Hello
I have located several explanations of these concepts on the web,
including the current levels that will cause fibrillation.
From "Electrical Safety," hosted by Queensland University of
Technology:
"Macroshock
This is defined as the passage of current from one part of the body to
another, especially from arm to arm and therefore through the heart.
The current is the most important factor. (A high-voltage low-current
shock is not dangerous).
... 100 -300 mA, Ventricular fibrillation, respiration OK ...
Microshock
Current flows directly through the electrically sensitive myocardium,
the safe limit is 10mA. 20mA can be fatal, causing ventricular
fibrillation. Microshock applies to all cases where an electrode or
catheter is situated near or in the heart, for example a pacing
electrode or a pressure-monitoring catheter. Leakage currents can pass
through the heart, even if an instrument has been isolated."
Source: "Electrical Safety"
From Faculty of Science, Queensland University of Technology
http://www.sci.qut.edu.au/physci/units/physics/pcb504/textbook/chapter12.doc
From Dr Jensen's Board Prep:
Fibrillation: Macroshock "100 mA ( milliamps ) "; Microshock: "100 uA
( microamps )"
"Macroshock: The amount of current applied to the outside of the
body.
Microshock: The amount of current applied to the inside of the body."
Source: Dr. Jensen Anesthesiology Board P.R.E.P.
http://www.boardprep.com/pain/questions.html
From Prof. Peter N. Steinmetz's "Bioelectricity and
Bioinstrumentation":
"What is the difference between a microshock and a macroshock?
Macroshock
This is defined as the passage of current from one part of the body to
another, especially from arm to arm and therefore through the heart.
The current is the most important factor. (A high-voltage low-current
shock is not dangerous). Microshock
Current flows directly through the electrically sensitive myocardium,
the safe limit is 10 mA. 20mA can be fatal, causing ventricular
fibrillation. Microshock applies to all cases where an electrode or
catheter is situated near or in the heart, for example a pacing
electrode or a pressure-monitoring catheter. Leakage currents can pass
through the heart, even if an instrument has been isolated."
Source: Problem Set #11
Prof. Peter N. Steinmetz's "Bioelectricity and Bioinstrumentation"
Hosted by University of Minnesota:
http://www.bml.umn.edu/bmen3201/PS11solution.pdf
search strategy: microshock, macroshock, fibrillation, current
I hope this helps. |
