a b s t r a c t

Billions of travelers pass through airports around the world every year. Airports are a relatively common location for sudden cardiac arrest when compared with other public venues. An increased Incidence of cardiac arrest in airports may be due to the large volume of movement, the stress of travel, or adverse effects related to the phys- iological environment of airplanes. Having said that, airports are associated with extremely high rates of witnessed arrests, bystander interventions (eg. CPR and AED use), shockable arrest rhythms, and survival to hos- pital discharge. Large numbers of people, a high density of public-access AEDs, and on-site emergency medical services (EMS) resources are probably the major reasons why cardiac arrest outcomes are so favorable at airports. The success of the Chain of survival found at airports may imply that applying similar practices to other public venues will translate to improvements in Cardiac arrest survival. Airports might, therefore, be one model of car- diac arrest preparedness that other public areas should emulate.

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1. Introduction

Sudden cardiac arrest is more likely to occur in public areas with high volumes of movement and traffic [1,2]. Commercial airports have, there- fore, been associated with a relatively high incidence of cardiac arrest [1,3]. Having said that, large commercial airports have also been used to evaluate strategies for improving cardiac arrest survival – some have even referred to airports as laboratories in the out-of-hospital cardiac ar- rest chain of survival [4]. The lessons learned from the management of cardiac arrest in airports have considerable relevance to other settings in which cardiac arrest may take place. This brief narrative review will summarize a few key aspects about cardiac arrest in airports and de- scribe how research examining cardiac arrest in airports has implications for other areas in resuscitation and emergency care research.

1. Increased incidence of sudden cardiac arrest in airports

Several studies indicate that airports may face a higher rate of car- diac arrest than other public areas, most likely because billions of pas- sengers move through airports every year [1,3,5]. Becker et al. [1] found that the Seattle-Tacoma International Airport had the highest

* 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).

incidence of cardiac arrest among public places studied between Janu- ary 1990 and December 1994; 3.1% of public-location arrests in their study (n = 1130) were at the airport. In a study of the Victorian Ambu- lance Cardiac Arrest Registry, Lijovic et al. [5] concluded that the inter- national airport had an extremely high burden from cardiac arrest as compared to other public locations; 12% of bystander-defibrillated ar- rests in their study occurred at the airport, the most of any single public location. Marijon et al. [2] described why this might be the case: using cardiac arrest data from Paris between 2000 and 2010, they report a strong association between the incidence of cardiac arrest and popula- tion movement (p < 0.001).

Another potential reason why airports may face an elevated burden from cardiac arrest is the stress associated with travel. Travel is associ- ated with an increase in psychological and physiological stress [6,7]. In- creased physiological stress has been shown to increase a person’s risk of sudden death through a number of different mechanisms [8]. Thus, the stress of travel may have precipitated cardiac arrests in individuals already at high risk of having a cardiac arrest in the first place.

Another possible explanation for the elevated risk of cardiac arrest in

airports is the physiological environment of an airplane, which might also increase the risk of a cardiac arrest, either in-flight or after landing at the arrival airport. The passenger cabins of commercial airplanes are pressurized, but the partial pressure of oxygen is not equivalent to that of sea level – typically ranging between a pressure altitude of 6000 to 8000 f. (1829-2438 m) [9,10]. Passengers and crew, therefore,

https://doi.org/10.1016/j.ajem.2022.07.006

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experience mild hypoxia during flight, which has been shown to affect their ability to perform strenuous activity and may result in saturations

<80% in healthy passengers [11]. Commercial airplane cabins have also been associated with low humidity, poor air quality, and even ozone ex- posure [12-14]. Air travel has also been implicated as a significant cause of deep-vein thrombosis, most likely because passengers must remain sedentary for multiple hours on an airline flight [15-17]. Lastly, poten- tially limited access to food and water during a flight may lead to elec- trolyte imbalances, dehydration, or hypoglycemia, all of which can lead to cardiac arrest [18,19]. Each of these factors may elevate an indi- vidual’s risk of cardiac arrest.

1. Significantly improved cardiac arrest survival at airports

Airports have been associated with high rates of cardiac arrest sur- vival. For example, Chatterjee et al. [20] reported 44% survival to hospi- tal discharge for cardiac arrests at Seattle-Tacoma International Airport between January 2004 and December 2019, and Nielsen et al. [22] re- ported 56.5% survival to hospital discharge for cardiac arrests at Copen- hagen International Airport between May 2015 and May 2019. These are more than double what has been traditionally seen with general out-of-hospital cardiac arrest [21]. This high cardiac arrest survival re- flects the efficacy and importance of early recognition, prompt by- stander intervention, availability of AEDs, and rapid response by EMS.

1. Airports and chain of survival part 1: Bystander interventions.

One of the most critical components of successful management of out-of-hospital cardiac arrest is the chain of survival [23]. The Chain of Survival concept highlights the importance of early recognition and ac- tivation of emergency response, early CPR and defibrillation, and opti- mized post-resuscitation care in facilitating good outcomes for cardiac arrest. The airport environment facilitates the chain of survival because of the large number of people present, which increases the likelihood that an arrest will be witnessed. Chatterjee et al. [20] reports 89% of car- diac arrests at Seattle-Tacoma International Airport were bystander- witnessed arrests. In contrast, the multicenter Resuscitation Outcomes Consortium (ROC) found only one-third of general out-of-hospital car- diac arrests were witnessed [24]. Witnessed arrests result in quicker bystander resuscitation (eg. CPR and AED use) and more-prompt activation of emergency response resources.

High rates of pre-EMS CPR and AED use by bystanders have been ob- served at airports. Chatterjee et al. [20] found that 78% who experienced cardiac arrest at Seattle-Tacoma International Airport received pre-EMS CPR and 55% had an AED applied on them prior to EMS arrival. Nielsen et al. [22] reported similar results for cardiac arrests at Copenhagen In- ternational Airport: 91.3% of arrests were witnessed, 73.9% received CPR prior to EMS arrival, and 43.5% had an AED applied prior to EMS arrival. In France, 52.4% of cardiac arrest victims at 19 airports between July 2011 and September 2015 had an AED applied by bystanders [25].

The rates of pre-EMS CPR and pre-EMS AED use in airports is signif- icantly higher than in other locations. For instance, nationally- representative EMS data in the United States indicate only half of car- diac arrest victims receive CPR prior to ambulance arrival [26]. Similarly, just 3.8% of cardiac arrest victims in Copenhagen between October 2011 and September 2013 and under 2% of cardiac arrest victims in Paris be- tween 2011 and 2014 received pre-EMS AED use by bystanders [27,28]. The significant number of people in an airport likely means that there is a high likelihood someone within close proximity to a cardiac arrest vic- tim knows how to perform CPR or use an AED.

1. Airports and chain of survival part 2: Public-access AEDs and emergency preparedness at airports

Some of the earliest trials evaluating the effectiveness of public- access AEDs took place in airports, and the success of these trials was

used to promote public-access AEDs in other locations [1,29]. For in- stance, one study across three Chicago airports found, among 18 pa- tients with ventricular fibrillation over a two-year period between June 1999 and May 2001, 14 received prompt defibrillation by by- standers, 11 were successfully resuscitated, and 8 even regained con- sciousness prior to hospital admission [29].

Prompt defibrillation allows shockable arrhythmias to be corrected before they deteriorate to a nonshockable rhythm and is associated with a dramatic improvement in survival [30,31]. Bystander CPR also helps to minimize the risk of deterioration to nonShockable rhythms [32,33]. Studies examining cardiac arrest at airports report high rates of shockable rhythms: 72% in Seattle-Tacoma International Airport

[20] and 52.2% in Copenhagen International Airport [22]. By compari- son, analyses of general out-of-hospital cardiac arrests suggest under 20% are initially shockable at the time of EMS arrival [28,34]. Increased rates of shockable cardiac arrest rhythms at airports likely reflect high rates of pre-EMS CPR and AED use, as well as decreased intervals from arrest onset to first assessment of arrest rhythm.

Another important factor is the presence of dedicated EMS resources

at airports or within airport terminals. Many large international airports have dedicated on-site EMS crews who can respond to medical emer- gencies in the terminal or onboard arriving aircraft [35,36]. The pres- ence of dedicated EMS crews at the airport decreases response time for cardiac arrest patients, thereby improving chances of survival [35,37]. For example, at Boston’s Logan International Airport, airport fire rescue crews were able to respond to cardiac arrests in an average of 2 min, and First responders at Copenhagen International Airport usu- ally were able to arrive within 3 min [22,37]. Additionally, other forms of emergency preparedness in airports – such as a high concentration of security officers and comprehensive video surveillance – assets can also be useful for promoting optimal outcomes for cardiac arrest.

1. Conclusions and implications for resuscitation research

Given their association with improved survival after cardiac arrest, airports might be an ideal model of cardiac arrest preparedness that other public areas should strive to emulate, and there are several poten- tial areas for future research. Firstly, much of the current research has focused on large, international airports: examining smaller, regional air- ports would help to determine whether the trends predominantly iden- tified in large airports hold true. Secondly, the chains of survival in place at airports should be studied in other public areas, such as gyms, sports arenas, shopping centers, and casinos [38-40]. The success of the chain of survival found at airports likely means applying similar practices to other public venues will translate to improvements in cardiac arrest survival.

Funding

None.

Credit authorship contribution statement

Aditya C. Shekhar: Writing – review & editing, Writing – original draft, Data curation, Conceptualization. Keith J. Ruskin: Writing – review & editing, Writing – original draft, Data curation.

Declaration of Competing Interest

The authors of this manuscript have no relevant conflicts of interest to disclose.

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