Pre-shock high-frequency low-amplitude impedance measurements cannot predict intra-shock impedance with high accuracy, showing differences up to 15-17% using biphasic pulses in patients.
Effect estimate: up to 15-17% difference
Transthoracic electrical defibrillation is administered by high voltages and currents applied through large size electrodes. Therefore, the defibrillator load impedance becomes an essential factorfor the efficacy of the procedure. Attempts at prediction of transthoracic impedance by pre-shock measurement with low-amplitude high-frequency current have yielded apparently promising results. A reassessment was undertaken of the comparison between transthoracic impedance measured over a wide frequency range (bioimpedance spectroscopy) and measured during the shock. An estimation of the possibilities for pre-shock 'prediction ' of the impedance was performed, to allow adequate selection of the defibrillation energy or current with the intention of increasing the possibility for positive results with the first shock. Data were obtained from experimental fibrillation/defibrillation cycles on dogs andfrom cardioversion of atrial fibrillation or flutter in patients. The final results suggest that high-frequency low-amplitude impedance measurements cannot predict the corresponding value during the shock with very high accuracy, as differences up to 15-17% were found using biphasic pulses in patients. However, the method can be used for approximate assessments.
Vessela Krasteva (Mon,) conducted a other in Atrial fibrillation or flutter. Pre-shock high-frequency low-amplitude impedance measurement vs. Impedance measured during the shock was evaluated on Difference between pre-shock and intra-shock impedance (up to 15-17% difference). Pre-shock high-frequency low-amplitude impedance measurements cannot predict intra-shock impedance with high accuracy, showing differences up to 15-17% using biphasic pulses in patients.