Clinical paperSensitivity and specificity of two different automated external defibrillators☆
Introduction
Ventricular tachyarrhythmias, i.e. ventricular fibrillation (VF) and ventricular tachycardia (VT), constitute the most common cause of sudden cardiac death [1]. However, these patients have a good prognosis if treated with prompt defibrillation [2], [3], [4], [5]. Therefore, major efforts are made to decrease time from cardiac arrest (CA) to defibrillation, by using automated external defibrillators (AEDs) [5], [6], [7].
Unfortunately, not delivering a prompt shock to a patient suffering VT or VF could be fatal [8]. In addition, delivering a shock to a patient with a non-shockable rhythm may be harmful [9] and leads to increased levels of biomarkers of myocardial injury [10]. Even when performed by professionals, correct manual distinction between shockable and non-shockable rhythms is difficult, especially during CA situations [11], and puts high demands on training and experience.
The AED uses a rhythm analysis algorithm (RAA) to differentiate between shockable and non-shockable rhythms. The RAA guides medical professionals and allows laymen to provide prompt, life-saving defibrillation. Therefore, RAAs need to have a high sensitivity to detect shockable rhythms, but also a high specificity to identify non-shockable rhythms. Performance criteria in terms of sensitivity and specificity have been established [12] but real life performance data are sparse.
Accuracy of RAA (sensitivity and specificity) is affected e.g. by artifacts from chest compressions or rescue vehicle movements. It appears that moderate sensitivity problems are common, ranging from 2.7% in a study by Herlitz et al., to 19.0% in a study by MacDonald et al. On the other hand, problems with specificity are very rare (<1.0%) [13], [14]. However, we have recently reported several cases with spurious shocks for non-shockable rhythms [15]. In addition, another recent study from Belgium, which included 837 rhythm analyses, found a higher proportion of specificity problems [8], compared to previous research. These reports indicate differences in AED performance when modern resuscitation guidelines, aiming at maximizing chest compression fraction, are used [6], [7]. The variability of previous results could also be an effect of differences in methodology or between the type of AED studied.
There is a lack of large more recent studies investigating AED performance. In addition, to the best of our knowledge, no study has compared different types of AEDs. Therefore, the aim of this study was to investigate sensitivity and specificity of two different AEDs.
Section snippets
Design
This study has a retrospective design and was approved by the Regional Ethical Review Board in Linköping, Sweden (No. 2014/365-31).
Sample and procedure
The study was conducted at a middle-sized (350 beds) hospital in the southeast of Sweden with a catchment area of 230,000 inhabitants. The hospital has a long routine of collecting, reviewing and documenting AED data files from in-hospital and out-of-hospital CA events.
According to guidelines [12], three investigators (JI, cardiology nurse, resuscitation
Characteristics of events
During the study period 240 events were included. The median age was 72 (q1-q3 = 62–83). The majority were men (n = 149, 62.1%) and most patients suffered their CA out-of-hospital (n = 150, 62.5%). More than half of the patients had a presumed cardiac aetiology (n = 131, 54.6%), but a minority (n = 60, 25.0%) had a shockable initial rhythm. There were no differences between AED A and AED B in event characteristics, except differences in CA location and a higher proportion of men treated with AED B (Table
Discussion
In total (for both AEDs) sensitivity and specificity were acceptable with regard to international guidelines, which stipulate >90% sensitivity for coarse VF, >99% for sinus rhythm and >95% for other non-shockable rhythms [12]. From a more general perspective, the RAAs could be considered having excellent accuracy [16]. However, significant differences in performance could be detected between the two different AEDs. A higher sensitivity of AED B was associated with a lower specificity, while a
Conclusion
There were significant differences in sensitivity and specificity between the two different AEDs. A higher sensitivity of AED B was associated with a lower specificity while a higher specificity of AED A was associated with a lower sensitivity. AED manufacturers should work to improve the algorithms in order to minimize the gap between sensitivity and specificity. In addition, AED use should always be reviewed with a routine for giving feedback to health care professionals, and medical
Conflict of interest statement
None of the authors have any conflicts of interest to declare.
Acknowledgement
We would like to thank Jean Stevenson-Ågren for reviewing the language.
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Cited by (10)
Optimizing outcomes after out-of-hospital cardiac arrest with innovative approaches to public-access defibrillation: A scientific statement from the International Liaison Committee on Resuscitation
2022, ResuscitationCitation Excerpt :It should also be noted that data in this study were derived from a limited number of device models; therefore, the results may not be generalizable to all AEDs, including newer defibrillators available on the market today. Other studies reporting sensitivities ranging from 84% to 91.2% suggest that there is room for improvement in the algorithms that AEDs use to detect shockable rhythms.145–147 More sophisticated filtering techniques are becoming available.
In-hospital cardiac arrest rhythm analysis by anesthesiologists: a diagnostic performance study
2023, Canadian Journal of Anesthesia
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A Spanish translated version of the abstract of this article appears as Appendixi n the final online version at http://dx.doi.org/10.1016/j.resuscitation.2017.09.009.