Analog-digital recording of current and voltage during high voltage DC shocks

Efficient on-line digitization is the prerequisite for computerized analysis of the electrical phenomena occurring during defibrillation. Conventional hardware presently provides only limited time resolution. The performance of various digitization rates for recording of voltage, current, and calculation of derived quantities like impedance, energy, and defibrillator capacitance was investigated. It was assessed both experimentally and by computer simulation of a trapezoidal discharge (of 9 msec duration into a constant resistive load of 50 omega with a defibrillator capacitance of 132 microF). The accuracy achieved with different digitization rates is given. For example, an accuracy of 1% for analog-digital conversion for impedance calculation during this kind of DC shock requires a sampling rate of 8 kHz without, and a rate of 1 kHz with linear interpolation to correct for the hardware dependent error due to sequential sampling.

Highly efficient analog-digital conversion of delivered voltage and current during DC shocks is available within the limits of conventional inexpensive hardware.