CARES indicates Cardiac Arrest Registry to Enhance Survival; DNR, do not resuscitate; and NC, North Carolina.
Shown are trends in survival to discharge (A) and favorable neurological survival at discharge (B) stratified for both home and public locations for out-of-hospital cardiac arrest.
A and B, Shown is the adjusted mortality among patients who received out-of-hospital cardiopulmonary resuscitation and defibrillation at home (A) and in public (B). C and D, Shown is the adjusted survival to discharge with good neurological function (cerebral performance category 1 or 2) among patients who received out-of-hospital cardiopulmonary resuscitation and defibrillation at home (C) and in public (D). The combination of bystander cardiopulmonary resuscitation and either first-responder defibrillation (at home) or bystander defibrillation (in public) was most strongly associated with both age and sex–adjusted survival and age and sex–adjusted favorable neurological survival (reference EMS/EMS). EMS indicates emergency medical services; NA, not applicable; and OR, odds ratio.
aNote that we could not calculate the OR for bystander/bystander efforts in A and C.
eTable. Postresuscitation Management for Home and Public Out-of-Hospital Cardiac Arrest
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Fordyce CB, Hansen CM, Kragholm K, et al. Association of Public Health Initiatives With Outcomes for Out-of-Hospital Cardiac Arrest at Home and in Public Locations. JAMA Cardiol. 2017;2(11):1226–1235. doi:10.1001/jamacardio.2017.3471
Do comprehensive public health initiatives improve prehospital resuscitation efforts and outcomes for patients with out-of-hospital cardiac arrest at home, where outcomes are especially poor, and in public locations?
Among 8269 patients, this study demonstrates that resuscitation efforts and outcomes in those with out-of-hospital cardiac arrest at home and in public may be improved through coordinated, multifaceted public health initiatives targeting multiple personnel across the cardiac arrest “chain of survival,” including first-responder programs.
Adopting some of these public health initiatives may be helpful for communities aiming to improve outcomes of out-of-hospital cardiac arrest, including at home.
Little is known about the influence of comprehensive public health initiatives according to out-of-hospital cardiac arrest (OHCA) location, particularly at home, where resuscitation efforts and outcomes have historically been poor.
To describe temporal trends in bystander cardiopulmonary resuscitation (CPR) and first-responder defibrillation for OHCAs stratified by home vs public location and their association with survival and neurological outcomes.
Design, Setting, and Participants
This observational study reviewed 8269 patients with OHCAs (5602 [67.7%] at home and 2667 [32.3%] in public) for whom resuscitation was attempted using data from the Cardiac Arrest Registry to Enhance Survival (CARES) from January 1, 2010, through December 31, 2014. The setting was 16 counties in North Carolina.
Patients were stratified by home vs public OHCA. Public health initiatives to improve bystander and first-responder interventions included training members of the general population in CPR and in the use of automated external defibrillators, teaching first responders about team-based CPR (eg, automated external defibrillator use and high-performance CPR), and instructing dispatch centers on recognition of cardiac arrest.
Main Outcomes and Measures
Association of resuscitation efforts with survival and neurological outcomes from 2010 through 2014.
Among home OHCA patients (n = 5602), the median age was 64 years, and 62.2% were male; among public OHCA patients (n = 2667), the median age was 68 years, and 61.5% were male. After comprehensive public health initiatives, the proportion of patients receiving bystander CPR increased at home (from 28.3% [275 of 973] to 41.3% [498 of 1206], P < .001) and in public (from 61.0% [275 of 451] to 70.5% [424 of 601], P = .01), while first-responder defibrillation increased at home (from 42.2% [132 of 313] to 50.8% [212 of 417], P = .02) but not significantly in public (from 33.1% [58 of 175] to 37.8% [93 of 246], P = .17). Survival to discharge improved for arrests at home (from 5.7% [60 of 1057] to 8.1% [100 of 1238], P = .047) and in public (from 10.8% [50 of 464] to 16.2% [98 of 604], P = .04). Compared with emergency medical services–initiated CPR and resuscitation, patients with home OHCA were significantly more likely to survive to hospital discharge if they received bystander-initiated CPR and first-responder defibrillation (odds ratio, 1.55; 95% CI, 1.01-2.38). Patients with arrests in public were most likely to survive if they received both bystander-initiated CPR and defibrillation (odds ratio, 4.33; 95% CI, 2.11-8.87).
Conclusions and Relevance
After coordinated and comprehensive public health initiatives, more patients received bystander CPR and first-responder defibrillation at home and in public, which was associated with improved survival.
Almost 400 000 Americans experience out-of-hospital cardiac arrest (OHCA) annually,1 but less than 10% of them survive to hospital discharge. Although up to 80% of all OHCAs occur at home, those who experience an at-home OHCA have a 4 to 5 times lower chance of survival vs those who experience an OHCA in public locations.2-6 Poorer outcomes may be related to differences in patient characteristics (eg, greater comorbidities), longer delay of cardiopulmonary resuscitation (CPR) initiation and emergency medical services (EMS) arrival, higher probability of an unwitnessed arrest, and lower frequency of shockable initial rhythms.2-4,7 In 2015, the Institute of Medicine,8 supported by the American Heart Association,9 called for more research focusing on the location of cardiac arrest in recognition of the knowledge gaps and poor outcomes for at-home OHCA.
Little is known about the influence of public health initiatives, including widespread training of laypersons in CPR and first responders in high-performance CPR and automated external defibrillator (AED) use, to improve bystander and first-responder resuscitation efforts in patients who experience at-home cardiac arrest. In fact, there are concerns that expanded CPR training may not correct the large fraction of cardiac arrests that occur at home.10 Studies11-15 have demonstrated that community education and quality improvement programs to increase bystander and first-responder intervention, including CPR and defibrillation, and access to AEDs are associated with improved outcomes, including survival. However, a recent Danish study16 found that public health initiatives increased bystander AED use in public but not in residential areas. The North Carolina Regional Approach to Cardiovascular Emergencies Cardiac Arrest Resuscitation System (RACE CARS) program initiated multicomponent interventions to improve OHCA care in 2010; it improved care processes and led to a greater likelihood of survival.12 Interventions included community training in chest compression–only CPR, providing emergency medical dispatcher training on early recognition of cardiac arrest and instructing bystanders to provide CPR, first-responder training in team-based CPR, and several in-hospital interventions, among others.
We aimed to describe temporal trends in bystander CPR and first-responder defibrillation stratified by OHCA location at home (private home or residence) or in public. Their associations with survival and neurological outcomes in North Carolina between January 1, 2010, and December 31, 2014, were investigated.
The Cardiac Arrest Registry to Enhance Survival (CARES)17 is a voluntary, prospective clinical registry of patients with OHCA in the United States. All patients with a confirmed nontraumatic OHCA (defined as apneic and unresponsive) for whom resuscitation by bystanders, first responders, or EMS personnel is attempted are included in the registry. Furthermore, those with termination of resuscitation before hospital arrival are included. Standardized international Utstein18 definitions for clinical variables and outcomes are used to encourage reporting uniformity. In North Carolina, a team of data consultants (including C.T.) assisted with training, quality control, and data feedback to county EMS agencies to ensure that the collected CARES data were of high quality. The Duke University Medical Center Institutional Review Board approved this study research as minimal risk.
To reduce the chance that our results were driven by changes in reporting, we included only North Carolina counties with complete registry enrollment from 2010 through 2014. Therefore, the study population included all nontraumatic OHCAs from 16 counties in North Carolina (Alexander, Alleghany, Brunswick, Camden, Catawba, Durham, Forsyth, Mecklenburg, Pasquotank, Stanly, Stokes, Surry, Transylvania, Wake, Warren, and Yadkin), comprising a total population of approximately 3.3 million inhabitants in 2014 (one-third of the state’s total population),19 with demographics varying from urban to rural areas, served by 16 EMS agencies.12,20 The remaining 54 counties reporting data to CARES did not have complete countywide registry enrollment for the study years and were excluded from this analysis because temporal trends could not be accurately calculated. We included arrests of presumed cardiac cause and excluded cases witnessed by EMS or with do-not-resuscitate orders, following Utstein18 guidelines. Our study population of 8269 patients (see the Study Population subsection of the Results section for the cohort derivation) included 4291 individuals from a prior analysis12 describing trends in prehospital interventions and outcomes from 2010 through 2013 with the addition of 5 counties and a subsequent calendar year (2014). An arrest was presumed to be of cardiac etiology unless it was known or likely to have been caused by trauma, drowning, respiratory causes, electrocution, drug overdose, presumed poisoning or intoxication, asphyxia, exsanguinations, or any other noncardiac cause as best determined by rescuers. All included EMS agencies had 2-tiered response systems, with first responders equipped with AEDs.21 Per CARES, first responders were defined as personnel who responded to the medical emergency in an official capacity as part of an organized medical response team but who were not the designated transporter of the patient to the hospital. First responders included AED-equipped police officers, firefighters, rescue squads, or life-saving crew members trained to perform basic life support until the EMS team arrived and who were called to the scene by emergency medical dispatch centers. Bystanders were defined as persons who were present and had intervened but had not been dispatched, following Utstein18 guidelines. Of 16 EMS agencies, 13 had implemented protocols for dispatch-assisted CPR instruction before the study period, while 3 agencies never implemented these protocols during the study period. Protocols for team-based CPR22 had been implemented by 4 EMS agencies before January 2010 and by 9 EMS agencies during the study period.
In 2010, the HeartRescue Project23 in North Carolina initiated a multifaceted, statewide quality improvement program. The project included intervention for community members, EMS personnel, first responders, and hospital administrators and staff. For community members, chest compression–only training was offered at major civic events and to patients with cardiovascular disease and their family members before hospital discharge. School staff were trained to use AEDs, and community grants were provided to groups to implement CPR training programs. Emergency medical dispatchers were trained to recognize when bystanders described a cardiac arrest and give instructions to provide CPR. First responders were instructed in team-based CPR, including AED use and high-performance CPR. Hospital administrators were encouraged to establish protocols for primary percutaneous coronary intervention (PCI) for ST-segment elevation myocardial infarction, targeted temperature and hypothermia management, and goal-directed intensive unit care, including designated physician leadership to operationalize post–cardiac arrest protocols, with a focus on frequent neurological assessment for prognosis. The full RACE CARS protocol is available online (http://racecars.dcri.org/wp-content/uploads/2014/08/RACE-ops-3.0.pdf).
At-home OHCAs were defined a priori as those occurring in private homes or residences. All other OHCAs were considered public, including those occurring in nursing homes or health care facilities (which we considered to be public due to the greater likelihood of OHCAs being witnessed, including by health care professionals, and because AEDs are more likely to be found in such institutions). Main outcome variables, also defined a priori, were resuscitative efforts through CPR, defibrillation, or both from bystanders and first responders (including the combination of efforts between bystanders and first responders) and patient survival to discharge and favorable neurological survival (measured by cerebral performance category [CPC] 1 or 2).24 A CPC of 1 represents full recovery or mild disability, while a CPC of 2 represents moderate disability but independence in activities of daily living.
Proportions were calculated for categorical data, and the medians (interquartile ranges) were calculated for continuous data. Statistical significance for differences in categorical data was assessed using the Fisher exact test or the χ2 test. Temporal trends for categorical data were assessed using the Cochran-Armitage test for trend across ordered groups (by year) if the Fisher exact test or χ2 test result was statistically significant. Analyses regarding the combination of efforts from bystanders, first responders, and EMS (CPR and defibrillation) included only patients who were defibrillated before hospital arrival. Odds ratios (ORs) with 95% CIs were calculated by logistic regression analyses to examine the association between bystander and first-responder intervention and survival to discharge and favorable neurological survival for the entire study period. Estimates are presented as unadjusted and adjusted (for age and sex). We tested for interaction of location and time for temporal outcomes as well as for location (home vs public) for each combination of effort. A 2-sided P < .05 was considered statistically significant. Age and sex–adjusted results should be interpreted in the context of a lack of adjustment for multiple comparisons and thus are exploratory rather than confirmatory. All analyses were performed using SAS software (version 9.4; SAS Institute Inc), Stata (version 13.0; StataCorp LLC), and GraphPad Prism (version 7; GraphPad Software Inc).
Our study population included 8269 patients with OHCA from counties with complete countywide registry enrollment after excluding patients with noncardiac causes of arrest (n = 1431), predetermined do-not-resuscitate orders (n = 79), or cardiac arrest after EMS arrival (n = 1260) (Figure 1). Patients were then grouped based on OHCA location at home (5602 [67.7%]) vs in public (2667 [32.3%]). Clinical characteristics for OHCAs by location are listed in Table 1. Among home OHCA patients (n = 5602), the median age was 64 years, and 62.2% were male; among public OHCA patients (n = 2667), the median age was 68 years, and 61.5% were male. In general, few temporal changes in the population were observed over the study period at home and in public.
From 2010 through 2014, rates of bystander-initiated CPR significantly increased at home (from 28.3% to 41.3%, P < .01) and in public (from 61.0% to 70.5%, P = .01) (Table 2), which was associated with a concomitant decrease in CPR initiated by first responders and EMS at home and in public locations. During the same period, rates of defibrillation by first responders significantly increased at home (from 42.2% to 50.8%, P = .02) but not in public (from 33.1% to 37.8%, P = .17). There were no significant differences in bystander and EMS defibrillation over the same period. The combined effort of bystander CPR and first-responder defibrillation significantly increased at home (from 14.2% to 23.4%, P = .02), with no significant difference among patients with public OHCA (from 13.8% to 22.9%, P = .08). No significant difference was observed for increased bystander CPR and EMS defibrillation at home (from 17.8% to 21.7%, P = .06), which was significant in public (from 23.0% to 27.3%, P = .049). The rate of combined bystander CPR and bystander defibrillation declined significantly over time at home (from 1.0% to 0.2%, P = .02), although the absolute number of patients was small (n = 6). There was no significant difference in the rate of combined bystander CPR and bystander defibrillation in public (from 20.7% to 19.6%, P = .10). Cardiopulmonary resuscitation initiated by either first responders or EMS generally declined over time as bystander CPR increased.
Over the study period, significantly fewer patients were not declared dead in the field (from 61.3% to 50.2%, P < .01 at home and from 69.4% to 63.0%, P = .03 in public), while more patients were admitted to a hospital ward (from 18.5% to 26.1%, P < .01 at home and from 22.8% to 32.2%, P < .01 in public) (eTable in the Supplement). The proportion of patients with at-home OHCA who were transported to a PCI center significantly increased (from 68.6% to 78.2%, P < .01), as did the proportion receiving targeted temperature management (from 60.1% to 61.5%, P = .04 for trend), which was not seen with public OHCA for either PCI center transport (from 79.5% to 85.4%, P = .21) or targeted temperature management (from 46.6% to 53.1%, P = .05).
From 2010 through 2014, survival to hospital discharge significantly increased both at home (from 5.7% [60 of 1057] to 8.1% [100 of 1238], P = .047) and in public locations (from 10.8% [50 of 464] to 16.2% [98 of 604], P = .04) (Figure 2). Favorable neurological survival (CPC 1 or 2) significantly increased in public (from 9.5% [44 of 464] to 14.7% [89 of 604], P = .02) but not among patients with at-home OHCA (from 4.9% [52 of 1057] to 6.1% [76 of 1238], P = .06). We found a significant interaction for both survival and favorable neurological survival by location (P < .05 for interaction) but not between location and time.
After adjustment for age and sex, patients with at-home OHCA who received bystander-initiated CPR and first-responder defibrillation were the most likely to survive to hospital discharge vs patients receiving other combinations of CPR and defibrillation (OR, 1.55; 95% CI, 1.01-2.38 [reference EMS CPR and defibrillation]) (Figure 3A). Patients with public OHCA were most likely to survive to discharge if they received both bystander-initiated CPR and bystander defibrillation (OR, 4.33; 95% CI, 2.11-8.87) (Figure 3B). A similar directionality favoring survival was observed for patients with at-home OHCA, who were more likely to survive to discharge with good neurological function (CPC 1 or 2) if they received bystander CPR and first-responder defibrillation, although this result was nonsignificant (OR, 1.54; 95% CI, 0.98-2.43) (Figure 3C). Those with public OHCA were significantly more likely to survive with good neurological outcome if they received both bystander-initiated CPR and defibrillation (OR, 4.46; 95% CI, 2.11-9.40) (Figure 3D). We found significant interactions (P < .05) between locations for some combinations of resuscitation efforts for both survival (combined bystander CPR and first-responder defibrillation and combined bystander CPR and EMS defibrillation) and favorable neurological survival (combined bystander CPR and first-responder defibrillation).
After coordinated and comprehensive public health initiatives, more patients received bystander CPR and first-responder defibrillation at home and in public. This uptake of key care processes was associated with improved survival at home and in public, as well favorable neurological survival among patients with public OHCA.
Although most OHCAs occur at home, historical outcomes have been significantly worse compared with public OHCAs.2-6 This finding has increased urgency to identify strategies for improving survival among these particularly vulnerable patients.9,12 Our data indicate that coordinated, multifaceted public health initiatives targeting multiple personnel across the cardiac arrest “chain of survival,” including first-responder programs, are associated with improved outcomes among individuals with at-home OHCA.25 This result occurs despite concerns that such initiatives were not previously associated with improved survival for at-home OHCA.10 A 2013 Danish study26 showed that coordinated efforts over many years led to improved outcomes for OHCA. A national CPR training program in Sweden11 improved CPR nationwide and was associated with a significant overall increase in bystander CPR and OHCA survival. However, only 29% of patients experiencing a witnessed cardiac arrest at home received bystander CPR compared with 50% in public. A more recent Swedish study,27 with approximately 70% of patients experiencing at-home OHCA, found that a mobile phone positioning system to dispatch lay volunteers trained in CPR was associated with significantly increased rates of bystander-initiated CPR among persons with OHCA. In contrast, the RACE CARS program involved more comprehensive bystander and first-responder interventions, including AED training.
We also extend prior findings to a mixed rural and urban population in the United States with multiple EMS agencies and demonstrate that the combination of bystander CPR and first-responder defibrillation at home is significantly associated with improved favorable neurological survival. Our results are congruent with a recent Swedish study,28 which found that CPR performed before EMS arrival was associated with improved 30-day survival rates after OHCA. Finally, the role of early first-responder defibrillation for at-home OHCA may be particularly important because AEDs are not typically available in private residences.20
There are several possible explanations why at-home OHCA carries a poorer prognosis than public OHCA. First, bystander-initiated CPR before EMS arrival is less frequent in this setting,8,29 as was the case in our study. At-home OHCA is more frequently unwitnessed or witnessed by elderly persons who may not be trained in CPR or are incapable of performing it effectively.30,31 While we found that bystander CPR rates were lower at home (and associated with lower survival comapred to public OHCA), this finding cannot be explained by age alone because those with at-home OHCA were younger than their public counterparts (median age, 64 vs 68 years). This result may occur in part because we only considered private homes (and not nursing homes) in our definition of home. Bystanders at home are frequently family members or close associates, potentially with emotional barriers that could hinder resuscitation efforts, including concern about causing harm,32 panic,33 or fear of failure.34 Second, the incidence of shockable rhythms (pulseless ventricular tachycardia or ventricular fibrillation) has been historically lower in the home setting.29 We found that a shockable rhythm occurred in 21.0% (1174 of 5599) and 26.5% (706 of 2665) of at-home and public OHCAs, respectively, which is consistent with this fact. This finding is plausibly related to delayed EMS contact or arrival, thereby increasing the likelihood that a shockable rhythm will degenerate to asystole,35 or may be associated with other factors, such as concomitant comorbidities.2 Third, it is also possible that being in public (vs at home) is a marker for better overall health.
Therefore, improvements in survival after public health initiatives for at-home OHCA are multifactorial and may be explained by improvements in each link in the chain of survival,25 including first-responder programs that decrease time to defibrillation while the bystander has initiated CPR.20 Recent initiatives in Denmark resulted in a marked uptake of public but not residential defibrillation.16 This result reinforces the importance of AEDs being transported by dispatched professional first responders, which is associated with improved survival in residential areas, where AEDs are often unavailable. Communities seeking to improve survival in residential areas should consider implementing and measuring the influence of dispatched first responders who can provide defibrillation before EMS arrival.
Our study has some limitations. First, this investigation was an observational study for which unmeasured or unmeasurable confounders (or secular trends) could explain improved temporal outcomes independent of public health initiatives. Second, our results only apply to the counties studied. However, these counties were selected based on complete countywide registry enrollment and high accuracy of data, including low rates of missingness, which are critical statistical considerations when describing trends. Third, these results are mostly applicable to mixed rural and urban populations who employ first responders as part of prehospital response to OHCA. However, the finding that first-responder defibrillation (before EMS arrival) is associated with improved outcomes in the home setting emphasizes the need for early defibrillation and thus is generalizable for regions without first responders. Fourth, our data set did not include long-term outcomes after hospital discharge. However, recent evidence suggests that patients who are discharged alive after OHCA have good prognoses, which supports these prehospital efforts.36,37 Fifth, our definition of at-home OHCA included only private homes or residences. As such, patient characteristics and outcomes may differ compared with studies that used a broader definition, including residential institutions (nursing homes) or other nonpublic locations.29 However, we were strict with our definition because we aimed to determine whether public health interventions were associated with improvements in home locations without routine access to professionals trained in CPR, AEDs, or other forms of defibrillation. Sixth, despite the fact that public health initiatives improved outcomes over a 5-year period, many patients still did not receive early CPR or defibrillation, and survival was low. This finding highlights future opportunities to improve overall survival rates, including for at-home OHCA.
In summary, we found that after public health initiatives, more patients received bystander CPR and first-responder defibrillation, which was associated with increased rates of survival at home and in public. Specifically, initiatives to improve bystander CPR and early defibrillation are associated with better outcomes for OHCAs at home, where the prognosis has traditionally been poor. Adopting some of these public health initiatives may likely be helpful for communities aiming to improve outcomes of OHCA.
Accepted for Publication: August 8, 2017.
Corresponding Author: Christopher B. Fordyce, MD, MHS, MSc, Division of Cardiology, Department of Medicine, University of British Columbia, 2775 Laurel St, Ninth Floor, Vancouver, BC V5Z 1M9, Canada (firstname.lastname@example.org).
Published Online: October 4, 2017. doi:10.1001/jamacardio.2017.3471
Author Contributions: Drs Fordyce and Dupre had full access to all of the data in the study and take responsibility for the integrity of the data and the accuracy of the data analysis.
Study concept and design: Fordyce, C. M. Hansen, Becker, Corbett, Pearson, van Diepen, Granger.
Acquisition, analysis, or interpretation of data: Fordyce, C. M. Hansen, Kragholm, Dupre, Jollis, Roettig, Becker, S. M. Hansen, Hinohara, Corbett, Monk, Nelson, Pearson, Tyson, van Diepen, Anderson, McNally.
Drafting of the manuscript: Fordyce, C. M. Hansen, Hinohara, Nelson, Pearson.
Critical revision of the manuscript for important intellectual content: All authors.
Statistical analysis: Fordyce, Kragholm, Dupre.
Obtained funding: Jollis, Roettig.
Administrative, technical, or material support: Roettig, Becker, Corbett, Monk, Nelson, Pearson, Tyson, van Diepen, Anderson.
Study supervision: C. M. Hansen, Kragholm, Pearson, Granger.
Conflict of Interest Disclosures: All authors have completed and submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest. Dr Fordyce reported serving on an advisory board for Bayer. Dr C. M. Hansen reported receiving research grants from the Laerdal Foundation, TrygFonden, and Helsefonden. Dr Kragholm reported receiving a research grant from the Laerdal Foundation and speaker’s honoraria from Novartis. Dr Jollis reported receiving grants from the Medtronic Foundation. Dr Becker reported receiving institutional grants or research support (funds go to Northwell Health) from Philips Medical Systems, National Institutes of Health (NIH), ZOLL Medical Corporation, and Nihon Kohden; reported serving as a scientific consultant or on advisory panels for the NIH Data Safety Monitoring Board and Protocol Review Committee, NIH Resuscitation Outcomes Consortium, and NIH New York Icahn School of Medicine at Mount Sinai K12 Training Grant; reported serving on a scientific advisory board for Nihon Kohden; reported holding patents for hypothermia induction and reperfusion therapies, including 7 issued patents and several pending patents involving the use of medical slurries as human coolant devices to create slurries, as well as reperfusion cocktails; reported owning equity and royalties in privately held companies, including inventor’s equity and royalties from Helar, a company started by the University of Pennsylvania to develop technologies for medical cooling using slurry technology; and reported long-standing volunteer membership in the American Heart Association (currently serving on several committees), which has a financial interest in the outcome of resuscitation studies being conducted. Dr S. M. Hansen reported receiving grants from the Laerdal Foundation. Dr Granger reported receiving grants from the Medtronic Foundation. No other disclosures were reported.
Funding/Support: This study was supported by the HeartRescue Project, which is funded by the Medtronic Foundation.
Role of the Funder/Sponsor: The study sponsors had no role in the design and conduct of the study; the collection, management, analysis, or interpretation of the data; the preparation, review, or approval of the manuscript; or the decision to submit the manuscript for publication.
Additional Contributions: Morgan deBlecourt, BA, provided editorial assistance for the manuscript as part of her regular duties as medical editor employed by the Duke Clinical Research Institute. We acknowledge the efforts of the emergency medical services and hospital personnel who completed the case report forms for the Cardiac Arrest Registry to Enhance Survival (CARES).
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