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Estimation of current density distribution under electrodes for external defibrillation.

Krasteva VT, Papazov SP - Biomed Eng Online (2002)

Bottom Line: 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.However, a number of small-size perforations may result in acceptable current density distribution.The inclusion of skin aeration openings disturbs the current paths, but an appropriate selection of number and size provides a reasonable compromise.

View Article: PubMed Central - HTML - PubMed

Affiliation: Center for Biomedical Engineering, Bulgarian Academy of Sciences, Acad, G, Bonchev str, block 105 Sofia 1113, Bulgaria. vessika@clbme.bas.bg

ABSTRACT

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.

Method and 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.

Conclusion: 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.

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Current density distribution for a circular electrode with aeration openings. Right-side graphs – profiles along selected axes.
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Figure 7: Current density distribution for a circular electrode with aeration openings. Right-side graphs – profiles along selected axes.

Mentions: Electrodes of various shapes were designed, presumably more suitable for long-term wearing. Their respective shape and distribution profiles are shown in Figs. 7,8,9,10,11. The electrodes of Fig. 7, 10 and 11 are circular (5 cm radius; 0.5 mm interface layer thickness; ρ = 20 Ωm) with openings for improvement of skin aeration. We also simulated an electrode where the openings were replaced by conductive elements (Fig. 8). The four circular electrodes in Fig. 9, each surrounded by an additional ring, are of the same total area as the 5 cm radius circular electrode of Fig. 4. The "non-uniformity" coefficient of the current density distribution profile reaches very high values (K > 11) in a plane 0.5 mm below the interfacing gel. The performance of each electrode configuration was assessed also by the current distribution profile along an axis in the central region, at 50 mm depth in the 'thorax' domain (Fig. 12).


Estimation of current density distribution under electrodes for external defibrillation.

Krasteva VT, Papazov SP - Biomed Eng Online (2002)

Current density distribution for a circular electrode with aeration openings. Right-side graphs – profiles along selected axes.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC149376&req=5

Figure 7: Current density distribution for a circular electrode with aeration openings. Right-side graphs – profiles along selected axes.
Mentions: Electrodes of various shapes were designed, presumably more suitable for long-term wearing. Their respective shape and distribution profiles are shown in Figs. 7,8,9,10,11. The electrodes of Fig. 7, 10 and 11 are circular (5 cm radius; 0.5 mm interface layer thickness; ρ = 20 Ωm) with openings for improvement of skin aeration. We also simulated an electrode where the openings were replaced by conductive elements (Fig. 8). The four circular electrodes in Fig. 9, each surrounded by an additional ring, are of the same total area as the 5 cm radius circular electrode of Fig. 4. The "non-uniformity" coefficient of the current density distribution profile reaches very high values (K > 11) in a plane 0.5 mm below the interfacing gel. The performance of each electrode configuration was assessed also by the current distribution profile along an axis in the central region, at 50 mm depth in the 'thorax' domain (Fig. 12).

Bottom Line: 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.However, a number of small-size perforations may result in acceptable current density distribution.The inclusion of skin aeration openings disturbs the current paths, but an appropriate selection of number and size provides a reasonable compromise.

View Article: PubMed Central - HTML - PubMed

Affiliation: Center for Biomedical Engineering, Bulgarian Academy of Sciences, Acad, G, Bonchev str, block 105 Sofia 1113, Bulgaria. vessika@clbme.bas.bg

ABSTRACT

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.

Method and 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.

Conclusion: 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.

Show MeSH
Related in: MedlinePlus