Sensitivity and Specificity of Two Different Automated External Defibrillators (AED) Used in in-Hospital and Out-Of-Hospital Cardiac Arrest

Purpose: To investigate the performance of two different types of automated external defibrillators (AED) in out-of-hospital and in-hospital cardiac pulmonary resuscitation (CPR). Performance criteria in terms of sensitivity and specificity have been established (1) but real life data are sparse (2-5).

Material and Methods:Three investigators reviewed 2938 rhythm analyses performed by AED in 240 consecutive patients (38.3% women) suffering cardiac arrest between Januari 2011 and March 2015. The mean age was 70.1±17.0 (3 months – 104 years). Two different AED were used (AED A n=105, AED B n=135) in-hospital (n=91) and out-of-hospital (n=149).

Results:Among 194 shockable rhythms, 17 (8.8%) were not recognized by AED A, while AED B recognized 100% (n=135) of shockable episodes (p<0.001). In AED A, 8 (47.1%) of these episodes were judged to be algorithm errors while 9 (52.9%) were caused by external artifacts. Among 1039 non-shockable rhythms, AED A recommended shock in 11 (1.0%), while AED B recommended shock in 63 (4.1%) of 1523 episodes (p<0.001). In AED A, 2 (18.2%) of these episodes were judged to be algorithm errors (AED B, n=40, 63.5%) while 9 (81.8%) were caused by external artifacts (AED B, n=23, 36.5%). Fine ventricular fibrillation was analyzed as a separate category since guidelines do not recommend shock in these cases. AED A advised shock in 24 (80%) of 30 episodes, while AED B advised shock in 8 (47%) of 17 episodes (p<0.027).

Conclusions: Significant differences in performance could be detected between two different AED. 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. Caregivers should be aware of the specific shortcomings of the device they are using. AED manufacturers should try to improve the algorithms in order to minimize the gap between sensitivity and specificity.