Introduction:
External defibrillators are used for cardioversion and resuscitation after sudden cardiac arrest (SCA). External defibrillators are also required for emergency MRI (acute stroke, spinal trauma). Low-power (9 Joule) ICD RPDs [1], and MRI-conditional external defibrillator prototypes exist [2]. An RPD external defibrillator was constructed, consisting of a Zoll defibrillator integrated with a tetanizing unit. The tetanizing waveform slowly compressed chest musculature prior to the strong biphasic defibrillating pulse, reducing chest contraction during the biphasic pulse, the major pain source. This RPD system (Fig. 1A-D) was evaluated for pain reduction and defibrillation effectiveness in swine.
Method:
The tetanizing unit consisted of a programmable generator that delivered a triangular 1-KHz pulse of 250-2000msec duration and 10-100 Volt peak amplitude, and subsequently triggered the conventional defibrillator to send out standard short (8msec) powerful (20-400 J) biphasic pulses. Forward limb motion (Fig. 1E), an established pain measure [3], was evaluated by measuring limb acceleration, acceleration rate and work (energy). 5 swine were arrested electrically and then defibrillated. RPD was repeated 15-20 times/swine, varying tetanizing parameters and biphasic energy.
Results:
Fig. 1F-H compare an RPD defibrillation and equivalent biphasic defibrillation, showing smaller accelerations and acceleration rates. Fig. 1J shows work results, at 30-200J biphasic energy, demonstrating an 83
+
15% limb work reduction with the RPD waveforms. Optimal tetanizing parameters were 15-25V amplitude and 500-750msec duration. Rhythm recovery for RPD and conventional defibrillation was identical.
Conclusions:
Reduced pain defibrillation may allow cardioversion without anesthesia and faster defibrillation after SCA.
References:
[1] Hunter DW 2016. [2] Schmidt EJ 2016. [3] Boriani G, 2005.
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