

Important note: The Task Force originally also wanted to specifically screen grey literature and social media for content about the chain of survival, as critical content could have been just produced and made public for educational or awareness purposes and not published in peer-reviewed journals. In correspondence with the information specialist, this was subsequently cancelled due to resource limitations and no clear definitions in the ILCOR evidence synthesis process of how to address grey literature in a structured way; however, this approach should be re-addressed in future review updates.

Inclusion and Exclusion criteria

Generally, only publications communicating something novel (and not just repeating) on the chain of survival were included. If a novel version of the chain of survival was described by several authors, we included all because we did not want to judge who had the idea first.

Note: An inclusion into this Scoping Review does not necessarily mean the respective author was the first to describe a specific adaptation of the chain of survival.

Inclusion Criteria:

• Publications describing novel adaptations/ modifications of the chain of survival.
• Publications describing various kinds of the chain of survival (e.g., for OHCA and for IHCA).
• Publications describing an implementation process or use of the chain of survival in an educational setting or awareness campaign.

Exclusion criteria:

• Publications only mentioning the chain of survival, or describing the term in the original sense
• Publications only emphasizing that individual links of the chain of survival must be “strengthened”.
• Older publications suggesting additions to the chain of survival that were later adopted in the official version (in most cases this was a 5^th link).
• Publications using the term chain of survival as a synonym for their “system to save lives” program (e.g., description how the “chain of survival” was worked on when a new public access defibrillator program was implemented).

Data Table: EIT 6311 Data Tables

Task Force Insights

1. Why this topic was reviewed

This topic was chosen for review by the EIT Task Force because of an ongoing and growing heterogeneity in the “chain of survival”, leading to confusion within the community (which version should be used for which purpose? Are there differences in educational or clinical outcomes?).

The term is internationally widely used in literature, scientific and popular presentations, and education, as well as in awareness campaigns. In the latest respective guidelines of two of the major resuscitation councils influencing resuscitation practice, the American Heart Association (AHA) and the European Resuscitation Council (ERC), only the AHA uses various iterations of the chain of survival. [1] The ERC switched to “systems saving lives”, and, while still mentioning the chain of survival, does not actively use a depiction of the chain of survival any more [45]. There is no clear opinion on what kind of chain is to be used in which situation, if it should be adapted, or if the topic is of importance at all. No previous systematic approach or statement on this was issued by ILCOR.

The chain of survival was first systematically addressed in an American Heart Association (AHA) statement by Cummins et al. in 1991 [2], and dates back to similar concepts by Friedrich Wilhelm Ahnefeld [3] or the first steps of modern CPR by Peter Safar [46]. Back in the nineties, it was stated that “more people can survive sudden cardiac arrest when a particular sequence of events occurs as rapidly as possible”. [2] That train of thought is still applicable today: the sequence of “Early access”, “Early CPR”, “Early defibrillation”, and “Early advanced care” [2] are cornerstones of all current guidelines [1]. The AHA defines the “chain of survival” as […] the critical actions that must occur in rapid succession to maximize the chance of survival from cardiac arrest”, and refers to it in its most recent CPR guidelines. [47] The European Resuscitation Council (ERC) also uses the term in its latest guidelines, and describes the “chain of survival” as “The actions linking the victim of sudden cardiac arrest with survival […]”, and closely links it to the “formula of survival”. [48,49]

However, a range of the term can be noted, and various different kinds of the chain of survival have been developed, published, and recommended for use by developers. Moreover, the term is not limited to CPR anymore, but is also used in different contexts like stroke or drowning. Also, there are novel technical developments that progressively tend to be integrated into existing systems. [1,30,50,51] Such adaptations are necessary but apparently lead to a variety of different chains of survival; all without a sound underlying system. Moreover, low- and middle-income countries and low-resource settings in general may require entirely different resource and priority allocations than high-resource environments. A chain of survival developed by people from high-income areas can thus have severe limitations in true global implementation: One can hardly expect clinicians fighting for most basic patient needs to also think about drones or extracorporeal life support. The “generic” or “universal” chain of survival would therefore have to be tailored to achieve international recognition beyond the view from high-resource settings. Sub-versions would then again emerge due to the heterogeneity of the bespoke setting, ranging from local to system-wide levels.

Therefore, the EIT task force decided to provide a first overview of the various kinds of the chain of survival that have been described and used in the literature so far, as a base for discussions and maybe also towards a more structured use of the concept in the future.

2. Narrative summary of evidence identified

The 43 included publications originated from diverse geographical areas (Table 1), and there were large differences in the number of studies per region, with most originating in Europe (n=19), followed by North America (n=12). The majority (n=38, 9%) came from high-income countries, and none from low-income countries (as per definition of the World Bank, see Table 1).

Since the first description of the chain of survival in 1991, there has been an increase in publications over the years, with an upwards trend (Figure 1).

Figure 1: Publications on the chain of survival per year since its first description in 1991, with an upwards trend (dotted line).

Chain of survival fig 1

We classified the publication types into subgroups that were most suitable and internationally recognized (even though a specific journal may have classified a publication differently, e.g., “special report”), and thus report on four abstracts [26,32,40,42], two commentaries [9,14], five editorials [10,12,13,27,29], ten letters [6–8,19,23,31,34–36,38], five concepts [11,20,24,30,37], three reviews [22,28,33], four statements [2,25,39,41], six reports of original research [5,15,16,21,43,44], and four guidelines [1,4,17,18].

As anticipated, despite the relatively large number of publications, heterogeneity and publication types made a systematic review or meta-analysis impossible.

We further grouped the publications (Table 2) into “novel kinds of the concept related to resuscitation” (n=8) [1] [2] [4] [5] [6] [7] [8] [9]T, “novel kinds of the concept not directly related to resuscitation” (n=23) [10] [11] [12] [13] [14] [15] [16] [17] [18] [19] [20] [21] [22] [23] [24] [25] [26] [27] [28] [29] [30] [31] [32], and “mere adaptations” (n=9) [33] [34] [35] [36] [37] [38] [39] [40] [41], and “impact on outcomes” (n=3) [42] [43] [44].

In brief, especially for resuscitation, novel chains of survival were suggested in terms of additional versions for IHCA [1] [4] [8] and paediatric resuscitation [1] [6], a chain of survival for mass gatherings (including early planning) [5], a chainmail of survival (expanding the linear concept of the chain into an interconnecting lattice concept with many links which are adaptive to various settings and situations) [7], and a chain of survival specific for China (three phases, also including cultural specifics) [9].

Mere adaptations of the existing chain as opposed to novel developments (mostly expansions of the chain) included extensions specific for survival after ventricular fibrillation (focusing on secondary prevention) [33], for rehabilitation [38], general prevention [39], or family support [40]. Also, there were suggestions of making the chain into a circle [34], a more detailed description of the chain for ST-elevation myocardial infarction [37], a variation of the chainmail of survival to low-resource settings [41], a depiction of survival odds along the chain in contrast to research funding [35], and a visual adaptation of the rings according to their relevance in ratios [36].

An impact of the chain of survival on patient outcomes was reported either as an observation of increased survival rates and better neurologic outcome after the introduction of the 5^th link of the chain by the AHA in 2010 [43] [44], and increased bystander CPR rates after a public campaign about the chain of survival in France [42]. No educational or other outcomes were reported.

Following the nature of a scoping review, also other versions or adaptations of the chain of survival which are not directly related to CPR were found [10] [11] [12] [13] [14] [15] [16] [17] [18] [19] [20] [21] [22] [23] [24] [25] [26] [27] [28] [29] [30] [31] [32], for example for specific pathologies like trauma [10] [29] [26] and severe hemorrhage [22], land mine incidents [16], stroke [18] [28], ST-elevation myocardial infarction [27] [12], drowning [32] [30], septic shock [19], complicated deliveries [15]), or occasions and situations (pandemics [13] [31], events [24], terror attacks [25], chemical/ biological/ radiological/ nuclear incidents [14], industrial incidents [20]). Variations which re-thought the concept include the “survival ladder” (each step leads closer to success) [23], or a “chain of survival behaviours” in first aid (defining domains of first aid education) [17]. As peculiarities, there was even an animal chain of survival for veterinary patients [11], and one for anaesthesia equipment [21], whereas the latter touches the important point of scarce resource settings.

3. Narrative Reporting of the task force discussions

There is a vast heterogeneity of the reported publications on the chain of survival, ranging from “classic” versions, for instance used by resuscitation councils, to small adaptations, and, finally, to completely novel versions. New types of the chain of survival don’t just cover cardiac arrest anymore but have also expanded into other pathologies or situations.

A dilemma arises: on the one hand, most healthcare workers involved in acute care will know one or another version of the chain of survival because the concept has penetrated respective scientific literature, guiding documents, and other types of publications including grey literature. Also, the term is often – clinically and scientifically – used as a synonym for whole systems of cardiac arrest care (ERC: “systems to save lives”).

The aspect of the educational concept or framework of the chain of survival does not really seem to play a role, at least not in the reported publications. On the other hand, the growing number of publications and opinions on the topic as well as the many adaptations of the “classic” chain suggest that the original form and even updated forms (e.g., including post-arrest care) might lack various essential links. Whereas rehabilitation and prevention are being more and more accepted as cornerstones of patient care, other aspects like resource adaptation are still very new claims. Of course, specific situations, including special circumstances of cardiac arrest, paediatric cardiac arrest, out-of-hospital or in-hospital cardiac arrest, drowning, etc. may require more substantial modifications like the ones presented by the publications included in this review.

It is interesting that only three publications assessed the impact of the chain of survival on outcomes [42] [43] [44], and even those are probably heavily biased (with the assessed effects arising not only from the chain of survival concept as a theoretical framework but rather from a change in clinical practice; but in turn – inducing practical change may be one of the key assets of the chain of survival format).

The “classic” chain of survival (Figure 2) still seems a sensible choice as a “cognitive aid” to convey the message of needed actions to save lives for education, awareness campaigns, etc. for laypersons. Moreover, if needed, very specific versions of the chain for very specific situations like drowning or trauma might be also acceptable. In comparison, the chainmail of survival [7] [41] is open to include novel ideas (e.g., drones) and is adaptable to various resource settings, while staying in one format. It might be more valuable for professionals than for laypersons. The educational and implementational worth of a combined system (e.g., classic chain, chainmail, specific chains; Figure 3), as well as its parts and the impact on patient survival should be researched in the future.

In summary, there is a vast heterogeneity of chain of survival concepts deviating from the ones published in current guidelines. It is unclear how many versions are necessary, when and for whom the chain of survival should be used, and what worth it has concerning educational and clinical outcomes.

The Task Force thus concluded that:

• As a depiction and summative term for a “systems to save lives” program, the chain of survival with six links (as the only currently proposed by the AHA[1]) should be continued to be used in layperson education (= basic chain of survival) as an easy cognitive aid and depiction of a complex system. The proposed links are: 1) Recognition & Prevention 2) Early call for help 3) High quality CPR 4) Early defibrillation 5) Post-Cardiac Arrest care 6) Recovery & Rehabilitation (Figure 2).
• Specific versions of the chain of survival could be used for special circumstances of cardiac arrest (e.g. drowning, hypothermia, etc.). However, a wide variety of chains should be avoided.
• ILCOR as the international body on resuscitation should provide the basic structure of this framework, and regional resuscitation councils can provide regional application of the chain of survival for their implementation strategies.
• Future research on the concept is warranted, as mentioned under the Knowledge Gaps.

Figure 2: The basic chain of survival with six links. CPR = cardiopulmonary resuscitation; CA = cardiac arrest.

Chain of survival fig 2

Figure 3: The interaction of basic chain of survival, chainmail of survival, and potential specific versions for specific situations.

Chain of survival fig 3

Our review has limitations: We did not have the opportunity to search grey literature and social media, as originally intended. A great body of respective information could thus have been missed. Moreover, even though the Task Force aimed at increased inclusiveness when conducting this review by inviting content experts from non-high resource settings, we recognize that the majority of collaborators works in high-resource settings, therefore potentially conveying biased views.

Knowledge Gaps

The EIT Task Force identified the following knowledge gaps:

• It is unknown whether there is a need for revising the “classic” chain of survival.
• It is unclear who the chain of survival is targeted at (clinicians, scientists, laypeople, stakeholders, or all of them), if laypersons need a simpler chain of survival than health care providers, and what is its intended purpose (a depiction of local systems to save lives, an educational framework, a cognitive aid, etc.).
• It is unknown which of the various published chains of survival should be used by default; a comprehensive system could be evaluated for applicability in the future.
• There is insufficient data on the impact of various versions of the chain of survival on educational and clinical outcomes.

References

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Annex I – Search strategies

Ovid MEDLINE(R) ALL 1946 to August 14, 2023

Embase 1974 to 2023 August 14 (Ovid)

APA PsycInfo 1806 to August Week 1 2023 (Ovid)

CINAHL 1982-present (Ebscohost)

ERIC 1966-present (Ebscohost)

Web of Science Core Collection 1900-present (Clarivate)

Science Citation Index Expanded (1900-present)

Social Sciences Citation Index (1900-present)

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