Valentine Canon

Deborah Jaeger

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Claire-Marie Weyer

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Claire Marie

Assessment of changes in cardiopulmonary resuscitation practices and outcomes on 1005 victims of out-of-hospital cardiac arrest during the COVID-19 outbreak: registry-based study

Keywords: COVID-19, Registry, Out-of-hospital cardiac arrest, Resuscitation

de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

Introduction

The current SARS-CoV-2 outbreak is leading to a reorganization of healthcare systems to limit as much as possible virus spread. Emergency medical systems must constantly adapt while coping with overloaded emergency departments, and severe working conditions [START_REF] Garcia-Castrillo | European society for emergency medicine position paper on emergency medical systems' response to COVID-19[END_REF]. The primary measures are based on population isolation, physical distancing and personal protective equipment (PPE) use. The virus is transmitted mainly by direct contact or droplets [START_REF] Rothan | The epidemiology and pathogenesis of coronavirus disease (COVID-19) outbreak[END_REF] from symptomatic or nonsymptomatic infected persons [START_REF] Bai | Presumed asymptomatic carrier transmission of COVID-19[END_REF]. Outside the current viral outbreak, cardiopulmonary resuscitation (CPR) is not considered a frequent source of infectious disease transmission (estimated at < 1/200,000) [START_REF] Mejicano | Infections acquired during cardiopulmonary resuscitation: estimating the risk and defining strategies for prevention[END_REF], however, close contact with a potentially infected subject, imposed by CPR, could be a source of SARS-CoV-2 contamination [START_REF] Christian | Possible SARS coronavirus transmission during cardiopulmonary resuscitation[END_REF][START_REF] Liu | Risk factors for SARS infection among hospital healthcare workers in Beijing: a case control study[END_REF]. The resuscitation guidelines, in force since 2015, have therefore been adapted to this new situation; e.g., for basic life support (BLS), mouth-to-mouth ventilation in addition to chest compression are recommended to bystanders [START_REF] Berg | Part 5: adult basic life support: 2010 American Heart Association guidelines for cardiopulmonary resuscitation and emergency cardiovascular care[END_REF][START_REF] Perkins | European resuscitation council guidelines for resuscitation 2015: section 2. Adult basic life support and automated external defibrillation[END_REF][START_REF] Couper | COVID-19 in cardiac arrest and infection risk to rescuers: a systematic review[END_REF]. For advanced life support (ALS), bag-mask or supraglottic airway (SGA) ventilation are considered acceptable alternatives to tracheal intubation [START_REF] Neumar | Part 8: adult advanced cardiovascular life support: 2010 American Heart Association guidelines for cardiopulmonary resuscitation and emergency cardiovascular care[END_REF][START_REF] Soar | Adult advanced life support section collaborators. European resuscitation council guidelines for resuscitation 2015: section 3. Adult advanced life support[END_REF]. Recently, updates have been issued, notably by the International Liaison Committee on Resuscitation (ILCOR) [START_REF] Perkins | International liaison committee on resuscitation: COVID-19 consensus on science, treatment recommendations and task force insights[END_REF], the Emergency Cardiovascular Care Committee, and the American Heart Association [START_REF] Edelson | Interim Guidance for Basic and Advanced Life Support in Adults, Children, and Neonates With Suspected or Confirmed COVID-19: From the Emergency Cardiovascular Care Committee and Get With the Guidelines®-Resuscitation Adult and Pediatric Task Forces of the American Heart Association in Collaboration with the American Academy of Pediatrics, American Association for Respiratory Care, American College of Emergency Physicians, The Society of Critical Care Anesthesiologists, and American Society of Anesthesiologists: Supporting Organizations: American Association of Critical Care Nurses and National EMS Physicians[END_REF]. Briefly, the main changes recommend that lay rescuers should consider chest compressions only (CO-CPR), except for children, and all life support providers should use PPE during resuscitation and favour early tracheal intubation to minimise aerosols. These changes, within the COVID-19 context, can impact the management of OHCA at each level (BLS and ALS). The purpose of our study was to compare the management of OHCA resuscitation by bystanders, first aid providers and mobile medical teams (MMT), between the COVID-19 outbreak period and a non-COVID-19 period.

Methods

Study setting

In France, the pre-hospital emergency medical system is two-tiered, with a fire department ambulance available for prompt intervention and BLS, and MMT for ALS [START_REF] Javaudin | Organisation of prehospital care: the French experience[END_REF]. The coordination of care for OHCA and other outof-hospital emergencies is under the responsibility of medical dispatch centres. All voluntaries MMT participating to the French OHCA registry (RéAC) use a specific intervention sheet for OHCA provided by the RéAC. The RéAC covers an at-risk population of about 20 million inhabitants. This RéAC recording form enables to collect patient data, times, care, and survival status. The RéAC form meets the requirements of the French Emergency Medical System (EMS) organization, and is structured according to the universal Utstein style [START_REF] Perkins | Cardiac arrest and cardiopulmonary resuscitation outcome reports: update of the utstein resuscitation registry templates for out-of-hospital cardiac arrest: a statement for healthcare professionals from a task force of the International Liaison Committee on Resuscitation (American Heart Association, European Resuscitation Council, Australian and New Zealand Council on Resuscitation, Heart and Stroke Foundation of Canada, InterAmerican Heart Foundation, Resuscitation Council of Southern Africa, Resuscitation Council of Asia); and the American Heart Association Emergency Cardiovascular Care Committee and the Council on Cardiopulmonary, Critical Care, Perioperative and Resuscitation[END_REF]. Data are reported in the secure RéAC database (www.registreac.org). During the outbreak period, RéAC users can record (database) if subjects are infected by COVID-19. A 30-day follow-up data collection after the OHCA or at the time of hospital discharge is performed and entered into the database. The whole functioning of the RéAC registry had previously been described [START_REF] Hubert | Rationale, methodology, implementation, and first results of the French out-of-hospital cardiac arrest registry[END_REF].

Study population and data

Our comparative multicentre study used data from the French national OHCA registry (RéAC). We compared two cohorts of OHCA victims, the first corresponded to OHCA occurred between March 1st and April 31st 2020, corresponding to the COVID-19 outbreak period, and the second corresponding to OHCA occurred between March-April 2019, i.e. the non-COVID-19 period. Our inclusion criteria were: all medical OHCA according to the Utstein template [START_REF] Perkins | Cardiac arrest and cardiopulmonary resuscitation outcome reports: update of the utstein resuscitation registry templates for out-of-hospital cardiac arrest: a statement for healthcare professionals from a task force of the International Liaison Committee on Resuscitation (American Heart Association, European Resuscitation Council, Australian and New Zealand Council on Resuscitation, Heart and Stroke Foundation of Canada, InterAmerican Heart Foundation, Resuscitation Council of Southern Africa, Resuscitation Council of Asia); and the American Heart Association Emergency Cardiovascular Care Committee and the Council on Cardiopulmonary, Critical Care, Perioperative and Resuscitation[END_REF]. Our exclusion criteria were: physical indication of death, patients with a known Do Not Attempt Resuscitation (DNAR) order, end of life patients, and traumatic drowning, overdose, asphyxia (external causes) and electrocution OHCA.

For COVID-19 affected-patients, probable or confirmed COVID-19 cases were identified in compliance with the World Health Organization (WHO) definition [START_REF]Global surveillance for COVID-19 caused by human infection with COVID-19 virus: interim guidance[END_REF]. Hence, probable cases corresponded to a suspected case for whom testing could not be performed for any reason, or for whom testing for COVID-19 was inconclusive. In our context, patients with symptoms (fever associated with respiratory symptoms or symptoms suggestive of COVID-19 at the MMT physician discretion) and confirmed cases (COVID-19 laboratory confirmation) were aggregated to the same group: COVID-19 OHCA.

Endpoints

Our study was based on management comparisons during the COVID-19 and non-COVID-19 periods. Firstly, the determinants of resuscitation undertaken by bystanders (CPR initiation, type of CPR, use of a defibrillator), secondly, the description of BLS made by the first aid providers (timing, use of ventilation and defibrillator), and lastly, ALS details performed by the MMT (timing, initiation of ALS, administration of epinephrine and tracheal intubation). The other endpoints were return of spontaneous circulation (ROSC) and the survival 30 days after OHCA or at hospital discharge (D30 survival).

Statistical analysis

We described and compared baseline characteristics, BLS and ALS of the two patient cohorts (COVID-19 and non-COVID-19 period). In the COVID-19 period, we compared COVID-19 patients and non-COVID-19 patients. The quantitative variables were described as mean and standard deviations. The qualitative variables were described as frequencies. Bivariate analyses were assessed estimating the between-group difference and its 95% confidence interval.

All statistical analyses were performed using SPSS software (version 25.0; IBM, Armonk, NY, USA). The threshold for statistical significance was set at p < 0.05.

Ethics

This study was approved as a medical registry assessment by the French Advisory Committee on Information Processing in Health Research (CCTIRS), and by the French National Data Protection Commission (CNIL, authorisation number 910946). This study was approved as a medical registry assessment without the requirement for patient consent.

Results

Patients

During the study periods, 3629 subjects were recorded in the RéAC registry, 1375 were recorded in March and April 2020 (COVID-19 period), and 2254 in March and April 2019 (non-COVID-19 period). We excluded 591 victims of non-medical OHCA, 278 patients with physical indication of death at MMT arrival and 135 patients with "do no attempt resuscitation instructions" or in end of life. Hence, 2625 subjects were included; 1005 were recorded during the COVID-19 period (Fig. 1). Among the 1005 subjects in the COVID-19 period, 197 patients (19.6%) were classified as COVID-19 OHCA.

Baseline patient descriptions and comparisons

As shown (Table 1), patient mean age was 68 ± 17 years and 75.5% of OHCA occurred at home. In terms of survival, 5.0% were alive at D30.

During the COVID-19 period, no demographic differences were observed regarding patient age, sex, and cardiovascular, respiratory or diabetes histories. However, ROSC and D30 survival were significantly lower (19.5% vs. 25.3%; difference, -5.8 percentage points [95% CI, -9.0 to -2.5]; and 2.8% vs. 6.4%; difference, -3.6 percentage points [95% CI, -5.2 to -1.9]; respectively).

Basic life support

In the total population, witnesses performed a BLS in 52.9% of cases, chest compression-only (CO-CPR) in 71.1% of cases, and chest compression with mouth to mouth (standard CPR, S-CPR) in 28.5% of cases (Table 2).

During the COVID-19 period, bystanders initiated BLS less often (49.8% vs. 54.9%; difference, -5.1 percentage points [95% CI, -9.1 to -1.2]), and the no flow duration (time between collapse and CPR initiation) was longer (15 ± 18 min vs. 12 ± 13 min; mean difference, 3.0 [95% CI, 1.8 to 4.2]). No differences were observed between the rate of CO-CPR and S-CPR, and the use of automated external defibrillators (AED).

During both study periods, first aid providers arrived in 12 ± 10 min on OHCA scenes, and performed BLS in 87.0% of cases. A defibrillator was used in 71.0% of cases, and a shock was delivered to 17.3% of subjects.

During the COVID-19 period, the time between T0 (the call to emergency services) and first aid provider arrival was slightly longer (12 ± 11 min vs. 11 ± 9 min; mean difference, 1.0 [95% CI, 0.0 to 2.0]). BLS was ). However, when a BLS was implemented, no differences were observed for chest compression and bag-mask ventilation rates.

Advanced life support

The mean MMT arrival time was 22 ± 15 min, time to tracheal intubation was 28 ± 13 min, and time to adrenaline injection was 26 ± 12 min. ALS was started in 72.0% of cases (Table 3).

No differences between the two periods were observed for ALS timing or duration. ALS was less frequently implemented during the COVID-

Discussion

From a French OHCA prospective cohort, we assessed the impact of the COVID-19 outbreak on CPR practices (BLS and ALS). We observed that BLS and ALS initiation was less frequent during the COVID-19 period (whether the subjects were suspicious of COVID-19 or not). The ROSC rate was reduced by six points and D30 survival was halved during the COVID-19 period, when compared to the non-

BLS by bystanders

During the COVID-19 outbreak period, we observed a lower rate of bystander CPR initiation. This could be explained by the fear of contracting SARS-CoV-2 infection. Scquizzatoa et al. warned of the need to initiate resuscitation as early as possible following an OHCA incident in Sydney, Australia, where bystander CPR was not initiated on a 60-year-old Chinese man for fear of infection with the coronavirus [START_REF] Scquizzato | The other side of novel coronavirus outbreak: fear of performing cardiopulmonary resuscitation[END_REF]. Indeed, initiating early CPR is key to successful outcomes [START_REF] Group | Cardiopulmonary resuscitation by bystanders with chest compression only (SOS-KANTO): an observational study[END_REF][START_REF] Hasselqvist-Ax | Early cardiopulmonary resuscitation in out-of-hospital cardiac arrest[END_REF]. For adults, CO-CPR appears to be a good alternative to standard CPR (including mouth-to-mouth ventilation) in this context. The meta-analyses of three randomised studies comparing S-CPR to CO-CPR, showed that CO-CPR was associated with improved survival [START_REF] Zhan | Continuous chest compression versus interrupted chest compression for cardiopulmonary resuscitation of nonasphyxial out-of-hospital cardiac arrest[END_REF][START_REF] Hüpfl | Chest-compression-only versus standard cardiopulmonary resuscitation: a meta-analysis[END_REF]. Recent observational studies have shown either equivalent or improved outcomes of CO-CPR [START_REF] Kitamura | Chest compression-only versus conventional cardiopulmonary resuscitation for bystander-witnessed out-ofhospital cardiac arrest of medical origin: a propensity score-matched cohort from 143,500 patients[END_REF][START_REF] Iwami | Dissemination of chest compressiononly cardiopulmonary resuscitation and survival after out-of-hospital cardiac arrest[END_REF][START_REF] Riva | Survival in out-of-hospital cardiac arrest after standard cardiopulmonary resuscitation or chest compressions only before arrival of emergency medical services: Nationwide study during three guideline periods[END_REF]. However, for children with OHCA, it would appear that S-CPR is associated with a better prognosis than CO-CPR [START_REF] Zhang | Chest-compression-only versus conventional cardiopulmonary resuscitation by bystanders for children with out-of-hospital cardiac arrest: a systematic review and meta-analysis[END_REF]. The latest updated recommendations support this, i.e. CO-CPR for adults and S-CPR for children during the COVID-19 outbreak period [START_REF] Edelson | Interim Guidance for Basic and Advanced Life Support in Adults, Children, and Neonates With Suspected or Confirmed COVID-19: From the Emergency Cardiovascular Care Committee and Get With the Guidelines®-Resuscitation Adult and Pediatric Task Forces of the American Heart Association in Collaboration with the American Academy of Pediatrics, American Association for Respiratory Care, American College of Emergency Physicians, The Society of Critical Care Anesthesiologists, and American Society of Anesthesiologists: Supporting Organizations: American Association of Critical Care Nurses and National EMS Physicians[END_REF]. To further reduce the viral transmission risk, it is suggested that the rescuer and the patient both wear masks or cloths if possible [START_REF] Edelson | Interim Guidance for Basic and Advanced Life Support in Adults, Children, and Neonates With Suspected or Confirmed COVID-19: From the Emergency Cardiovascular Care Committee and Get With the Guidelines®-Resuscitation Adult and Pediatric Task Forces of the American Heart Association in Collaboration with the American Academy of Pediatrics, American Association for Respiratory Care, American College of Emergency Physicians, The Society of Critical Care Anesthesiologists, and American Society of Anesthesiologists: Supporting Organizations: American Association of Critical Care Nurses and National EMS Physicians[END_REF].

In the OHCA event, rapid access to a defibrillator is essential for an early ROSC and survival [START_REF] Kitamura | Public-access defibrillation and out-ofhospital cardiac arrest in Japan[END_REF]. During the COVID-19 period, bystanders frequently used defibrillators despite the closure of some public places. Access to defibrillators has been maintained during this lockdown. Moreover, cardiac arrests occurred more frequently at home, where access to defibrillators were limited. The recent development of smartphone applications for locating defibrillators in public places and requesting citizen responders to provide CPR assistance on the scene may be one of the explanations for our observations [START_REF] Valeriano | Crowdsourcing to save lives: a scoping review of bystander alert technologies for out-of-hospital cardiac arrest[END_REF]. For these inaccessibility events, it would be interesting to consider other strategies such as drone delivery [START_REF] Boutilier | Optimizing a drone network to deliver automated external defibrillators[END_REF][START_REF] Claesson | Time to delivery of an automated external defibrillator using a drone for simulated out-of-hospital cardiac arrests vs emergency medical services[END_REF].

BLS by first aid providers

Bag-mask ventilation generates aerosols and therefore poses a high risk of contamination for first aid workers [START_REF] Tran | Aerosol generating procedures and risk of transmission of acute respiratory infections to healthcare workers: a systematic review[END_REF]. The use of a high efficiency particulate air (HEPA) filters between mask and bag, as well as two-hand bagmask ventilation techniques to ensure a tight seal have been promoted [START_REF] Edelson | Interim Guidance for Basic and Advanced Life Support in Adults, Children, and Neonates With Suspected or Confirmed COVID-19: From the Emergency Cardiovascular Care Committee and Get With the Guidelines®-Resuscitation Adult and Pediatric Task Forces of the American Heart Association in Collaboration with the American Academy of Pediatrics, American Association for Respiratory Care, American College of Emergency Physicians, The Society of Critical Care Anesthesiologists, and American Society of Anesthesiologists: Supporting Organizations: American Association of Critical Care Nurses and National EMS Physicians[END_REF]. If MMT arrival is rapid, tracheal intubation must be performed, but if not, a simple passive oxygenation with non-rebreathing face mask (NRFM), covered by a surgical mask should be considered [START_REF] Edelson | Interim Guidance for Basic and Advanced Life Support in Adults, Children, and Neonates With Suspected or Confirmed COVID-19: From the Emergency Cardiovascular Care Committee and Get With the Guidelines®-Resuscitation Adult and Pediatric Task Forces of the American Heart Association in Collaboration with the American Academy of Pediatrics, American Association for Respiratory Care, American College of Emergency Physicians, The Society of Critical Care Anesthesiologists, and American Society of Anesthesiologists: Supporting Organizations: American Association of Critical Care Nurses and National EMS Physicians[END_REF]. In our study, we observed less CPR initiation and less defibrillator use (i.e. just the application of the pads without necessarily shocking) by first aid providers during the COVID-19 period. Yet, there is no clear evidence that defibrillation generates aerosols [START_REF] Couper | COVID-19 in cardiac arrest and infection risk to rescuers: a systematic review[END_REF]. Paradoxically, bag-mask ventilation which generates aerosols, was performed just as frequently in both COVID-19 and non-COVID-19 periods.

ALS by Mobile medical team

Despite the COVID-19 outbreak impact on emergency medical systems, the arrival time of MMT was similar between the two periods. This agreed with an OHCA analysis in Paris, France, in March 2020 [START_REF] Lapostolle | Collateral consequences of COVID-19 epidemic in greater Paris[END_REF].

Tracheal intubation is frequently performed by MMT upon arrival at an OHCA [START_REF] Javaudin | Maximum value of end-tidal carbon dioxide concentrations during resuscitation as an indicator of return of spontaneous circulation in out-of-hospital cardiac arrest[END_REF]. The rate of tracheal intubation failure is low (approximately 2%) when an airway is provided by an out-of-hospital emergency physician [START_REF] Jabre | Effect of bag-mask ventilation vs endotracheal intubation during cardiopulmonary resuscitation on neurological outcome after out-of-hospital cardiorespiratory arrest: a randomized clinical trial[END_REF]. In spite of additional hygiene precautions (i.e. donning PPE and limiting personnel), we have not observed additional intubation failures or time delays during the COVID-19 period. Even if no delays were observed in time to intubation or epinephrine injection during the COVID-19 period, when compared to the non-COVID-19 period, we observed that the MMT implemented less injections or tracheal intubations, due to the fact that less ALS were initiated. Similarly, there was little use for intraosseous routes during both periods (approximately 8%). However, it would appear that intraosseous routes may be easier for medical personnel in full protective gear [START_REF] Smereka | Which intravascular access should we use in patients with suspected/confirmed COVID-19?[END_REF]. This injection route is not widely used in France, and is not associated with a poorer prognosis, when compared to conventional peripheral venous routes [START_REF] Baert | Intraosseous Versus Peripheral Intravenous Access During Out-of-Hospital Cardiac Arrest: a Comparison of 30-Day Survival and Neurological Outcome in the French National Registry[END_REF].

Hence, during the COVID-19 period, patients received less resuscitation by MMT (ALS). An explanation for this could be that bystanders and first aid providers initiated less CPR, which lengthened no-flow durations in patients. This situation, no longer compatible with good outcomes, causing the MMT to stop resuscitation.

Outcome

Critically ill patients with SARS-CoV-2 pneumonia have poor survival rates [START_REF] Shao | In-hospital cardiac arrest outcomes among patients with COVID-19 pneumonia in Wuhan, China[END_REF]. When they experience cardiac arrest in hospital, the outcome is even worse. Indeed, D30 survival is approximately 3%, and D30 with a good neurological outcome is less than 1% [START_REF] Shao | In-hospital cardiac arrest outcomes among patients with COVID-19 pneumonia in Wuhan, China[END_REF]. In our series of cases with COVID-19, we observed less survivors 30 days following OHCA although we did not observe differences in BLS or ALS practices between COVID-19 OHCA and non-COVID-19 OHCA. We therefore observed a period effect explaining the differences in CPR. During the COVID-19 period, the rate of ROSC and D30 survival for all medical OHCA was very poor. The most compelling explanation was the decreased onset of resuscitation for both BLS and ALS, and decreased defibrillator use by first aid providers.

Limitations

Our study had several limitations. One was related to the RéAC registry. This registry is based on the voluntary participation of MMT, hence not all MMT participate in the registry. However, those MMT who participated were spread across France, and provided good overviews of French practices.

Another limitation involved the rapid execution of the study and the included data. Hence, the comparison of the number of patients included during the COVID-19 period and non-COVID-19 period should be performed with caution. Indeed, during this outbreak period, it was difficult for some MMT investigators to include patients in the RéAC registry, therefore all participating MMT did not include all their patients. Nevertheless, our aim was not to perform incidence calculations, therefore we included all registered OHCA (during the COVID-19 and non-COVID-19 period). Even if less patients were included in the COVID-19 period in our study, it was just a non-exhaustive cohort of patients, an increase of MMT French activity was observed as well as in Italy [START_REF] Baldi | Out-of-hospital cardiac arrest during the Covid-19 outbreak in Italy[END_REF][START_REF] Marijon | Out-of-hospital cardiac arrest during the COVID-19 pandemic in Paris, France: a population-based, observational study[END_REF]. This may have led to a selection bias, but our aim was to collect as much data as possible. Admittedly, this point limits the generalisability of the data, but does not preclude drawing at least tentative conclusions.

Moreover, the survival rate in this particular period, with all the cofounders associated with the COVID-19 cases should not be generalised. Factors external to the COVID-19 may have had an impact as well.

The final study limitation relates to the issue that some OHCAs may have been misclassified with regard to their COVID-19 status. Indeed, some of the "non-COVID-19" cases may have been false negatives; moreover, we did not have access to post-mortem information. The limited access to COVID-19 testing in France may have led to the under-diagnosis of COVID-19 cases.

Conclusions

To conclude, during the COVID-19 period, we observed decreased initiation of CPR by bystanders and first aid providers for BLS, and decreased ALS by the MMT, regardless if subjects were infected with SARS-CoV-2 or not. ROSC rates and survival were also greatly reduced, even for non-COVID-19 subjects. It is now urgent and essential to communicate good resuscitation practices during this COVID-19 period, to avoid drastic and lasting reductions in survival rates after an OHCA.

Fig. 1

 1 Fig. 1 Study flow chart. DNAR: Do Not Attempt Resuscitation, RéAC, French national out-of-hospital Cardiac Arrest Registry

Table 1

 1 Patient characteristics

		All patients	COVID-19 period	Non-COVID-19 period	p-value
		N = 2625	N = 1005	N = 1620
	Age, mean ± SD, y	68 ± 17	68 ± 17	69 ± 17	0.137
	Sex (Male), No./total (%)	1747/2625 (66.6)	676/1005 (67.3)	1071/1620 (66.1)	0.552
	Medical history, No./total (%)
	-Diabetes	395/2625 (15.0)	156/1005 (15.5)	239/1620 (14.8)	0.613
	-Cardiovascular	1249/2625 (47.6)	478/1005 (47.6)	771/1620 (47.6)	1.000
	-Respiratory	409/2625 (15.6)	160/1005 (15.9)	249/1620 (15.2)	0.740
	-Other	746/2625 (28.4)	262/1005 (26.1)	484/1620 (29.9)	0.036
	-None	155/2625 (5.9)	46/1005 (4.6)	109/1620 (6.7)	0.026
	OHCA location (home), No./total (%)	1975/2483 (75.5)	819/971 (84.4)	1156/1512 (76.5)	< 0.001
	OHCA cause, No./total (%)				0.002
	-Cardiac	2001/2625 (76.2)	726/1005 (72.2)	1275/1620 (78.7)
	-Respiratory	470/2625 (17.9)	210/1005 (20.9)	260/1620 (16.0)
	-Neurological	44/2625 (1.7)	19/1005 (1.9)	25/1620 (1.5)
	-Other medical cause	110/2625 (4.2)	50/1005 (5.0)	60/1620 (3.7)
	Survival ROSC, No./total (%)	604/2615 (23.1)	195/999 (19.5)	409/1616 (25.3)	0.001
	D30 Survival, No./total (%)	125/2483 (5.1)	26/937 (2.8)	99/1546 (6.4)	0.001

Table 2

 2 BLS characteristics frequently in the COVID-19 period group (84.3% vs. 88.7%; difference, -4.4 percentage points [95% CI, -7.1 to -1.6]), and the defibrillator was less frequently used (66.0% vs. 74.1%; difference, -8.2 percentage points [95% CI, -11.8 to -4.6]

	All patients	COVID-19 period	Non-COVID-19 period	p-value
	N = 2625	N = 1005	N = 1620

Data are expressed as the number/total number (frequency %) for qualitative variables or mean ± standard deviation for quantitative variables MMT mobile medical team, BLS basic life support, CC chest compressions, MtM mouth to mouth, CPR cardiopulmonary resuscitation, AED automated external defibrillator a Time between collapse and CPR initiation attempted less

Table 3

 3 19 period (67.3% vs. 75.0%; difference, -7.7 percentage points [95% CI, -11.3 to -4.1]), and adrenaline was less frequently injected (61.8% vs. 67.9%; difference, -6.2 percentage points [95% CI, -10.0 to -2.4]). The absence of injection routes implementation was more frequent during the COVID-19 period (34.2% vs. 26.8%; difference, 7.4 percentage points [95% CI, 3.8 to 11.1]). Tracheal intubation was less implemented (61.6% vs. 69.1%; difference, -7.5 percentage points [95% CI, -11.2 to -3.7]). ALS characteristics

			COVID-19 and OHCA victims
			Focusing on the COVID-19 period (between March 1st
			and April 31st 2020), when we compared COVID-19
			victims of OHCA and non-COVID-19 patients (Table 4),
			no differences were observed for age, location of OHCA,
			bystander BLS, first aid provider of BLS and ALS imple-
			mentation. However, COVID-19 patients were less likely
			to be male (59.4% vs. 69.2%; difference, -9.7 percentage
			points [95% CI, -17.3 to -2.2]), present more respira-
			tory histories (23.4% vs. 14.1%; difference, 9.2 percentage
			points [95% CI, 2.9 to 15.6]), and had a more respiratory
			aetiology of OHCA (56.9% vs. 12.1%; difference, 44.7
			percentage points [95% CI, 37.5 to 52.0]). In the
			COVID-19 OHCA group, no flow duration (time be-
			tween OHCA and the first resuscitation) was longer
			(18 ± 22 min vs. 14 ± 17 min; mean difference, 4.0 [95%
			CI, 1.2 to 6.8]), and the time between T0 and ROSC or
			death was also longer (48 ± 27 min vs. 43 ± 23 min; mean
		All patients	COVID-19 period	Non-COVID-19 period	p-value
		N = 2625	N = 1005	N = 1620
	Times, mean ± SD, min
	Time between T0 and MMT arrival	22 ± 15	23 ± 18	22 ± 13	0.461
	Time between T0 and intubation	28 ± 13	28 ± 13	28 ± 13	0.568
	Time between T0 and epinephrine	26 ± 12	27 ± 13	26 ± 13	0.400
	Time between T0 and ROSC or death	42 ± 22	44 ± 24	42 ± 21	0.342
	Resuscitation practices
	First recorded cardiac rhythm, No./total (%)				0.226

COVID-19 patients (0.0% vs. 3.5%; difference, -3.5 percentage points [95% CI, -5.1 to -1.2]). Respiratory causes were more frequent during this COVID-19 period (20.9% vs. 16.0%; difference, 4.8 percentage points [95% CI, 1.8 to 7.9]).

Table 4

 4 Comparisons between COVID-19 and non-COVID-19 patients during the COVID-19 period only (between March 1st and April 31st 2020)Time between collapse and initiation of CPR Data are expressed as the number/total number (frequency %) for qualitative variables or mean ± standard deviation for quantitative variables OHCA out-of-hospital cardiac arrest, MMT mobile medical team, ROSC return of spontaneous circulation, VF/pulseless VT ventricular fibrillation/pulseless tachycardia, PEA pulseless electrical activity, BLS basic life support, ALS advanced life support, PIV peripheral intravenous access, IO intraosseous COVID-19 period, highlighting the potential impact of SARS-CoV-2 on CPR outcomes.

	COVID-19 patients	Non-COVID-19 patients	p-value
	N = 197	N = 808

a If a bystander is present, % of BLS initiated immediately at the collapse time b

Data are expressed as the number/total number (frequency %) for qualitative variables or mean ± standard deviation for quantitative variables MMT mobile medical team, ROSC return of spontaneous circulation, VF/pulseless VT ventricular fibrillation/pulseless tachycardia, PEA pulseless electrical activity, BLS basic life support, ALS advanced life support, PIV peripheral intravenous access, IO intraosseous, AED automated external defibrillator

Acknowledgments

We thank especially for the inclusion of patients during the COVID period: Delphine Hugenschmitt, Thomas Bony, Clément Babin, Rudy Cohen, Natacha Ngoyi, Sébastien Jonquet, Terence Ahui, Tom Handwerk, Patrice Serre, Nadia Mansouri, François Revaux, Adèle Barbery, Mariane Ovtcharenko, Cécile Ursat,

Funding

The RéAC registry is supported by the French Society of Emergency Medicine (SFMU), a patient foundation -Fédération Française de Cardiologie, the Mutuelle Générale de l'Education Nationale (MGEN), the University of Lille and the Institute of Health Engineering of Lille.

Availability of data and materials

Data are available on request to the corresponding author.

FJ, VB, HH and TC conceived and designed the study and drafted the manuscript. VB, FJ and HH computed statistics. DJ, JBL and GD brought critical revision to the manuscript for important intellectual content. All authors review and revised the manuscript and approves the final version.

Ethics approval and consent to participate

This study was approved as a medical registry assessment by the French Advisory Committee on Information Processing in Health Research (CCTIRS), and by the French National Data Protection Commission (CNIL, authorisation number; 910946). This study was approved as a medical registry assessment without the requirement for patient consent.

Consent for publication

Not applicable.

Competing interests

The authors declare that they have no competing interests.

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