Impedance to transthoracic direct current discharge: a model for testing interface material

Area of Science:

• Biomedical Engineering
• Medical Device Testing

Background:

• Effective impedance of electrode gels is crucial for safe and efficient defibrillation and cardioversion.
• Variations in gel properties can impact energy delivery and patient outcomes.

Purpose of the Study:

• To develop and validate an in vitro method for assessing the relative impedance of electrode gels.
• To evaluate the suitability of commercially available electrode gels for defibrillation and cardioversion.

Main Methods:

• An in vitro testing chamber with 1-cm electrodes was constructed.
• A defibrillator delivering a half-sinusoidal waveform was used to measure impedance.
• Twelve electrode gels were tested with 10 measurements per gel.

Main Results:

• A significant variation in direct current discharge impedance was observed among commercially available electrode gels.
• Increasing gel impedance led to decreased delivered current and increased voltage-time interval.
• Many tested gels demonstrated impedance levels not suitable for defibrillation/cardioversion.

Conclusions:

• The developed in vitro method effectively screens electrode gel impedance.
• A substantial number of commercial electrode gels are inadequate for use in defibrillation and cardioversion.
• Gel impedance is a critical factor influencing the efficacy of external cardiac electrical therapies.