The human factor in medical emergency simulation.

Medical errors rank high amongst leading causes of death. Especially in emergency care, when there is limited time to think, the "human factor", the interface between human action and the environmental system, has been recognized to be a critical part that determines the outcome. Recent models of human error are based on the principle that critical incidents are of multifactorial origin and reflect insufficiencies of the underlying system itself. The Human Simulation Center (HSC) was built specifically to train interaction between medical teams and to investigate the human factor in medical emergencies. In the following article we present "MevidIO", a live-monitoring and debriefing application framework. Developed for a full-scale simulation center designed to model error transduction in medical emergency care process chains, the framework integrates educational and scientific aspects.

Susceptibility of automated external defibrillators to train overhead lines and metro third rails.

INTRODUCTION: Immediate accessibility to automated external defibrillators (AED) is recommended for highly frequented public areas. In train terminals and metro stations electromagnetic interference (EMI) is present. In preparation for a public access defibrillation (PAD) programme in this environment possible effects on AED safety and accuracy were studied. METHODS: In typical public transportation settings 11 different AED models were bench tested for their sensitivity and specificity of ECG analysis with shockable and nonshockable rhythms provided by an ECG simulator. The devices were exposed to the electromagnetic interference of a rail system operating with 15 kV alternating current (ac) with a frequency of 16 2/3 Hz and a subway system powered with 750 V direct current (dc). AED cables were setup parallel and perpendicular to the tracks, the tests were carried out at 3 m distance from the rails in an empty station and with incoming trains. RESULTS: A total of 5280 tests were recorded, each device was tested a total of 480 times. Fifteen kilovolts 16 2/3 Hz ac interfered more than 750 V dc with the tachyarrhythmia detection systems (P < 0.0001). An AED setup with electrode cables perpendicular to track and power line reduced interference (P < 0.0001), while incoming trains had no significant effect on ECG analysis (P = 0.19). Depending on the AED model, sensitivity ranged from 60 to 100% and specificity from 54 to 100%, representing a positive likelihood-ratio from 1.3 to 241 and a negative likelihood-ratio from 0.7 to 0.0. In the public transportation setting tested, four AED models were unsuitable for automated defibrillation as these devices demonstrated an unacceptable performance in respect of accuracy and safety. In the train setting two devices performed with an accuracy of 57 and 65%. One AED recommended shocks for sinus rhythm at normal frequency. In the metro setting one AED did not advise shocks for ventricular tachycardia. CONCLUSION: Shock advisory systems of some AED models are susceptible to electromagnetic interference, especially in terminals with 15 kV 16 2/3 Hz ac power supplies. Interference is minimized, if patient position is parallel and electrode cables are perpendicular to overhead line. The choice of AED model for train or metro stations depends on its lack of susceptibility to typical electromagnetic interference.

Effect of digital cellular phones on tachyarrhythmia analysis of automated external defibrillators.

OBJECTIVES: Emergency services personnel, family members, laypersons or patients often carry and use mobile phones on sites of emergencies. As there are reported effects on implanted pacemakers and cardioverter defibrillators, the influence of digital cellular phones on automated external defibrillators was studied. METHODS: Twelve automated external defibrillator models were bench tested for their correct decision to or not to advise a shock, while being exposed to electromagnetic interference from a handheld cellular phone with 2 W or a portable cellular phone with 8 W transmitting power. The phones were programmed by a special subscriber identity module card to maximum output power with a carrier frequency of 906.2 MHz. The tests were conducted with a burst frequency of 217 Hz in speech mode and 2-8 Hz in discontinuous transmitting exchange mode. The sensitivity and specificity of electrocardiogram analysis systems were tested, with shockable and non-shockable rhythms provided by an electrocardiogram simulator and on two human subjects with normal sinus rhythm. RESULTS: A total of 8640 tests were recorded, each automated external defibrillator was tested a total of 720 times. The automated external defibrillators demonstrated a sensitivity of 100% and a specificity of 100%, representing a positive likelihood ratio of 8641 and a negative likelihood ratio of 0.000. In this setting all automated external defibrillators analysed correctly even under worst-case testing conditions, and performed excellently without any single failure. In some devices, voice prompts were distorted beyond comprehension, as the coil of the automated external defibrillator speaker received the pulsed signals. CONCLUSION: Shock advisory systems of automated external defibrillators are not susceptible to electromagnetic interference of 900 MHz cellular phones. Voice prompts, however, could be distorted by the operation of nearby digital mobile phones. During automated external defibrillator training this issue needs to be addressed.