a b s t r a c t

Introduction: Out-of-hospital cardiac arrests contribute to significant morbidity and mortality in both non- military/civilian and military populations. Early CPR and AED use have been linked with improved outcomes. There is public health interest in Identifying communities with high rates of both with the hopes of creating gen- eralizable tactics for improving cardiac arrest survival.

Methods: We examined a national registry of EMS activations in the United States (NEMSIS). Inclusion criteria were witnessed cardiac arrests from January 2020 to September 2022 where EMS providers documented the location of the arrest, whether CPR was provided prior to their arrival (yes/no), and whether an AED was applied prior to their arrival (yes/no). Cardiac arrests were then classified as occurring on a military base or in a non-military setting.

Results: A total of 60 witnessed cardiac arrests on military bases and 202,605 witnessed cardiac arrests in non- military settings met inclusion criteria. Importantly, the prevalence of CPR and AED use prior to EMS arrival was sig- nificantly higher on military bases compared to non-military settings.

Conclusions: Reasons for the trends we observed may be a greater availability of CPR-trained individuals and AEDs on

military bases, as well as a widespread willingness to provide aid to victims of cardiac arrest. Further research should examine cardiac arrests on military bases.

(C) 2022

1. Background

Globally, out-of-hospital cardiac arrest remains a significant Public health concern, and there is ample room for improvements in survival [1-3]. It has been well-established in the literature that early CPR and defibrillation significantly improve a given cardiac arrest victim’s chance of a favorable outcome [4]. These important ideas have been enshrined as links in the cardiac arrest “Chain of survival” [5]. Several studies have shown that communities with stronger chains of Survival benefit from significantly-improved cardiac arrest survival [6,7]. By con- trast, other studies have reported community-level disparities in early resuscitation and cardiac arrest survival on the basis of demographics and neighborhood socioeconomic status [8-14].

* Corresponding author at: The Icahn School of Medicine at Mount Sinai, New York City, NY, United States of America.

E-mail address: [email protected] (A.C. Shekhar).

Given community-level disparities in early resuscitation and cardiac arrest survival, we hypothesize there may be communities with highly-favorable Cardiac arrest outcomes [13,14]. These might include communities with an abundance of CPR-trained individuals and easily- accessible automated external defibrillators (AEDs) that can be quickly applied on cardiac arrest patients. Military bases may be a unique setting to study cardiac arrest, given they likely have a significantly greater con- centration of AEDs and CPR-trained individuals than non-military settings [15-20]. In this study, we examined a cohort of witnessed cardiac arrests that took place on military bases and compared them with a cohort of cardiac arrests that took place in non-military settings.

1. Methods

The National Emergency Medical Services Information System (NEMSIS) is a database of millions of EMS activations in the United States [21,22]. NEMSIS data is gathered directly from EMS patient care

https://doi.org/10.1016/j.ajem.2022.12.014

0735-6757/(C) 2022

reports, and estimates suggest the database contains a majority of EMS runs within the United States [23] Given EMS’ central role in responding to out-of-hospital cardiac arrests, data from the EMS perspective can be invaluable when analyzing trends in the incidence and initial treatment of cardiac arrest [5]. We queried the NEMSIS database for witnessed car- diac arrests occurring between January 1, 2020 and September 30, 2022. Cardiac arrests were included for analysis if EMS documented all of the following: the location of the cardiac arrest, whether CPR had been started prior to ambulance arrival, and whether an AED had been applied prior to ambulance arrival. Interventions prior to ambulance arrival may have been performed by bystanders or other First responders. Using the EMS-documented location of the arrest, we clas- sified arrests as occurring either on military bases or in non-military (civilian) settings. Cardiac arrests with incomplete data were excluded from the analysis. One-tailed two-proportion z-tests were used to establish statistical significance; significance was defined as p < 0.05.

1. Results

A total of 60 witnessed cardiac arrests on military bases and 202,665 witnessed cardiac arrests in non-military settings met inclusion criteria (Table 1). Several key differences between these cohorts are worth discussing. First, rates of pre-EMS CPR and pre-EMS AED use were signifi- cantly higher on military bases when compared with non-military settings (p < 0.001). Second, rates of shockable first monitored arrest rhythms were significantly higher on military bases than non-military settings (p < 0.001). Third, cardiac arrest victims on military bases were signifi- cantly younger than cardiac arrest victims in non-military settings.

1. Discussion

The main finding from our study is that military bases are associated with significantly-higher rates of early resuscitation for witnessed ar- rests when compared with non-military settings. Specifically, we report higher rates of CPR care and AED use prior to EMS arrival. As discussed earlier, early CPR is crucial to improving cardiac arrest outcomes by cir- culating blood in order to prevent irreversible injury to metabolically- demanding organs [4,5]. Our findings likely reflect greater CPR training within the military when compared with the civilian population. This finding is unsurprising given that CPR training is a routine component of US military training [18,20]. Increased rates of early CPR may partially explain why a significantly greater proportion of cardiac arrests on mil- itary bases presented as shockable to EMS. Early CPR has also been

Table 1

Cardiac arrests on military bases vs. non-military settings.

shown to prolong the time a given patient is in a shockable rhythm and limit the deterioration to a Non-shockable rhythm [24,25].

We also found high rates of AED use prior to EMS arrival on military bases. This is important because early AED use has been linked with im- proved survival [26]. There has been an emphasis in recent years on equipping military settings with an adequate number of AEDs that can be easily utilized in the event of an emergency [15-17,19]. The relatively-high rates of pre-EMS AED use likely reflects this emphasis, as well as the relative abundance of individuals trained in AED use. In- terestingly, we found a noticeable difference in the rates at which return of spontaneous circulation (ROSC) was achieved across both cohorts, but this difference was not quite statistically significant. It is certainly possible that a larger sample size would yield statistical significance, es- pecially if the difference observed remains.

There has been literature examining the topic of cardiac arrest and sudden cardiac death on military bases in the past. First, it is important to mention that not all cardiac arrests on military bases involve sworn military members. Rather, cardiac arrests on military bases can involve non-military personnel, including contractors, civilian personnel, and family members [16]. Having said that, it is likely that many cardiac ar- rests on military bases involved service members. This is notable for a few reasons. For one, research indicates sudden cardiac death among service members is frequently caused by physical exertion and is usu- ally attributable to morphological or structural abnormalities [27,28]. This is different from the several autopsy studies showing sudden car- diac death in the non-military population is generally acquired (eg. cor- onary atherosclerosis or acquired cardiomyopathy) [29,30]. Second, service members have to undergo strict medical screenings and fre- quently take part in vigorous physical activity [27]. This means that the fitter individuals on a military base may already be more likely to survive a cardiac arrest than members of the general public, who may be older, more sedentary, and have more comorbidities.

There are several limitations with our study. Chiefly, there is a low Incidence of cardiac arrests on military bases, which has been a limita- tion faced by other studies on the topic [27,31]. Second, since EMS data does not always link with hospital data, we cannot ascertain rates of neurologically-intact recovery or survival to hospital discharge. That being said, our study makes a novel comparison between cardiac arrests on military bases and cardiac arrests in non-military settings. Further research should explore the topic of cardiac arrest on military bases with the aim of identifying strategies that may provide utility within civilian settings.

Funding

None.

Parameter Military

Settings (n = 60)

Non-military Settings

(n = 202,605)

CRediT authorship contribution statement

CPR Prior to EMS Arrival* 85.0% 63.1%

AED Use Prior to EMS Arrival* 55.0% 28.4% Shockable First-Monitored Arrest Rhythm* 46.7% 20.6%

Aditya C. Shekhar: Writing - original draft, Methodology, Formal analysis, Data curation, Conceptualization. Manu Madhok: Writing - original draft, Methodology, Conceptualization. Teri Campbell: Writing

Documented ROSC Achievement by EMS Male Sex* Patient race/Ethnicity	41.7% 81.7%	32.2% 63.8%	- review & editing, Conceptualization. Ira J. Blumen: Writing - original draft, Supervision, Methodology, Conceptualization. Richard M. Lyon:
White	53.3%	55.9%	Writing - review & editing, Supervision. N. Clay Mann: Writing -
Black/African American	16.7%	15.3%	review & editing, Validation, Supervision, Data curation.
Hispanic/Latino	10.0%	6.7%
Other/Not Recorded	21.7%	22.7%
Patient Age			Declaration of Competing Interest

None.

Under 18 Years	3.3%	2.2%
18-30 Years*	26.7%	4.4%
31-50 Years	20.0%	14.5%
51-70 Years	41.7%	38.1%
Older than 71 Years*	6.7%	40.1%

A table comparing witnessed cardiac arrests on both military bases and in non-military settings. Statistical significance based on p < 0.05 (two-tailed) is indicated by an asterisk.

References

1. Becker LB, Aufderheide TP, Graham R. Strategies to improve survival from cardiac arrest: a report from the Institute of Medicine. JAMA. 2015 Jul 21;314(3):223-4.
2. Girotra S, van Diepen S, Nallamothu BK, Carrel M, Vellano K, Anderson ML, et al. Re- gional variation in out-of-hospital cardiac arrest survival in the United States. Circu- lation. 2016 May 31;133(22):2159-68.
3. Virani SS, Alonso A, Benjamin EJ, Bittencourt MS, Callaway CW, Carson AP, et al. Heart disease and stroke statistics-2020 update: a report from the American Heart Association. Circulation. 2020 Mar 3;141(9):e139-596.
4. Sasson C, Rogers MA, Dahl J, Kellermann AL. Predictors of survival from out-of- hospital cardiac arrest: a systematic review and meta-analysis. Circ Cardiovasc Qual Outcomes. 2010 Jan;3(1):63-81.
5. Nolan J, Soar J, Eikeland H. The chain of survival. Resuscitation. 2006 Dec 1;71(3) 270-1.
6. Adabag S, Hodgson L, Garcia S, Anand V, Frascone R, Conterato M, et al. Outcomes of sudden cardiac arrest in a state-wide integrated resuscitation program: results from the Minnesota resuscitation consortium. Resuscitation. 2017 Jan 1(110):95-100.
7. Gul SS, Cohen SA, Becker TK, Huesgen K, Jones JM, Tyndall JA. Patient, neighborhood, and spatial determinants of out-of-hospital cardiac arrest outcomes throughout the chain of survival: a community-oriented multilevel analysis. Prehosp Emerg Care. 2020 May 3;24(3):307-18.
8. Moon S, Bobrow BJ, Vadeboncoeur TF, Kortuem W, Kisakye M, Sasson C, et al. Dis- parities in bystander CPR provision and survival from out-of-hospital cardiac arrest according to neighborhood ethnicity. Am J Emerg Med. 2014 Sep 1;32(9):1041-5.
9. Rivera NT, Kumar SL, Bhandari RK, Kumar SD. Disparities in survival with bystander CPR following cardiopulmonary arrest based on neighborhood characteristics. Emerg Med Int. 2016 Jan 1:2016.
10. Starks MA, Schmicker RH, Peterson ED, May S, Buick JE, Kudenchuk PJ, et al. Associ- ation of neighborhood demographics with out-of-hospital cardiac arrest treatment and outcomes: where you live may matter. JAMA Cardiol. 2017 Oct 1;2(10):1110-8.
11. Chan PS, McNally B, Vellano K, Tang Y, Spertus JA. Association of neighborhood race and income with survival after out-of-hospital cardiac arrest. J Am Heart Assoc. 2020 Feb 18;9(4):e014178.
12. Shekhar AC, Mercer C, Ball R, Blumen I. Persistent racial/Ethnic disparities in out-of- hospital cardiac arrest. Ann Emerg Med. 2021 Aug 1;78(2):314-6.
13. Shekhar AC, Campbell T, Mann NC, Blumen IJ, Madhok M. Age and racial/ethnic dis- parities in Pediatric out-of-hospital cardiac arrest. Circulation. 2022 Apr 19;145(16): 1288-9.
14. Shekhar A, Madhok M, Campbell T, Mann NC, Blumen I. Distinctive features of out- of-hospital cardiac arrests on military bases: a Nationwide analysis. J Am Coll Cardiol. 2022 Mar 8;79(9_Supplement):23.
15. Contreras L. Public access defibrillation program can save lives. Nellis Air Force Base. 2011 Feb 11.
16. Kresge P. Ohio National Guard Soldiers use AED equipment, swift action to save life NationalGuard.mil. 2012 Mar 26.
17. Potter CE. Public access defibrillator program. Air Force Instr. 2014 Jun 5:44-177.
18. Linde AS, Kunkler K. The evolution of medical training simulation in the US military. Med Meets Virtual Real. 2016;22:209-14.
19. Buckley AM, Cox AT, Rees P. Shocking the system: AEDs in military resuscitation. BMJ Mil Health. 2018 Aug 1;164(4):297-301.
20. Griffin MT. Have a Heart, Learn CPR. Army.mil; 2019 Feb 28.
21. Mann NC, Kane L, Dai M, Jacobson K. Description of the 2012 NEMSIS public-release research dataset. Prehosp Emerg Care. 2015 Apr 3;19(2):232-40.
22. Ehlers J, Fisher B, Peterson S, Dai M, Larkin A, Bradt L, et al. Description of the 2020 NEMSIS public-release research dataset. Prehosp Emerg Care. 2022 May 18:1-5.
23. Friedman J, Mann NC, Hansen H, Bourgois P, Braslow J, Bui AA, et al. Racial/ethnic, social, and geographic trends in overdose-associated cardiac arrests observed by US emergency medical services during the COVID-19 pandemic. JAMA Psychiat. 2021 Aug 1;78(8):886-95.
24. Nishiuchi T, Hiraide A, Hayashi Y, Uejima T, Morita H, Yukioka H, et al. Incidence and survival rate of bystander-witnessed out-of-hospital cardiac arrest with cardiac eti- ology in Osaka, Japan: a population-based study according to the Utstein style. Resuscitation. 2003 Dec 1;59(3):329-35.
25. Song J, Guo W, Lu X, Kang X, Song Y, Gong D. The effect of bystander cardiopulmo- nary resuscitation on the survival of out-of-hospital cardiac arrests: a systematic re- view and meta-analysis. Scand J Trauma Resusc Emerg Med. 2018 Dec;26(1) 1-0.
26. Holmberg MJ, Vognsen M, Andersen MS, Donnino MW, Andersen LW. Bystander au- tomated external defibrillator use and clinical outcomes after out-of-hospital cardiac arrest: a systematic review and meta-analysis. Resuscitation. 2017 Nov 1;120: 77-87.
27. Eckart RE, Scoville SL, Campbell CL, Shry EA, Stajduhar KC, Potter RN, et al. Sudden death in young adults: a 25-year review of autopsies in military recruits. Ann Intern Med. 2004 Dec 7;141(11):829-34.
28. Smallman DP, Webber BJ, Mazuchowski EL, Scher AI, Jones SO, Cantrell JA. Sudden cardiac death associated with physical exertion in the US military, 2005-2010. Br J Sports Med. 2016 Jan 1;50(2):118-23.
29. Virmani R, Burke AP, Farb A. Sudden cardiac death. Cardiovasc Pathol. 2001 Sep 1;10

(5):211-8.

1. Adabag AS, Peterson G, Apple FS, Titus J, King R, Luepker RV. Etiology of sudden death in the community: results of anatomical, metabolic, and genetic evaluation. Am Heart J. 2010 Jan 1;159(1):33-9.
2. Phillips M, Robinowitz M, Higgins JR, Boran KJ, Reed T, Virmani R. Sudden cardiac death in air force recruits: a 20-year review. JAMA. 1986 Nov 21;256(19):2696-9.