Operating instructions

LIFEPAK 500 Automated External Defibrillator Operating Instructions 5-19

Maintenance

5 Maintenance

Ventricular Tachycardia

Seventy-two episodes of ventricular tachycardia (VT), induced in 62 patients, were treated with

randomized shocks. High rates of conversion were observed with biphasic and monophasic shocks.

Sample sizes were too small to statistically determine the relationship between success rates of the

waveforms tested.

Conclusions

In this double-blinded study, the efficacy of the 200J BTE shocks was demonstrated to be at least

equivalent to the efficacy of 200J MDS shocks for defibrillation of short duration, electrically-induced

VF. However, the comparison of efficacy of 130J biphasic and 200J monophasic shocks for VF was

inconclusive. All waveforms tested provided a high rate of termination of VT. The VT sample sizes were

too small to statistically determine the relationship between VT success rates of the waveforms tested.

Compared to conventional shocks for VF, we found no positive or negative effect of biphasic shocks for

VF on hemodynamic parameters following the defibrillating shock. It is possible that, compared to 200J

monophasic shocks, 200J biphasic shocks will in some cases enable earlier termination of VF.

Therefore, we conclude that biphasic shocks for VF delivered at conventional energy levels have the

potential to improve outcome in resuscitation of patients with cardiac arrest.

Shock

Ventricular Tachycardia

1st Shock Success

Exact 95% Confidence Interval

200J MDS 26/28 (93%) 77–99%

200J BTE 22/23 (96%) 78–100%

130J BTE 20/21 (95%) 76–100%