ESTIMATING THE 95-PERCENT EFFECTIVE DEFIBRILLATION DOSE

Minimum squared error (MinSE) testing protocols and a MinSE estimator are presented which accurately estimate the voltage that defibrillates 95% of the time (the ED95). The MinSE experimental procedures, presen ted in the form of lookup tables, detail the response to successful an d unsuccessful trials. The lookup tables also show the ED95 estimates calculated from the observed results using the MinSE estimator. Two as sumptions are required to develop the look-up tables: 1) the dose-resp onse curve, chosen using a statistical analysis of a retrospective sam ple, and 2) the distribution of the ED95's in the population. The MinS E estimator and experimental procedure are examined in a prospective s tudy of five dogs (19-25 kg, heart weights 139.3-236.9 gm) using nonth oracotomy implantable defibrillator electrodes and a biphasic defibril lation waveform (3.5 ms first phase, 2.0 ms second phase). Employing a n ED95 population distribution assumption applicable to most implantab le defibrillator electrodes and waveforms, e.g., the ED95 is between 0 .0 and 800.0 V, the measured rms error was 15% of the mean measured ED 95 for the MinSE, four test shock, ED95 estimates. If the protocols ar e designed with an ED95 population distribution assumption for animals of the same species and size, and defibrillation is constrained to on e electrode configuration and waveform, the estimates improve by 3.8%. Using techniques from the Bayesian statistics literature, the MinSE a pproach can be extended to a variety of defibrillation parameter estim ation problems.