Effect of Electromagnetic Interference on Automated External Defibrillator: Simulation Study with Literature Review

PURPOSE: Automated external defibrillators (AEDs) could not recommend shock for ventricular fibrillation in the presence of electromagnetic interference. The purpose of this study was to examine the effect of an induced electromagnetic field on performance of AED. METHODS: The intensity of magnetic waves from commercial electric mats was measured. Three AEDs were attached to the resuscitation manikin and the question of whether shock would be recommended for simulated electrocardiogram of VF or normal sinus rhythm was tested. The simulation was repeated 10 times under the influence of 0, 5, and 18 µT magnetic field or electric mat. Relevant literature studies on electromagnetic interference on AED were reviewed. RESULTS: The magnetic flux density from the electric mat was measured to 5.67-6.1 µT in warming phase, and 2.25-2.84 µT in maintenance phase. There was no false positive or false negative recommendation of shock under the influence of 0, 5, and 18 µT magnetic field or electric mat. However, one AED detected motion even in the stationary state. Among 11 studies from the literature search, five studies reported misinterpretation of AED. Minor errors including delayed analysis, motion artefact, and noise in speakers were reported from 6 studies. CONCLUSION: Although we could not reproduce false negative interpretation, AED made a mistake in confusing electromagnetic interference with motion artefact. Therefore, emergency providers should be cautious not to use AED close to household appliances or medical equipment inducing electromagnetic interference.

Ultrasonography Versus MRI for Diagnosing Acute Appendicitis During Pregnancy

PURPOSE: The purpose of this study is to compare the sensitivity, specificity, positive predictive value, and negative predictive value of ultrasonography versus magnetic resonance imaging (MRI) in evaluation of pregnant patients with clinically suspicious acute appendicitis. METHODS: This study was a retrospective cohort study. A total of 60 pregnant patients who presented to the emergency department with suspected appendicitis and underwent ultrasonography or MRI were included. The official interpretation reports and pathologic reports were extracted and analyzed. The sensitivity, specificity, positive predictive value, and negative predictive value were calculated for ultrasonography and MRI for diagnosis of acute appendicitis. We also calculated and compared area under the curve (AUC) of both diagnostic tests with the receiver operating characteristic (ROC) curve analysis. RESULTS: Among 60 patients, 43 (71%) underwent ultrasonography, 37 (61%) underwent MRI, and 20 (33%) underwent both diagnostic tests. Twenty patients were confirmed as pathologically-proven acute appendicitis. The sensitivity, specificity, positive predictive value, and negative predictive value of ultrasonography for diagnosing acute appendicitis were 67%, 77%, 53%, and 86%, while those of MRI were 100% for all parameters. In ROC analysis, the AUC was 0.656, respectively, for ultrasonography, and 1.000 for MRI (p value<0.0001). CONCLUSION: This study suggests that MRI is more accurate than ultrasonography for the diagnosis of acute appendicitis in pregnant women, especially when the appendix is invisible with ultrasonography.

Two Cases of Intoxication with Phentermine

Phentermine has been widely used as an appetite suppressant since 2004 in Korea. The authors experienced two cases of acute phentermine overdose and report with the literature review. A 36-year-old man and a 24-year-old woman presented together to the emergency department with taking 13 tablets (390 mg) of phentermine 16 hours ago. They had tachycardia, hypertension and complained visual symptoms, nausea, insomnia and anxiety. These symptoms were resolved by conservative management.

Two Cases of Intoxication with Phentermine

Phentermine has been widely used as an appetite suppressant since 2004 in Korea. The authors experienced two cases of acute phentermine overdose and report with the literature review. A 36-year-old man and a 24-year-old woman presented together to the emergency department with taking 13 tablets (390 mg) of phentermine 16 hours ago. They had tachycardia, hypertension and complained visual symptoms, nausea, insomnia and anxiety. These symptoms were resolved by conservative management.

L-carnitine vs Extracorporeal Elimination for Acute Valproic acid Intoxication: A Systematic Review

PURPOSE: The purpose of this study is to review the evidence comparing the efficacy and safety between L-carnitine and extracorporeal elimination therapy in the management of acute valproic acid L-carnitine vs Extracorporeal Elimination for Acute Valproic acid Intoxication METHODS: PubMed, Embase, Cochrane library, Web of Science, KoreaMed, KMbase, and KISS were searched, using the terms carnitine and valproic acid. All studies, regardless of design, reporting efficacy or safety endpoints were included. Reference citations from identified publications were reviewed. Both English and Korean languages were included. Two authors extracted primary data elements including poisoning severity, presenting features, clinical management, and outcomes. RESULTS: Thirty two articles including 33 cases were identified. Poisoning severity was classified as 3 mild, 11 moderate, and 19 severe cases. Nine cases were treated with L-carnitine while 24 cases received extracorporeal therapy without L-carnitine. All patients except one expired patient treated with hemodialysis recovered clinically and no adverse effects were noted. A case report comparing two patients who ingested the same amount of valproic acid showed increased ICU stay (3 vs 11 days) in case of delayed extracorporeal therapy. CONCLUSION: Published evidence comparing L-carnitine with extracorporeal therapy is limited. Based on the available evidence, it is reasonable to consider L-carnitine for patients with acute valproic acid overdose. In case of severe poisoning, extracorporeal therapy would also be considered in the early phase of treatment.

Accuracy of the Automatic External Defibrillator on an Electric Mattress: Simulation Study

PURPOSE: The accuracy of the automated external defibrillator (AED) is susceptible to environmental factors such as vibration, motion artifacts, and electromagnetic interference (EMI). The purpose of this study was to evaluate whether the EMI produced by an electric mattress can affect the performance of AEDs. METHODS: Four commercially available AEDs were evaluated under four ECG rhythm settings (normal sinus rhythm, asystole, ventricular fibrillation, and ventricular tachycardia) with or without an electric mattress. The sensitivity, specificity, positive predictable value, negative predictable value, and accuracy of AEDs were calculated to differentiate shockable from nonshockable rhythms. Times required to interpret the ECGs were checked with and without an electric mattress. RESULTS: A total of 320 tests were recorded, and each AED was tested a total of 80 times. Depending on the AED model used on an electric mattress, sensitivity ranged from 55% to 90% with a specificity of 100%, and accuracy ranged from 77.5% to 95%. For some AEDs, sensitivity was reduced compared to the control. Although there was no significant difference in times required to interpret ECG signals with or without an electric mattress, some AEDs detected a relatively small interference as motion artifacts when an electric mattress was used. All recorded ECG rhythms on an electric mattress showed baseline artifacts and these artifacts lessened with increasing distance from an electric mattress. CONCLUSION: This study suggests that an electric mattress could affect the shockable rhythm performance of some AEDs. Electromagnetic interference generated by an electric mattress could interfere with the ability of some commercial AEDs to correctly interpret stimulated ECG rhythms and provide appropriate defibrillation.

Accuracy of the Automatic External Defibrillator on an Electric Mattress: Simulation Study

PURPOSE: The accuracy of the automated external defibrillator (AED) is susceptible to environmental factors such as vibration, motion artifacts, and electromagnetic interference (EMI). The purpose of this study was to evaluate whether the EMI produced by an electric mattress can affect the performance of AEDs. METHODS: Four commercially available AEDs were evaluated under four ECG rhythm settings (normal sinus rhythm, asystole, ventricular fibrillation, and ventricular tachycardia) with or without an electric mattress. The sensitivity, specificity, positive predictable value, negative predictable value, and accuracy of AEDs were calculated to differentiate shockable from nonshockable rhythms. Times required to interpret the ECGs were checked with and without an electric mattress. RESULTS: A total of 320 tests were recorded, and each AED was tested a total of 80 times. Depending on the AED model used on an electric mattress, sensitivity ranged from 55% to 90% with a specificity of 100%, and accuracy ranged from 77.5% to 95%. For some AEDs, sensitivity was reduced compared to the control. Although there was no significant difference in times required to interpret ECG signals with or without an electric mattress, some AEDs detected a relatively small interference as motion artifacts when an electric mattress was used. All recorded ECG rhythms on an electric mattress showed baseline artifacts and these artifacts lessened with increasing distance from an electric mattress. CONCLUSION: This study suggests that an electric mattress could affect the shockable rhythm performance of some AEDs. Electromagnetic interference generated by an electric mattress could interfere with the ability of some commercial AEDs to correctly interpret stimulated ECG rhythms and provide appropriate defibrillation.