Estimation of current density distribution under electrodes for external defibrillation.
BACKGROUND
Transthoracic defibrillation is the most common life-saving technique for the restoration of the heart rhythm of cardiac arrest victims. The procedure requires adequate application of large electrodes on the patient chest, to ensure low-resistance electrical contact. The current density distribution under the electrodes is non-uniform, leading to muscle contraction and pain, or risks of burning. The recent introduction of automatic external defibrillators and even wearable defibrillators, presents new demanding requirements for the structure of electrodes.


RESULTS
Using the pseudo-elliptic differential equation of Laplace type with appropriate boundary conditions and applying finite element method modeling, electrodes of various shapes and structure were studied. The non-uniformity of the current density distribution was shown to be moderately improved by adding a low resistivity layer between the metal and tissue and by a ring around the electrode perimeter. The inclusion of openings in long-term wearable electrodes additionally disturbs the current density profile. However, a number of small-size perforations may result in acceptable current density distribution.


CONCLUSIONS
The current density distribution non-uniformity of circular electrodes is about 30% less than that of square-shaped electrodes. The use of an interface layer of intermediate resistivity, comparable to that of the underlying tissues, and a high-resistivity perimeter ring, can further improve the distribution. The inclusion of skin aeration openings disturbs the current paths, but an appropriate selection of number and size provides a reasonable compromise.
Krasteva
Vessela Tz
VT
Center for Biomedical Engineering, Bulgarian Academy of Sciences, Acad, G, Bonchev str, block 105 Sofia 1113, Bulgaria. vessika@clbme.bas.bg
Papazov
Sava P
SP
D002058:Burns, Electric / Q000209:etiology; D003196:Computer Graphics; D003198:Computer Simulation; D004553:Electric Conductivity; D004554:Electric Countershock / Q000009:adverse effects / Q000295:instrumentation* / Q000379:methods*; D017097:Electric Impedance; D004566:Electrodes; D004574:Electromagnetic Fields; D004867:Equipment Design; D020342:Finite Element Analysis; D006801:Humans; D008962:Models, Theoretical; D009119:Muscle Contraction; D010146:Pain / Q000209:etiology