# The association between the type of bystander and survival after an out-of-hospital cardiac arrest: A French nationwide study.

Hizia Benkerrou, Marguerite Lockhart, Matthieu Heidet, Ramy Azzouz, Christian Vilhelm, Hervé Hubert, Morgan Recher, Valentine Baert

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Hizia Benkerrou, Marguerite Lockhart, Matthieu Heidet, Ramy Azzouz, Christian Vilhelm, et al. The association between the type of bystander and survival after an out-of-hospital cardiac arrest: A French nationwide study. Resuscitation Plus, 2025, Resusc Plus, 21, pp.100858. 10.1016/j.resplu.2024.100858. hal-05076857

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Clinical paper

# The association between the type of bystander and survival after an out-of-hospital cardiac arrest: A French nationwide study

<figure><img src="image_4.png" /></figure>

Hizia Benkerrou<sup>a,b</sup>, Marguerite Lockhart<sup>a,c</sup>, Matthieu Heidet<sup>d,e</sup>, Ramy Azzouz<sup>a,b,f</sup>, Christian Vilhelm<sup>a,b</sup>, Hervé Hubert<sup>a,b</sup>, Morgan Recher<sup>a,c</sup>, Valentine Baert<sup>a,b,*</sup>, on behalf of the GR-RéAC<sup>b</sup>

## Abstract

**Background:** Early bystander interventions are associated with more favorable outcomes after out-of-hospital cardiac arrest (OHCA). The objective of the present study was to determine whether the type of bystander-patient relationship was associated with survival and neurological outcomes after OHCA in France.

**Methods:** We analyzed data registered in the French National Cardiac Arrest Registry (RéAC) between July 1st, 2011, and April 30th, 2023. The study population comprised bystander-attended cases of OHCA managed by the emergency medical services. Bystanders were categorized as family members, other laypersons, off-duty professional first responders, or off-duty healthcare professionals. The primary outcome was 30-day survival with a favorable neurological outcome (Cerebral Performance Category 1 or 2). The secondary outcomes included the bystander cardiopulmonary resuscitation (CPR) initiation rate, return of spontaneous circulation, and survival upon admission to the hospital. Our statistical analyses were based on bivariate and multivariable logistic regressions analyses.

**Results:** Among the 89,861 OHCA cases analyzed, family members constituted the largest group of bystanders (69.2%). Compared with non-family-member bystanders, family bystander status was associated with a lower CPR initiation rate, a longer no-flow time, and lower 30-day survival rates. Specifically, cases of OHCA with non-family-member bystanders were 32% more likely to survive with a CPC of 1–2 at day 30 than cases with family member bystanders. Medically trained bystander status (off-duty professional first responders and healthcare professionals) was associated with higher CPR initiation and 30-day survival rates, relative to nontrained laypersons.

**Conclusions:** Survival after an OHCA appears to be associated with the type of bystander. Although family members were the most common bystanders, they were less likely to initiate CPR and less likely to see the OHCA patient survive. Efforts to increase the post-OHCA survival rate should include targeted interventions (such as public education and training programs) that emphasize the importance of early CPR and automated external defibrillator use by family members.

**Keywords:** Out-of-hospital cardiac arrest, Cardiopulmonary resuscitation, Basic life support, Bystander interventions

## Introduction

Out-of-hospital cardiac arrest (OHCA) is a major health issue. The estimated annual incidence of OHCA in Europe is 84.0 per

100,000 person-years, with 30-day survival rates close to 8%.¹,² In France, the annual incidence is 61.5 per 100,000 person-years (corresponds to approximately 46,000 OHCAs annually) and the 30-day survival rate is only 5%.³ The management of OHCAs is generally based on the “chain of survival” concept, which comprises four steps:

**Abbreviations:** ALS, advanced life support, BLS, basic life support, CI, confidence interval, CPC, Cerebral Performance Category, CPR, cardiopulmonary resuscitation, EMS, emergency medical services, IQR, interquartile range, MICU, mobile intensive care unit, OHCA, out-of-hospital cardiac arrest, OR, odds ratio, RéAC, *Registre Électronique des Arrêts Cardiaques*, ROSC, return of spontaneous circulation

* Corresponding author at: ULR 2694 - METRICS: Évaluation des technologies de santé et des pratiques médicales, Institute of Health Engineering of Lille, University of Lille, 42, rue Ambroise Paré, F-59120 Loos, France.

E-mail address: valentine.baert@univ-lille.fr (V. Baert).

https://doi.org/10.1016/j.resplu.2024.100858

Received 16 October 2024; Received in revised form 18 December 2024; Accepted 23 December 2024
(i) early recognition, (ii) early cardiopulmonary resuscitation (CPR), (iii) early defibrillation, and (iv) advanced care.⁴ Bystander CPR is critically associated with favorable outcomes.⁵,⁶ Given that the no-flow time (i.e. the time interval between collapse and the initiation of CPR) and the time to defibrillation are two of the most important survival factors,⁷,⁸ bystander intervention is essential before the arrival of an emergency medical services (EMS) unit capable of providing basic life support (BLS) or advanced life support (ALS).⁹⁻¹³ However, bystander BLS initiation rates vary markedly from one country to another (e.g. from 13% in Serbia to 46% in France and over 82% in Norway).² Identifying the determinants of this variability might help to increase the frequency of bystander BLS provision. The relationship between the bystander and the patient may be one such determinant. According to the scientific literature, family bystanders rarely provide BLS or provide it with some delay, which reduced the chance of survival,¹⁴⁻¹⁹. However, this factor has not previously been evaluated in France.

Therefore, the primary objective of the present study was to determine whether the type of bystander-victim relationship was associated with survival and neurological outcomes after OHCA in France. The secondary objectives were to assess the association between the bystander-patient relationship and initiation of BLS and to describe time trends in layperson involvement in the response to OHCA.

# Method

## Study setting

In France, the Emergency Medical Services (EMSs) that manage OHCA are two-tiered. The first paramedic response and BLS are usually provided by the fire department. Advanced life support (ALS) is usually then provided by a physician-staffed mobile intensive care unit (MICU), coordinated by a medical dispatch center.²⁰ The MICU physician uses a specific, Utstein Style form to collect data on case characteristics, bystander interventions, intervention times, the initiation of BLS and/or ALS, and the patient's survival status immediately after the cardiac arrest. The data is sent to a secure database managed by the French National Cardiac Arrest Registry (Registre Électronique des Arrêts Cardiaques (RéAC); https://www.registreac.org).²¹,²² A follow-up report is filed 30 days after the OHCA or upon hospital discharge.

## Study data

We included patients from the RéAC database for the period of July 1st, 2011, and April 30th, 2023. Included variables regarding the context of the OHCA were, the year of OHCA, the location (at home or other public or private places) of OHCA, the presence of bystander at the time of collapse status (yes/no), the type of bystander (family member, off-duty professional first responder, off-duty healthcare professional, or other bystander). We also assessed the patient's baseline clinical characteristics, sex, age, medical history, bystander CPR status, first documented rhythm, no-flow and low-flow (time between first resuscitation gesture and ROSC or death) times, the initiation of ALS (including intubation and epinephrine injection), return of spontaneous circulation (ROSC), vital status upon admission to hospital, and 30-day follow-up data. All the definitions of collected data were based on the international Utstein Style template, Data collected according to previous

versions of the template have been transformed to follow the new definitions.²²

## Inclusion and exclusion criteria

We included all OHCA s with one or more bystanders but excluded cases in which the patient had clear signs of death (rigor mortis), patients with unknown cardiac rhythm, cases in which the patient had a normal cardiac rhythm at MICU's arrival, cases in which the rhythm was not recorded, and OHCA s lacking an obvious medical cause. A medical cause was defined (in line with the Utstein Style guidelines) as a cardiac cause, respiratory disease, neurological disease, anaphylaxis, asthma, and gastrointestinal bleeding. We also excluded cases with a no-flow time greater than 60 min upon the MICU's arrival and cases with missing data for BLS and 30-day survival.

## Main exposure

The main exposure was the bystander, defined as the first person who was not actively part of an organized emergency response system and who found or witnessed a patient having suffered from an OHCA.²¹ The bystander was classified into four categories: (i) a family member, (ii) an off-duty professional first responder, (iii) an off-duty healthcare professional, or (iv) another layperson (a passerby, a work colleague, etc.). Professional first responders and healthcare professionals were only considered if they were off-duty at the time of the OHCA.

## Outcomes

The primary outcome was 30-day post-OHCA survival with a good neurological outcome (defined as a Cerebral Performance Category (CPC) of 1 or 2).²³ The secondary outcomes were the bystander CPR initiation rate, ROSC, survival upon admission to hospital, and the overall hospital discharge and 30-day survival rates.

## Statistical analysis

Qualitative variables were described as the frequency (percentages). For quantitative variables, the normality of the data distribution was assessed using the Kolmogorov Smirnov test. Non-normally distributed variables were described as the median and interquartile range [IQR]). We compared bystander categories in three sets of analysis, as follows: (i) family members vs. all other bystanders (i.e. non-family-members), (ii) laypersons (family members and others) vs. medically trained persons (off-duty professional first responders and off-duty healthcare professionals), and (iii) family members vs. other laypersons vs. off-duty professional first responders vs. off-duty healthcare professionals.

We also compared the groups with regard to the OHCA context, intervention, and outcome. Univariate analyses were performed using Pearson's chi-squared test (for qualitative variables) and the Mann-Whitney U test or the Kruskal-Wallis test, as appropriate, for quantitative variables. Next, we performed bivariate and multivariate logistic regression analyses of the relationship between each study outcome and the bystander type. For the first two analyses described in the previous paragraph, the reference was "family member". For the third analysis, "layperson" was used as reference. For the multivariate analyses, we included 12 clinically or methodologically (identified with bivariate analysis) relevant potential confounders: the year of occurrence, sex (male/female/other), age (in years), personal medical history (six variables: heart disease/respiratory disease/diabetes/end-of-life scenario/other/none), no-flow time (in minutes),
location (home/public place/healthcare facility), treatment by a MICU (yes/no), and cardiac rhythm on the MICU's arrival (asystole/pulseless electrical activity/VF-pulseless VT/spontaneous activity). The odds ratio (OR) [95% confidence interval (CI)] was calculated for each variable.

Lastly, we reported time trends in the bystander CPR initiation rate and 30-day (D30) survival according to the bystander type (family member or other) and calculated the range (defined as the difference between the lowest and highest values recorded). We used the Cochran-Armitage test to assess the statistical significance of time trends in the BLS initiation rate.

The threshold for statistical significance in tests was set to p < 0.05. All statistical analyses were performed with R software (version 4.0.3).²⁴

## Ethics

In line with the French legislation on retrospective studies of anonymous medical registry data, the study protocol was approved by a hospital committee with competency for research not requiring authorization by an institutional review board. Likewise, patient consent was not required. The study database was registered with the French National Data Protection Commission (Commission nationale de l'informatique et des libertés (Paris, France); reference: 910946, dated April 6th, 2012), and the French Advisory Committee on Information Processing in Health Research (Comité Consultatif sur le Traitement de l'Information en matière de Recherche dans le domaine de la Santé (Paris, France); reference: 10.326Ter, dated October 14th, 2010).

## Results

From 2011 to 2023, 150,726 patients were included in the RéAC database. Of these, 60,865 met at least one exclusion criterion, and so 89,861 patients were included in the present analysis (Table 1): 62,210 (69.2%) in the family member group, 3,085 (3.4%) in the off-duty professional first responder group, 12,516 (13.9%) in the off-duty healthcare professional bystander group, and 12,050 (13.4%) in the other layperson group (Fig. 1).

Baseline characteristics of the population are described in the Table 1. The majority of OHCA patients were male (59,048 [65.7%]), and the median [IQR] age was 71 [59; 82]. In the majority of cases (62,421 [69.5%]), a bystander was present at the time of collapse. Bystanders initiated CPR in 47,042 (52.3%) cases, and an automated external defibrillator (AED) was applied in 7,467 (11.2%) cases. The median [IQR] no-flow time was 10 [4; 18] minutes, and the first rhythm recorded on the MICU's arrival was asystole in 72,081 (80.9%) cases. ALS was provided in 64,931 (72.3%) cases, and the median [IQR] low-flow time was 29 [16; 42] minutes. ROSC was observed in 19,005 (21.1%) cases, 15,860 (17.6%) cases were alive on arrival at hospital, and 4,348 (4.8%) were alive 30 days after OHCA or on discharge from hospital (Table 1).

### Patient characteristics, according to the type of bystander: Univariate analysis

#### Family member bystanders vs. all other bystanders

In this first comparison, we compared 62,210 family member bystanders with 27,651 non-family-member bystanders (Supplementary Table 1). For a family member bystander, the OHCA patient was more likely to be male (41,214 [66.2%] vs. 17,834 [64.5%] for a

non-family-member bystander, p < 0.001), the OHCA was more likely to occur at home (54,649 [94.2%] vs. 10,316 [40.0%], respectively, p < 0.001) and less likely to be witnessed (42,268 [67.9%] vs. 20,153 [72.9%], respectively, p < 0.001). Lastly, a family member bystander was less likely to perform CPR (27,320 [43.9%] vs. 19,722 [71.3%]) for a non-family-member bystander, p < 0.001), and OHCA patients with a family member bystander had longer no-flow times (11 [5; 18] minutes vs. 9 [1; 17] minutes for a non-family-member bystander, p < 0.001). In the group of patients with a family member as a witness, the use of an AED was less frequent than in the non-family member group (5.2% vs. 24.3%, p < 0.001) and these patients were less likely to achieve a good 30-day neurologic outcome (1,500 [2.4%] vs. 1,837 [6.7%], respectively, p < 0.001).

#### Laypersons vs. medically trained bystanders

We next compared 74,260 layperson bystanders with 15,601 medically trained bystanders (Supplementary Table 2). For a layperson bystander, the OHCA patient was more likely to be male (50,286 [67.7%] vs. 8,762 [56.2%] for a medically trained bystander, p < 0.001), and the OHCA was less likely to have been witnessed (50,023 [67.4%] vs. 12,398 [79.5%], respectively, p < 0.001). A layperson bystander was less likely to perform CPR (34,130 [46.0%] vs. 12,912 [82.8%] for a medically trained bystander, p < 0.001). OHCA patients with a layperson bystander had a lower 30-day CPC1/2 survival rate than patients with a (medically trained bystander (respectively 2,451 [3.3%] vs. 886 [5.7%], p < 0.001).

#### Family members vs. other laypersons vs. off-duty professional first responders vs. off-duty healthcare professionals

We next compared family member bystanders (n = 62,210) with other lay bystanders (n = 12,050), off-duty professional first responders (n = 3,085), and off-duty healthcare professionals (n = 12,516). (Supplementary Table 3). The OHCA was less likely to have been witnessed when the bystander was non-family layperson (7,755 [64.4%], vs. 42,268 [67.9%] for family members, 2,657 [86.1%] for off-duty professional first responders, and 9,741 [77.8%] for off-duty healthcare professionals, p < 0.001). Family member bystanders were the least willing to perform CPR (27,320 [43.9%], vs. 6,810 [56.5%] for other laypersons, 2,792 [90.5%] for off-duty professional first responders, and 10,120 [80.9%] for off-duty healthcare professionals, p < 0.001). The 30-day CPC1/2 survival rate was lowest for family member bystanders in this group (1,500 [2.4%], vs. 951 [8.0%] for other laypersons, 311 [10.2%] for off-duty professional first responders, and 575 [4.6%] for off-duty healthcare professionals, p < 0.001).

#### Bystander type and survival outcomes

##### Family member bystanders vs. all other bystanders

In the first regression model, we compared family member bystanders with all other bystanders (Table 2). In our adjusted analyses, the presence of a non-family-member bystander had higher odds ratio of CPR initiation (OR = 2.79 [2.68–2.91]), more likely ROSC (OR = 1.12 [1.06–1.18]), and higher odds ratio of survival at admission to hospital (OR = 1.19 [1.12–1.25]).

#### Laypersons vs. medically trained bystanders

In the second regression model, we compared layperson bystanders with medically trained bystanders (Table 3). Our adjusted analyses
<table><caption>Table 1 - Characteristics of the study population.</caption><thead><tr><th></th><th>Study population (n = 89,861)</th></tr></thead><tbody><tr><td>Cases per year</td><td></td></tr><tr><td>2011</td><td>493 (0.5)</td></tr><tr><td>2012</td><td>4462 (5.0)</td></tr><tr><td>2013</td><td>8778 (9.8)</td></tr><tr><td>2014</td><td>8677 (9.7)</td></tr><tr><td>2015</td><td>9264 (10.3)</td></tr><tr><td>2016</td><td>8779 (9.8)</td></tr><tr><td>2017</td><td>8848 (9.8)</td></tr><tr><td>2018</td><td>8781 (9.8)</td></tr><tr><td>2019</td><td>8423 (9.4)</td></tr><tr><td>2020</td><td>8141 (9.1)</td></tr><tr><td>2021</td><td>7387 (8.2)</td></tr><tr><td>2022</td><td>6431 (7.2)</td></tr><tr><td>2023</td><td>1397 (1.6)</td></tr><tr><td>Sex (male)</td><td>59,048 (65.7)</td></tr><tr><td>Age (years)</td><td>71 [59; 82]</td></tr><tr><td>Medical history</td><td></td></tr><tr><td>Heart disease</td><td>40,975 (45.6)</td></tr><tr><td>Respiratory disease</td><td>12,983 (14.4)</td></tr><tr><td>Diabetes</td><td>12,835 (14.3)</td></tr><tr><td>End-of-life scenario</td><td>3113 (3.5)</td></tr><tr><td>Other</td><td>30,100 (33.5)</td></tr><tr><td>None</td><td>7885 (8.8)</td></tr><tr><td>OHCA location (home)</td><td>64,965 (77.5)</td></tr><tr><td>Witnessed OHCA</td><td>62,421 (69.5)</td></tr><tr><td>No-flow time (min)</td><td>10 [4; 18]</td></tr><tr><td>Bystander CPR</td><td>47,042 (52.3)</td></tr><tr><td>Bystander type</td><td></td></tr><tr><td>Family</td><td>62,210 (69.2)</td></tr><tr><td>Other layperson</td><td>12,050 (13.4)</td></tr><tr><td>Off-duty professional first responder</td><td>3085 (3.4)</td></tr><tr><td>Off-duty healthcare professional</td><td>12,516 (13.9)</td></tr><tr><td>CPR provided by the bystander</td><td></td></tr><tr><td>Ventilation only</td><td>194 (0.4)</td></tr><tr><td>Chest compression + ventilation</td><td>10,954 (24.1)</td></tr><tr><td>Chest compression only</td><td>34,319 (75.5)</td></tr><tr><td>AED application by the bystander</td><td>7467 (11.2)</td></tr><tr><td>Bystander AED shock when applied</td><td>2405 (35.3)</td></tr><tr><td>First MICU-recorded cardiac rhythm</td><td></td></tr><tr><td>Asystole</td><td>72,081 (80.9)</td></tr><tr><td>PEA</td><td>6115 (6.9)</td></tr><tr><td>VF/pulseless VT</td><td>7708 (8.6)</td></tr><tr><td>ROSC</td><td>3221 (3.6)</td></tr><tr><td>MICU-treated</td><td>64,931 (72.3)</td></tr><tr><td>Tracheal intubation</td><td>59,794 (66.5)</td></tr><tr><td>Epinephrine administration</td><td>58,335 (65.0)</td></tr><tr><td>Low-flow time (min)</td><td>29 [16; 42]</td></tr><tr><td>ROSC</td><td>19,005 (21.1)</td></tr><tr><td>Alive on arrival at hospital</td><td>15,860 (17.6)</td></tr><tr><td>Alive at 30 days</td><td>4348 (4.8)</td></tr><tr><td>CPC 1–2 at 30 days</td><td>3337 (3.7)</td></tr></tbody></table>

Results are presented as frequency (percentage) or median [IQR].

* The year 2011 was from July to December and the year 2023 was from January to April.

AED: automated external defibrillator; BLS: basic life support; CPR: bystander cardiopulmonary resuscitation; CPC: Cerebral Performance Category; MICU: mobile intensive care unit; OHCA: out-of-hospital cardiac arrest; PEA: pulseless electrical activity; ROSC: return of spontaneous circulation; VF/pulseless VT: ventricular fibrillation/pulseless ventricular tachycardia.

showed that the presence of a medically trained bystander was associated with higher survival rates. The presence of a medically trained bystander was associated with higher odds ratio of CPR initiation and ROSC (OR = 7.38 [6.96–7.84]), ROSC (OR = 1.22 [1.15–1.29]) and higher odds ratio of survival upon admission to hospital (OR = 1.28 [1.20–1.36]). Patients with a medically trained bystander had better odds ratio of CPC1/2 at D30 than those who did not (OR = 1.69 [1.50–1.89]).
<figure><img src="image_5.png" /><figcaption>**Fig. 1 - Study flowchart.**</figcaption></figure>

*Family members vs. other laypersons vs. off-duty professional first responders vs. off-duty healthcare professionals*

In the third and last regression model, we compared four bystander groups: family members vs. other laypersons vs. off-duty professional first responders vs. off-duty healthcare professionals (Table 4). Our adjusted analyses showed that when compared with family members, the presence of off-duty professional first responders or off-duty healthcare professionals was associated with greater survival rates. Patients with an off-duty professional first responder or off-duty healthcare professional bystander had better odds ratio of CPC1/2 at D30 than those with other bystander types (OR = 1.76 [1.45–2.13] and 1.67 [1.44–1.94], respectively). The presence of an off-duty professional first responder bystander or an off-duty healthcare professional bystander was associated with higher odds ratio od CPR initiation (OR = 14.75 [12.87–16.96] and 6.38 [5.98–6.81], respectively) and higher rate of survival upon admission to hospital (OR = 1.45 [1.30–1.61] and 1.25 [1.15–1.35], respectively).

When compared with family members, the “other lay bystander” class was not associated with higher odds ratio of D30 CPC1/2 survival (OR = 1.02 [0.89–1.17]) but was associated with higher offs ratio of CPR initiation (OR = 1.10 [1.04–1.16]) and higher odds ratio of admission to hospital (OR = 1.08 [1.01–1.15]).

*Time trends in bystander involvement*

We analyzed time trends in CPR initiation and 30-day CPC1/2 survival rates with regard to family members and other layperson (Fig. 2.A and Fig. 2.B, respectively). The family member bystander group was associated with a significant increase over time in the CPR initiation rate; the range was 25.4 percentage points. However, the increase over time in the 30-day CPC1/2 survival rate was not significant (p = 0.620, range = 1.5 percentage points). In the other layperson group, we observed a significant increase over time in the CPR initiation rate; the range was 29.2 percentage points. How-
<table><caption>**Table 2 – Bivariate and multivariable logistic regression analyses of outcomes by type of bystander (family vs. non-family).**</caption><thead><tr><th>Outcome</th><th>Study group</th><th>Bivariate model<br>OR [95% CI]</th><th>Multivariate model*<br>OR [95% CI]</th></tr></thead><tbody><tr><td rowspan="2">CPC 1–2 at 30 days</td><td>Family</td><td>ref.</td><td>ref.</td></tr><tr><td>Non-family</td><td>2.90 [2.70; 3.11]</td><td>1.32 [1.18; 1.48]</td></tr><tr><td rowspan="2">Bystander CPR</td><td>Family</td><td>ref.</td><td>ref.</td></tr><tr><td>Non-family</td><td>3.18 [3.08; 3.28]</td><td>2.79 [2.68; 2.91]</td></tr><tr><td rowspan="2">ROSC</td><td>Family</td><td>ref.</td><td>ref.</td></tr><tr><td>Non-family</td><td>1.51 [1.46; 1.56]</td><td>1.12 [1.06; 1.18]</td></tr><tr><td rowspan="2">Alive on arrival at hospital</td><td>Family</td><td>ref.</td><td>ref.</td></tr><tr><td>Non-family</td><td>1.72 [1.66; 1.78]</td><td>1.19 [1.12; 1.25]</td></tr><tr><td rowspan="2">Alive at 30-day</td><td>Family</td><td>ref.</td><td>ref.</td></tr><tr><td>Non-family</td><td>2.76 [2.59; 2.93]</td><td>1.27 [1.15; 1.41]</td></tr></tbody></table>

<table><caption>**Table 3 – Bivariate and multivariable logistic regression analyses of outcomes by type of bystander (layperson vs. medically trained).**</caption><thead><tr><th>Outcome</th><th>Study group</th><th>Bivariate model<br>OR [95%CI]</th><th>Multivariate model*<br>OR [95%CI]</th></tr></thead><tbody><tr><td rowspan="2">CPC 1–2 at 30 days</td><td>Layperson</td><td>ref.</td><td>ref.</td></tr><tr><td>Medically trained</td><td>1.77 [1.63; 1.91]</td><td>1.69 [1.50; 1.89]</td></tr><tr><td rowspan="2">Bystander CPR</td><td>Layperson</td><td>ref.</td><td>ref.</td></tr><tr><td>Medically trained</td><td>5.65 [5.40; 5.90]</td><td>7.38 [6.96; 7.84]</td></tr><tr><td rowspan="2">ROSC</td><td>Layperson</td><td>ref.</td><td>ref.</td></tr><tr><td>Medically trained</td><td>1.22 [1.18; 1.28]</td><td>1.22 [1.15; 1.29]</td></tr><tr><td rowspan="2">Alive on arrival at hospital</td><td>Layperson</td><td>ref.</td><td>ref.</td></tr><tr><td>Medically trained</td><td>1.22 [1.17; 1.27]</td><td>1.28 [1.20; 1.36]</td></tr><tr><td rowspan="2">Alive at 30-day</td><td>Layperson</td><td>ref.</td><td>ref.</td></tr><tr><td>Medically trained</td><td>1.64 [1.53; 1.76]</td><td>1.54 [1.39; 1.72]</td></tr></tbody></table>

ever, increase over time in the 30-day CPC1/2 survival rate was not significant (p = 0.802, range = 9.2 percentage points).

Discussion

Based on data drawn from a nationwide, retrospective, observational cohort of OHCAs in France, our present findings indicate that patients who suffered from OHCA in presence of a non-family-member bystander were more likely to survive with a favorable neurological status at 30 days. Moreover, patients of OHCAs in the pres-

ence of professional first responder and healthcare professional bystanders were more likely to survive with a favorable neurological status at 30 days, relative to patients with a family-related bystander.

In line with several other studies, we found that family member bystanders are least likely to provide CPR.⁶,¹⁹,²⁵,²⁶ There are several possible explanations for this low rate. Psychological factors can significantly influence a person's response to a cardiac arrest: family members witnessing a cardiac arrest by their loved one may experience shock, fear, or disbelief.²⁷⁻³⁰ These emotional factors might cause the bystander to fail to recognize the severity of the situation and might prevent them from taking effective, immediate action. In

<footnote>* adjusted for year, sex, age, medical history, location, no-flow time, MICU-treated and first MICU-recorded cardiac rhythm.</footnote>

<footnote>CI: confidence interval; CPC: Cerebral Performance Category; CPR: cardiopulmonary resuscitation; OR: odds-ratio; ROSC: return of spontaneous circulation.</footnote>

<footnote>* adjusted for year, sex, age, medical history, location, no-flow time, MICU-treated and first MICU-recorded cardiac rhythm.</footnote>

<footnote>CI: confidence interval; CPC: Cerebral Performance Category; CPR: cardiopulmonary resuscitation; OR: odds-ratio; ROSC: return of spontaneous circulation.</footnote>
<table><caption>Table 4 – Bivariate and multivariable logistic regression analyses of the outcome by type of bystander (family vs. off-duty professional first responder vs. off-duty healthcare professional vs. other layperson).</caption><thead><tr><th>Outcome</th><th>Study group</th><th>Bivariate model<br>OR [95%CI]</th><th>Multivariate model*<br>OR [95%CI]</th></tr></thead><tbody><tr><td rowspan="4">CPC 1–2 at 30 days</td><td>Family</td><td>ref.</td><td>ref.</td></tr><tr><td>Off-duty professional first responder</td><td>4.57 [4.01; 5.19]</td><td>1.76 [1.45; 2.13]</td></tr><tr><td>Off-duty Health. Pro</td><td>1.95 [1.77; 2.15]</td><td>1.67 [1.44; 1.94]</td></tr><tr><td>Other layperson</td><td>3.50 [3.22; 3.80]</td><td>1.02 [0.89; 1.17]</td></tr><tr><td rowspan="4">Bystander CPR</td><td>Family</td><td>ref.</td><td>ref.</td></tr><tr><td>Off-duty professional first responder</td><td>12.17 [10.80; 13.77]</td><td>14.75 [12.87; 16.96]</td></tr><tr><td>Off-duty Health. Pro</td><td>5.36 [5.15; 5.66]</td><td>6.38 [5.98; 6.81]</td></tr><tr><td>Other layperson</td><td>1.66 [1.60; 1.73]</td><td>1.10 [1.04; 1.16]</td></tr><tr><td rowspan="4">ROSC</td><td>Family</td><td>ref.</td><td>ref.</td></tr><tr><td>Off-duty professional first responder</td><td>1.98 [1.83; 2.14]</td><td>1.30 [1.17; 1.44]</td></tr><tr><td>Off-duty Health. Pro</td><td>1.22 [1.16; 1.28]</td><td>1.19 [1.11; 1.28]</td></tr><tr><td>Other layperson</td><td>1.73 [1.65; 1.81]</td><td>1.02 [0.96; 1.09]</td></tr><tr><td rowspan="4">D0 Survival</td><td>Family</td><td>ref.</td><td>ref.</td></tr><tr><td>Off-duty professional first responder</td><td>2.32 [2.14; 2.51]</td><td>1.45 [1.30; 1.61]</td></tr><tr><td>Off-duty Health. Pro</td><td>1.23 [1.17; 1.29]</td><td>1.25 [1.15; 1.35]</td></tr><tr><td>Other layperson</td><td>2.14 [2.04; 2.24]</td><td>1.08 [1.01; 1.15]</td></tr><tr><td rowspan="4">D30 survival</td><td>Family</td><td>ref.</td><td>ref.</td></tr><tr><td>Off-duty professional first responder</td><td>4.03 [3.58; 4.54]</td><td>1.59 [1.33; 1.89]</td></tr><tr><td>Off-duty Health. Pro</td><td>1.84 [1.68; 2.00]</td><td>1.56 [1.36; 1.79]</td></tr><tr><td>Other layperson</td><td>3.44 [3.20; 3.70]</td><td>1.04 [0.92; 1.17]</td></tr></tbody></table>

contrast, non-family members are less likely to be burdened by these intense emotional factors and so are more likely to act swiftly.

We found that family member bystanders were the least likely to use an AED. Again, there are several possible explanations for this reluctance. The scientific literature shows that when the bystander is a family member, the OHCA is more likely to have occurred at home (i.e. a non-public place where an AED is less likely to be available).<sup>26,29–34</sup> All these factors contribute to lower survival rates with family member bystanders. Indeed, our adjusted analysis revealed a 32% greater chance of 30-day CPC1/2 survival when the bystander was not family-related. Several studies have found similar results,<sup>14,15,17,19</sup> however, the most frequent bystanders in our study were family members (69.2%). This observation is in line with the scientific literature again and show that family members should be trained to be effective OHCA witness.<sup>19,29,35</sup>

The time-trend analysis showed a significant increase in the frequency of CPR initiation by a family member bystander, with a rise between 2012 and 2023. At first sight, these results are quite encouraging. However, we did not observe a statistical significance change over time in the 30-day CPC1/2 survival, with a range of 1.5%. Those two observations raise questions about the time to BLS initiation and the quality of the BLS initiation, since the initiation of BLS is known to be the most important factor in OHCA survival.<sup>5,6,9,11</sup> Indeed, it is reasonable to assume that the time to BLS initiation and the quality of the BLS initiation are at least partly responsible for this discrepancy. One possible explanation for the increase over the last decade in the frequency of BLS initiation by family members could be that

dispatching centers have been widely encouraged and trained to provide telephone guidance on CPR to bystanders at the scene of the OHCA.<sup>36,37</sup> This telephone guidance might encourage the bystander to perform CPR but, as reported previously, has not yet had an impact on survival rates – probably due to the poor quality of CPR initiation.<sup>38</sup> Another possible explanation is the long time to BLS initiation. Indeed, it has been reported previously that the no-flow time is one of the most important survival factors for OHCAs.<sup>7,8</sup> In this line, a study found that the no-flow time during layperson CPR has increased significantly over time.<sup>39</sup> These results should be the subject of further investigation. Furthermore, prior training and experience in emergency response might be more common among non-family members and might contribute to the observed difference in survival outcomes. Individuals who have received BLS training or have already handled an emergency situation might feel more confident and competent in performing CPR and in calling for professional assistance. In contrast, family members who lack such training might be hesitant or unsure of the appropriate actions to be taken in the critical moments following a cardiac arrest.<sup>28,29</sup> Our results support the hypothesis whereby training helps to increase the chances of survival: the likelihood of 30-day CPC1/2 survival was 69% greater when the bystander was medically trained, compared with a layperson.<sup>18,40</sup>

Our findings indicate that public health strategies aimed at improving cardiac arrest survival rates must be modified profoundly. It is clear that providing BLS training to the general public (e.g. the “Kids Save Lives” project promoted by the European Resuscitation

<footnote>* adjusted for year, sex, age, medical history, location, no-flow time, MICU-treated and first MICU-recorded cardiac rhythm.</footnote>

<footnote>CI: confidence interval; CPC: Cerebral Performance Category; CPR: cardiopulmonary resuscitation; OR: odds-ratio; ROSC: return of spontaneous circulation.</footnote>
<figure><img src="image_6.png" /><figcaption>Fig. 2 - A: Trends in the rate of bystander CPR initiation by type of bystander/ B: Time trends in the 30-day CPC1/2 survival rate, by type of bystander.</figcaption></figure>

Council) is of paramount importance.⁴¹⁻⁴³ The “Kids Save Lives” project seeks to provide schoolchildren with BLS as early as possible in their education. Efforts must focus on educating the general public about the importance of CPR training and early use of an AED.⁴³⁻⁴⁵ Providing children with training is likely to be the only way of achieving sufficient national coverage in BLS competency. By implementing this type of initiative on a national level, we’ll be able to have, within a few decades, a national population fully trained in life-saving gestures, and thus maximize our chances of having effective witnesses.

## Strengths and limitations

This study had several limitations, including its internal validity and comprehensive dataset. During a 12-year period, more than 150,000 all-cause OHCAs have been recorded in the RéAC

database. A low proportion of missing data was guaranteed by the various quality controls implemented at the local dispatch centers and at the national level. To the best of our knowledge, the present study is the first in France to have examined the relationship between bystander status and OHCA cases.

The study also had some limitations. The study data were collected retrospectively, and certain confounding variables might not have been accounted for fully. Secondly, the study focused solely on the relationship of the first bystander and the patient, without considering the actions potentially taken by other bystanders. Future research should explore the influence of specific interventions performed by different types of bystander, in order to gain a more comprehensive understanding of the relationships with survival outcomes. Lastly, our study included pre-hospital care but not consider post-resuscitation care, it can affect the survival rates.
## Conclusion

In a nationwide study conducted in France, the CPR rate and clinical OHCA outcomes varied with the type of bystander. The presence of a family member as the first bystander was associated with a lower 30-day survival rate. Although family members tend to initiate resuscitation more frequently over the years, this is not associated with increased survival. Our findings emphasize the need for targeted interventions, including education and training programs for the general public.

## CRediT authorship contribution statement

**Hizia Benkerrou:** Writing – original draft, Methodology, Formal analysis, Conceptualization.
**Marguerite Lockhart:** Writing – review & editing, Validation, Methodology, Investigation.
**Matthieu Heidet:** Writing – review & editing, Validation, Investigation.
**Ramy Azzouz:** Writing – review & editing, Investigation, Formal analysis.
**Christian Vilhelm:** Writing – review & editing, Validation, Software, Investigation, Data curation.
**Hervé Hubert:** Writing – review & editing, Supervision, Methodology, Investigation, Data curation, Conceptualization.
**Morgan Recher:** Writing – review & editing, Supervision, Methodology, Investigation.
**Valentine Baert:** Writing – review & editing, Validation, Supervision, Methodology, Formal analysis, Data curation, Conceptualization.

## Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

## Acknowledgement

The French National Cardiac Arrest Registry is funded by the French Society of Emergency Medicine (SFMU), the Fédération Française de Cardiologie (FFC), Lille University, the Hauts-de-France Regional Council, and (via the European Regional Development Fund) the European Union.

The members of the French National Out-of-Hospital Cardiac Arrest Registry study group are Drs. Diego Abarrategui, Mohamed Abdeljaouad, Sami Abdelkhalek, Lila Abdelli, Romain Adam, Fabrice Agbemebia, Jean marc Agostinucci, Terence Ahui, Tesnim Aiouaz, Bassem Al afandi, Sara Al hassnaoui, Anas Al tabchi, Pierre Alba, Fabrice Alcouffe, Elodie Allemandet, Mona Allers, Camille Almeras, Yohan Altervain, Francois-Xavier Amelon, Eryk Amiens, Loic Amizet, Antoine Andre, Fanny Andre, Paul Andregnette, Florian Andriamiarado, Bastien Anette, Pierre andre Anizan, Celia Antonic-Ravaut, Jerome Antouard, Aurelie Armand, Aurelie Arnaud, Gaelle Arnaud, Idriss Arnaudet, Xavier Arrot, Gaele Aubert, Raphael Aubert, Antoine Aubrion, Thomas Audra, Claudie Audrain, Yannick Auffret, Harold Auger, Isabelle Aune, Jean-Christophe Auneau, Aurelie Avondo, Sonia Ayllon-Milla, Thierry Babet, Clement Babin, Florence Bages-Limoges, Salamata Bah assoumani, Haytam Bahaj, Anne Baina, Julien Baleine, Joseph Balland, Celine Ballet, Claire Ballet, Pierre Banwarth, Christian Bar, Patrick Barandiaran, Virginie Barbe, Christophe Barberis, Adele Barbery, Romain Bardelay, Philippe Bargain, Ruxandra Barrault, Morgane Barret, Benjamin Barry-Colin,

Francois-Xavier Barthelemy, Jean-Claude Bartier, Karen Barukh, Marielle Basty-Ghuysen, Martin Bataille, Marine Baudin, Stan Bawejski, Cyril Bazzoli, Placido Beaka, Max Beal, Adeline Beaudoin, Zaher Bayni, Sarah Bedini, Aurelie Begaudeau, Julien Beharelle, Niloufar Behechi, Matthieu Belin, Marielle Bellet, Marie-Camille Belli, Tobola Bellow, Bruno Belpeche, Josiane Benaniba, Ouassim Benaouali, Amandine Benard, Imane Benaziz, Sylvain Benenati, Yony Benguigui, Clement Benoit, Lucie Bensalah, Cecile Berard, Julie Berger, Patricia Bernadet, Sandra Bernard, Emmanuel Bernigaud, Antoine Berthelon, Frederic Berthier, Hedi Bertille, Benoit Bertrand, Pascale Bertrand, Philippe Bertrand, Sylvie Besnier, Paulin Besserve, Veronique Beunas, Roland Bianchi, Laurianne Billier, Cecilia Billiou, Tania Bintener, Pascal Bissolokele, Stephane Blain, Gilles Blaquiere, Romain Blondet, Emmanuel Blottiaux, Yann Bochard, Angele Boet, Clio Bohler, Rozenn Bois, Jennifer Bois-De-Fer, Romain Bokobza, Maxime Bollani, Cecile Bonhomme, Lucie Bonnet, Pierre-Francois Bonnet, Daniel Bonnieux, Jeremy Bontemps, Guillaume Boon, Juliane Bosc, Severine Boucard, Celia Bouchel, Olivia Boudard, Noura Boudeau-Zohair, Philippe Bouffard, Stephane Bougon, Emmanuel Bouhey, Guillem Bouilleau, Benjamin Bouinoue, Bertrand Boulanger, Chloe Boulanger, Guillaume Boulestein, Nadia Bourayou, Marike Bouret, Arthur Bourg, Anna Bourreau, Marion Boursier, Catherine Boussarie, Florent Bouteloup, Celia Boutin, Celine Boutry, Simon Bouvier, Romain Boyer, Cecile Bracq, Fabienne Branche, Camille Brandolin, Francois Brau, Mathieu Brazy, Stephanie Bredel, Samia Breggeon, Apolline Briatte, Nicolas Briole, Etienne Brisson, Romain Brocheux, Lara Brosset, Lucile Bruere, Amandine Bruneau, Romain Brunschwig, Laure Brus, Cecile Bujon, Clement Buleon, Laura Buscaglia, Olivia Busi, Geraldine Butin, Laurent Cabanne, Camille Cahuzac, Dominique Cailloce, Charles noel Camard, Leila Camboni-Pineau, Guillaume Campagne, Guilain Campan, Valentine Canon, Florian Canu, Olivier Capel, Georges-Antoine Capitani, Pierre Caprini, Elvira Capuano, Christophe Caralp, Maud Carcaille, Marion Caresmel, Olivier Carle, Alain Carreres, Chloe Carruesco, Alexis Casalonga, Denis Casanova, Margot Cassuto, Francois Castera, Sophie Cathelin, Pierre Catoire, Vincent Cattin, Pascale Cavalli, Martin Cellierer, Pascal Cendrie, Margaux Chabannon, Ascelene Chabaud, Fabien Chadelaud, Anne Champenois, Vanessa Champenois, David Chanel, Gauthier Chantrel, Anais Chapelle, Juliette Chapon, Amelie Charbon, Adeline Chardin, Yannick Charifou, Alexandre Charney, Carine Chassery, Coralie Chassin, Guillaume Chatenet, Arthur Chatrenet, Celine Chauveau, Claude Cheminat, Anne sophie Chesneau, Marine Chesnoy, Guillaume Chevrier, Eric Chiale, Julien Chiche, Mahado Chirwa, Marion Cholley, Hendricks Chomono, Laure Chopard, Pierre-Amaury Chopinaud, Mikhael Chouraqui, jean francois Cicala, Philippe Ciocca, Khadidiatou Cissokho, Emmelyne Clauw, Maxens Clauzel, Bonnet Clementine, Berenice Cluzel, Pierre Coffin, Rudy Cohen, Mauro Coletta, Valery Collet, Amandine Collin, Pierre-Etienne Colot, Camille Colson, Pascal Conan, Alice Conio, Loik Connan, Lucile Constant, Samuel Constant, Vincent Coppin, Carole Cornaglia, Mathieu Cornuault, Laure Corradi, Melanie Corre, Alexandra Corsia, Clemence Cosnard, Aurelie Costa, Yolaine Coses, Charlotte Cotronis, Bastien Coulon, Camille Coulon, Hubert Courcoux, Cecile Couteux, Sylvain Crindal, Maximilien Cruc, Clarysse Crusoe, Anne dominique Curunet-Raoul, Emelyne Cwicklinski, Alain Cys, Sami Dabbagh, Amira Dabri, Ludovic Daby, Sandra Daeron, Elodie Dagoret, Christian Daguerre, Antoine Daisey, Xavier Daligaud, David Dall acqua, Amelie Danet, Marie soline Danhiez, Dizae Dansou, Coralie Dassonville-Decaudin, Alix Dattin, Geoffroy David, Morgane
David, Olivier David, Sandy David, Serrano David, Camille Davost, Qientn De belizal, Philippe De boerio, Hugo De carvalho, Laurene De dinechin, Helene De facq, Marie alix De schlichting, Aurelien Debelle, Eric Deberdt, Sandra Decker, Julie Delcitre, Alice Decoster, Marie-Pierre Degos, Marc-Antoine Dehouck, Sophie Delage, Cyril Delangue, Hubert Delarue, Catherine Delattre, Thomas Delatre, Julie Delaunay, Marine Delbergue, Marc Delbos, Amelie Delcourt, Thibault Delemar, Romain Delespierre, Stephanie Deleu, Amel Delli, Thierry Delmas, Adrien Delprat, Ingrid Demarle, Adelaide Denoel, Geoffroy Denoray, Audrey Derigent, Melanie Desangles, Nicolas Desaveines, Claire Desbuard, Jean-Philippe Desclefs, Benoit Deslais, Segolene Desoubeyran, Marie Desroziers, Arnaud Dessaint, Anne-Laure Dessoy, Florian Deuez, Arnaud Devillard, Stephane Dhalluin, marion Dhers, Christophe Dhote, Hassen Didane, Olivier Diez, Francois Dissait, Lynda Djebbar, Baptiste Dobanton, Beatrice Doco, Sandrine Dojat, Benedicte Douay, Jimmy Douay, Mathieu Doukhan, Samia Draoua, Cisse Drosseau-Philippe, Matthieu Drouard, Marie Druet, Marc du Besset, Josephine Dubeaux, Manon Dubernat, Camille Dubois, Marie Dubourg, Nicolas Dubujet, Pierre Ducasse, Jonathan Duchenne, Caroline Duchier, Antoine Duconge, Yves Duffait, Sebastien Dufraise, Edouard Dugat, Franck Dumas, Jean-Baptiste Dumont, Nathalie Dumont, Julie Dumouchel, Yann Duperron, Aurelie Dupin, Erwan Dupire, Murielle Dupont, Thomas Dupuy, Marion Durand, Olivier Durand, Alice Durand-Perdriel, Emilie Durieux, Sebastien Dussoulier, Benoit Duval, Emmanuel Duval, Nicolas Duytsche, Mohamed Dyani, Malek Echeikh, Claire Edange, Gerald Egmann, Sebastien Ehrminger, Mounir El abdi, Imane El kadiri, Ugo Ellena, Vilbois Emmanuel, Anne Emonet, David Emsallem, Aurore Ernu, Josephine Escutnaire, Vincent Etienne, Yoann Evain, Gregoire Evrard, Caroline Faivre-Pierret, Aurelie Faldard, Armelle Fanchon, Guillaume Fatscher, Zoe Faure, Laura Federici, Lise Fehner, Meriem Ferhati, Martin Ferquel, Juliette Ferre, Justine Ferreira, Anne laure Ferri, Guillaume Ferrier, Jean-Baptiste Fezard, Nasri Fiani, Marie Laurence Fievet, Olivier Fillatre, Lucas Flamant, Maud Flambard, Marie Flandinette, Elodie Flauder, Thomas Fleuchot, Kleeve Fleurival, Amandine Fleury, Noel Florent, Jonathan Florentin, Bertin Fogang, Maxime Foiret, Julien Foly, Alban Forel, Lahcene Foudi, Helene Foulgoc, Emmanuelle Fournier, Marc Fournier, Philippe Fradin, Virginie France, Herve Frances, Marie Frei, Alexis Fremery, Regis Frenais, Louis Fresse, Jerome Frey, Emmanuelle Fritsch, Isaure Fromont, Dora Furnon, Celine Fuseau, Patrick Fuster, Romain Futin, Keller Gabriel, Matthieu Gaget, Florence Gaillard, Nancy Gaillard, Michel Galinski, Eva Gallais, Michel Gallon, Veronique Galtier, Thierry Gamin, Pauline Gantois, Zahia Gaoui, Emilie Garay, Aurelien Garcia, Carolina Garcia, Lea Garcia, Franck Garden breche, Matthias Garidou, Claire Gast, Patrick Gatin, Julien Gaubert, Vincent Gauclere, Anais Gaufrer, Lise Gautier, Julien Gay, Sylvain Geffroy, Emilie Gelin, Anne-Sophie Genain-Soulier, Sarah Gendraud, Paul-Henri Gendre, Stephane Gennai, Angelie Gentilhomme, Benoit Genuyt, Aurelien Gerard, David Gerault, Fanny Gervais, Renaud Getti, Vincent Gevrey, Nawel Gharnaout, Louise Giaume, Arnaud Gille, Gille Gille, Stephane Gillet, Lucie Ginoux, Cecile Girard, Sabrina Giraud, Fabrice Girault, Alexandra Givernaud, Guillaume Gnyp, Frank Goes, Mathieu Goichon, Adrien Goldstein, Charles Gomes de mattos, Coralie Gondret, Corinne Gonet-Dubois, Denis Gonzalez, Geraldine Gonzalez, Lola Gonzalez, Marion Gornet, Pierre Gosset, Christine Goubet potiron, Julie Gouges, Nathalie Goulois, Virginie Goulvin, Melanie Goument, Claire Gradel, Cyril Grandjon, Sarah Grar, Charlene Grand, Cecile Graux, Eric Grave, Fabrice Gregoire, Jl Greingor, Gauthier Gress,

Emma Grigahcine, Oceane Grignon, Aude Grigoletto, Philippe Gripon, David Grua, Annaig Guegan, Pierre-Alban Guenier, Magali Guerin, Thomas Guerin, Hubert Gueriot, Carole Guery, Charlene Guez, Victor Guigon, Durand Guillaume, Frederic Guillaumee, Marion Guillemin, Aline Guillet, Alain Guillon, Philippe Guillot, Sollweig Guinard, Noutoa Guindo, Olivier Guiot, Adrien Habay, Laurent Halbout, Gabriel Hamadi, David Hamdan, Kheir-Eddine Hamdi, Najat Hammouti, Tom Handwerk, David Harel, Alexa Harguindeguy, Laure Harle, Gaelle Haziza, Manon Hebrard, Christine Hecker, Karina Heleniak, Meriem Hellal, Ihsene Henane, Florent Henin, Jonathan Hennache, Raymond Henry, Thomas Hereng, Laurent Herkelmann, Gilles Hernandez, Aurelien Herpin, Virginie Heydel, Johanna Higginson, Pascale Hiller, Timothee Hiriart, Stephanie Hoareau, Julie Hoff, Laure Hoffman, Eric Hollecker, Arthur Honorez, Ingrid Horuckowa, Nicolas Hourdin, Vanessa Houze-Cerfon, Julien Hrasko, Priscilia Hsing, Loic Huet, Delphine Hugenschmitt, Thomas Hullin, Noemie Hurst, Amr Ibrahim, Pauline Inglada, Line Jacob, Renaud Jacquemin, Deborah Jaeger, Laure Jainsky, Guillaume Jammes, Benoit Jardel, Coline Jaud-Fischer, Charline Jauneau, Francois Javaudin, Yoann Jeanmasson, Joel Jenvrin, Alexandre Jeziorny, Guillaume Joannesse, Marie Jobert, Geraldine Joliet, Arnaud Jollet, Marc Joly, Sebastien Jonquet, Romain Jovelin, Fabien Joyard, Ignasi Jubert, Mathilde Jung, Roger Kadji, Jean-Philippe Kahn, Isabelle Kaliszczak, Mariam Kamara, Mounir Kamboua, Clotilde Kamga, Cyrille Kamga, Claire Kany, Christian Kassasseya, Elodie Katz, Romain Kazmierczak, Helene Kermorgant, Cecile Kernaleguen, Mounir Khiter, Caroline Kindle, Sebastien Kirsch, Amelie Klein, Stephane Klimas, Vincent Kottmann, Etienne Kras, Tarek Kribeche, Vincent Kuczer, Franck Labarrere, Benedicte Labbens, Stephane Labed, Francois Xavier Laborne, Anne Laboure, Melanie Lacaze, Julien Lacoste, Arnaud Lacroix, Marina Lafay, Blandine Lafitte, Jean Lafon, Armelle Lafontaine, Martin Lafrance, Steven Lagadec, Kelly Laggia, Martine Lagier, Sana Lahmar, Xavier Lakermance, Sara Lakhal, Jessica Lalande, Yacine Lamarche-Vadel, Elisa Lamazou, Christophe Lambert, Julia Lambert, Theo Lambropoulos, Marion Lamothe, Charles Lamourere, Michael Lamy, Pascale Lamy, Virgine Lancon, Yankel Landau, Alice Landel, Frederick Langeron, Mathilde Lannes, Melanie Laot, Anne claire Laquerbe, Elodie Larchanche, Fanny Larcher, Manon Lartaud, Thomas Laterrade, Gwendoline Latournerie, Audrey Launay, Paris Laurenne, Adrien Lauvray, Loic Lavaill, Jeanne Lavielle, Edouard Laville, Julien Lazar, Victor Lazard, Celine Le beuan, Aurelie Le goff, Arnaud Le jan, Etienne Le joubloux, Thomas Le normand, Olivier Le pennetier, Philippe Le pmpec, Thomas Le, Antoine Lebail, Cecile Lebrun, Nathalie Lecadet, Aurelie Lechevrel, Gilles Leclerc, Maxence Leclerc, Sylvain Leclere, Romain Lecomte, Julien Lecoz, Aurelien Leduc, Cyndie Lefebvre, Dominique Lefebvre, Stephanie Lefeuvre, Nathalie Lefevre, Antoine Leforestier, Alexandra Lefort, Delphine Lefranc, Valentin Lefrancois, Lea Legay, Estelle Legeard, Kevin Legendre, Gregory Legrand, Cathelle Lemarchand, Remy Lemarchand, Claire Lenne, Laurence Lepage, Alexandra Lepeve, Anne-Laure Lepori, Thierry Leraitre, Stephane Lere, Pierre Leroux, Antoine Leroy, Heloise Leroy, Julien Lesaca, Christine Lespiaucq, Jean yves Letarnec, Emilie Letourneur, Gregory Letur, Pascale Leurent, Marion Leveau, Brice Levelu, Eleonore Levet, Pascaline Levrard, Patrick Levy, Raffaello Li crapi, Jean Limery, Caroline Line, Sebastien Line, Laura Lis, Laetitia Livernois, Mathilde Loirat, Sara Lomberty, Celine Longo, Lea Loquet, David Lorain, Sarah Lorge, Marine Loridon, Thomas Lory, Yannick Loslier, Solene Loth, Richard Loubert, Aurelie Louchet, Jean-Paul Lougnon, Stephanie Louisot, Alexandre Lozano, Marie Loze, Anne sophie Lucas, Remy
Lucas, Yannick Macabre, Camille Machet, Edouard Magimel-Pelonnier, Sandy Mahauden, Aurore Mahe, Zakaria Mahi, Olivier Maigre, Michel Maille, Gwenaelle Majoufre, Gilles Majour, Domitille Malange, Anne-Sophie Malaquin, Arnaud Malbranque, Nadia Mansouri, Bruno Maquaire, Pierre Marais, Jean-Baptiste Marc, Pauline Marchand, Sebastien Marchasson, Joelle Marchegay, Jacques Marchi, Julien Mariage, Dubois Marina, Heloise Marinoni, Paul Marteix, Faycal Marrakchi, Jerome Martin, Paul Louis Martin, Thibault Martin, Arnaud Martinage, Nathalie Mascarenc, Sylvie Massacrier, Juliette Masse, Solene Masse, Caroline Masson, Loic Masson, Melanie Mathe, Clement Mathie, Benedicte Mathieu, Kleber Mathilde, Laure Maugein, Marion Maurel, Laure Maurice, Lionel Maville, Sophie May, Guillaume Mazetier, Andre Mazille, Margherita Mazzoldi, Fatima Mbarki, Marie Fleur Megard, Oussama Megherbi, Isabelle Megy-Michoux, Eric Meinadier, Laure Melin, Marion Menay, Pascal Menot, Elise Menu, Elsie Menu, Catherine Mercier, Fatima Merghem, Heloise Merle, Adil Mesli, Caroline Mesplede, Alexis Mesieux, Jacques Metzger, Juliette Meunier, Stephanie Meunier, Daniel Meyran, Laurianne Michelland, Corinne Michenet, Sandrine Michenet, Guilhem Milhaud, Audrey Millot, Frederic Minko, Jerome Minost, Julie Miquelestorena, Celine Miranda, Albrice Moine, Linda Moine, Christelle Molet, Claudine Molly, Jean-Baptiste Monange, Franck Monchard, Martine Moneron, Thomas Monneret, Melanie Monribot, Francois-Xavier Montagnon, Emmanuel Montassier, Romain Moquay, Alice Morat, Emanuel Moren marechal, Jean-Charles Morel, Paola Morel, Maria elena Morel maestre, Fanny Moulinet, Valerie Mozzi, Alain Mpela, Johanna Mroueh, Uriel Munoz, Sebastien Mur, Davy Murgue, Margaux Muteaud, Marie Naban, Bertille Naegels, Sophie Narcisse, Jean ely Nardy, Julien Naud, Florence Naux, Sophie Nave, Rachel Ndimba, Florian Negrello, Mohamed Nekkaz, Eloi Nenert, Yves marie Ngonga, Natacha Ngoyi, Arsene Nguessan, Kim Nguyen, Ophelie Nicolats, Leandre Nicolin, Audrey Nigou, Claire-Marie Nivet, Sarah Nixdorf, Magaly Noel, Camille Nussbaum, Mathieu Oberlin, Kirill Oganov, Stephanie Olive, Larissa Oliveira, Johann Olivier, Rodolphe Orange, Francois Orcival, Frederic Orhon, Gerard Oriot, Jennifer Ospital, Maud Outrequin, Younes Ouyachchi, Mariane Ovtcharenko, Philippe Pamart, Agathe Pancher, Marc antoine Pangallo, Pamini Panharen, Gregory Pansin, Francois Pantaloni, Annelaure Paquet, Rahman Paquirimoidine, Xavier Paringaux, Benoit Paris, Laurenne Paris, Sarah Parisot, Pierre Parsis, Clemence Pascalon, Nicolas Pauchet, Serge Paula palma, Laure Pavageau, Laurent Pecout, Julien Pegeot, Vincent Pegoraro, Aurelie Pegorier, Olivier Peguet, Brandon Peixoto, Marion Pellerin, Elodie Pelletier, Claudia Pelsy, Tanguy Peluchon, Yann Penverne, Oceane Pernin, Thomas Pernot, Florian Prawald, Philippe Pes, Caroline Petit, Olivia Petitdemange, Etienne Petitdidier, Martin Petitprez, Oceane Pettinotti, Sylvie Peyrat, Ludovic Piboule, Daniel Pic, Jeanne Picart, Mailis Piccardi, Dorine Pichon, Jessica Picot, Gil Pierre, Ambre Pignol, Natacha Pilati, Virginie Pinaud, Flore Pineau, Lauren Pinel, David Pinero, Marina Pinto, Camille Pioch, Sarah Pires, Perrine Planet, Cecile Plenier, Elodie Pocholle, Fabien Poher, geraldine Poincet, Sebastien Poincet, Delphine Pointaire, Christian Poirel, Stephanie Polini, Nathalie Polisset, Soisic Pommier, Lucile Ponties, Stephane Potriquier, Jeremie Poulet, Patrick Poupart, Thomas Poussot, Catherine Pradeau, Anne-Lise Pradel, Nicolas Pradignac, Marion Precigout, Jean-Baptiste Pretalli, Sophie Prieur, Stevens Prineau, Christina Prouve, Florence Prudor, Aurelien Puchois, Thomas Quibel, Dominique Quilliet, Mathilde Quinty, Maria

Rachidi, Julien Raconnat, Dorothee Radenac, Raphaelle Rahmani, Jean-Louis Rakotonirina, Martin Rallu, Thierry Ramaherison, Noel Ramaniraka, Solo Randriamalala, Jocelyn Rapp, Camille Raynaud, Olivier Rebet, Laurent Rebillard, Claudine Remakel, Annabelle Remond, Serge Renault, Emilie Resplandy, Francois Revaux, Franck Reydy, Yassine Rharif, Agnes Ricard-Hibon, Ghislain Richard, Eleonore Riff, Isabelle Riom, Jean-Dominique Risser, Robert Ristovski, Jean-Christophe Robart, Elise Robeley, Damien Robert, Frederique Robert, Helene Robert, Samuel Robert, Florent Roche, Annabelle Rocheteau, Pierre Rodriguez, Juliette Rogersename, Pierre-Julien Rogez, Jerome Rojas, Chloe Roland, Didier Roland-Billecart, Julie Rosenblatt, Yann Roth, Julie Rotival, Nicolas Roucaud, Nathalie Roudiak, Christelle Rouet, Louis Rouffilange, Jean Rouffineau, Jimmy Rouquet, Matthieu Rousselet, Charlotte Rousselon, Nicolas Roux, Celine Royer, Guillaume Roze, Gautier Ruellan, Solene Ruiz, Phloy Rungsawad, Laure Saada, Sebastien Sabbat, Sonia Sadoune, Benoit Sahuc, Amelie Saint paul, Stephane Saintonge, Beatrice Salaun, Cyril Salazar, Julie Salignon, Elodie Salvador, Marie San miguel, Caroline Sanchez, Oriana Sanchez, Chantal Sanjuan, Aurelie San-Miguel, David Sapir, Jean-Louis Saucede, Irina Sauder, Geraldine Sauvaget, Jean-Remy Savineau, Alexandru Savu, Jasmine Sawadogo, Michel Scherpereel, Thibault Schillig, Anne catherine Schmit, Valerie Schmitt, Sophie Schvahn, Christelle Sciacca, Pierre Scuotto, Salim Sebai, Julien Segard, Lionel Segard, Gerald Sejourne, Alienor Senez, Patrice Serre, Marine Serres, Julian Serrurier, Laura Seyrat, Marta Sigarteu, Antoine Sigaux, Simone Silvestri, Isabelle Simeon, Ciprian Simisd Dean, Benoit Simon, Bruno Simonnet, Allison Singier, Perrine Sobocinski, Lea Soucheleau, Mihedja Soulaimana, Marie Soulat, Audrey Spriet, Sophie Staes, Laurence Steenbeke, Virginie Stefanski-Serniclay, Ralitsa Stoeva, Teddy Sturiale, Pauline Suhas, Myriam Sussat, Mohammed Sy, Roux Sylvie, Eric Sztil, Trung hung Ta, Julien Tabarly, Romain Tabary, Pierre-Emmanuel Tabourin, Bertrand Tahon, Christelle Tancoigne, frederic Tasei, Victor Tasteyre, Samuel Taxis, Jean francois Techer, Eric Tellier, Robin Tellier, Eric Tentillier, Lucie Teysier, Brejoux Theo, Odile Theurey, Eric Thibaud, Klein Thibaut, Michel Thicoipe, Marina Thiefin, Romain Thiriat, Sylvain Thiriez, Agnes Thivellier, Fabien Thomas, Marie Thomas, Jean-Sebastien Top, Florian Torerton, Emma Toucas, Karim Toumert, Cedric Touquet, Eve Trebouet, Justine Treels, Sarah Laure Trialoup, Bruno Trogoff, Helene Trouvain, Paulin T hisumbule, Veronique Uchlinger, Cecile Ursat, Guillaume Ursat, Laurent Valentin, Rishad Vally, Elyse Valser, Myriam Van tricht, Gregory Vancoillie, Carine Vanderstraeten, Ludivine Vanparys, Paul Vara, Laurene Vasseur, Isabelle Vassor, Myriam Vauchez, Amelie Vaudelin, Pierre-Olivier Vautrin, Laetitia Velly, Valentinne Vendois, Laurent Vercher, Guillaume Verge, Sophie Vergely, Muriel Vergne, Vanessa Verhaeghe, Stephanie Verissimo, Celine Vermersch, Jean pierre Vernet, Gregoire Versmee, Michael Vial, Marie-Sophie Viallard, Marie Viciana, Guillaume Vidal, Elodie Vidil, Frederic Vignaud, Claire Vigneau, Laurent Villain-Coquet, Maxime Villard, Barbara Villoing, Rayane Vincent, Mathieu Violeau, Clelia Viratelle, Loukas Vytiniotis, Corinne Wassong, Olivier Watrelot, Melanie Watremez, Eva Weinzorn, Claire marie Weyer, Marc Witte, Florine Wojcieszak, Marion Wrobel, Vassilis Wurtz-Gress, Geoffrey Wyckaert, Samraa Yahiaoui, Matthieu Yali, Quentin Yvetot, Guillaume Zamparini, Achraf Zariouh, Thibault Zelmanski, Maria Zemouri, Badia Zeribi, Laila Zitouni
# Appendix A. Supplementary material

Supplementary data to this article can be found online at https://doi.org/10.1016/j.resplu.2024.100858.

## Author details

on behalf of the GR-RéAC<sup>b</sup> <sup>a</sup>Univ. Lille, CHU Lille, ULR 2694 - METRICS: Évaluation des Technologies de santé et des Pratiques Médicales, F-59000 Lille, France <sup>b</sup>French National Out-of-Hospital Cardiac Arrest Registry, RéAC, F-59000 Lille, France <sup>c</sup>Pediatric Intensive Care Unit, CHU Lille, F-59000 Lille, France <sup>d</sup>Assistance Publique - Hôpitaux de Paris (AP-HP), SAMU 94 et Urgences, Hôpitaux Universitaires Henri Mondor, F-94000 Créteil, France <sup>e</sup>Université Paris-Est Créteil (UPEC), EA-3956 (Control in Intelligent Networks, CIR), F-94000 Créteil, France <sup>f</sup>Centre Antipoison et de Toxicovigilance de Lille, CHU Lille, F-59000 Lille, France

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