tjt@ati.tis.llnl.gov (Tim Tessin) (03/13/88)
In article <5736@cit-vax.Caltech.Edu> flaig@cit-vlsi.UUCP (Charles M. Flaig) writes: > In article <1091@PT.CS.CMU.EDU> phd@SPEECH1.CS.CMU.EDU (Paul Dietz) writes: > >From "The Current that Kills" in October '87 IEEE Potentials > > > >1 - 3 mA Mild Sensation > >3 - ~10 mA Painful Sensation > >~10 - 30 mA Cannot let go. Current may increase to fatal level. > >30 - ~75 mA Breathing stops, often fatal. > >~75 - ~250 mA Heart fibrillation in 1.4 seconds, usually fatal. > >~250 mA - 4 A Heart stops during shock, may restart if current removed > > before death occurs. > >4 - 10A Severe burns, not fatal unless vital organs burned. > > Since most shock box circuits only deliver a single short pulse, I would > interpret this table to mean that shock boxes delivering 250mA are safe. > And possibly up to 4 A depending on how reliably a heart restarts after > a current pulse (after all, this is something they use to restart hearts > in an emergency). Just for fun, calculate the following data to see just what Johnny Gage and Roy DeSoto are playing around with. A typical DC Defibrillator used by your average Paramedic generates a maximum of 400 joules (watt-seconds) (actual delivered energy) for a duration of 16.66 msec (assume square wave). The trans-thoracic resistance (the resistance across your chest when the paddles and conductive gel are used) is anywhere from 30-100 Ohms (use 50 in your calculations). Note that these babys deliver ENERGY, so they are going to generate as much current and voltage as necessary to push the total energy through the resistance (the human). Calculate the instantaneous current and voltage. Tim Tessin
jay@splut.UUCP (Jay Maynard) (03/24/88)
From article <22066@tis.llnl.gov>, by tjt@ati.tis.llnl.gov (Tim Tessin): > Just for fun, calculate the following data to see just what Johnny Gage > and Roy DeSoto are playing around with. A typical DC Defibrillator used > by your average Paramedic generates a maximum of 400 joules (watt-seconds) > (actual delivered energy) for a duration of 16.66 msec (assume square wave). > The trans-thoracic resistance (the resistance across your chest when > the paddles and conductive gel are used) is anywhere > from 30-100 Ohms (use 50 in your calculations). Note that these babys > deliver ENERGY, so they are going to generate as much current and voltage > as necessary to push the total energy through the resistance (the human). > Calculate the instantaneous current and voltage. I get 1039 volts and 20 amps (roughly). Note that these numbers assume a transthoracic impedance of 50 ohms; the American Heart Association assumes 100 ohms (from the Advanced Cardiac Life Support textbook). At that impedance, you get 1470 volts and 15 amps. A hell of a shock, any way you cut it. Note that these are maximum figures, and based on the maximum output of modern defibrillators, 360 joules. This is enough energy to thoroughly fry the body if not used properly, and can have serious side effects (though not as serious as death if used correctly). Now you know why the body jerks when defibrillated, and why we're (supposed to be) extremely careful that nobody is touching the patient or anything metal the patient may be laying on while he gets shocked... I'm not sure about the suqre wave output, though; I'll have to get the manual for our Lifepak 5 out and look at it some. According to the manual, the open-circuit voltage across the paddles is 4200 volts. -- Jay Maynard, EMT-P, K5ZC...>splut!< | GEnie: JAYMAYNARD CI$: 71036,1603 uucp: {uunet!nuchat,academ!uhnix1,{ihnp4,bellcore,killer}!tness1}!splut!jay Never ascribe to malice that which can adequately be explained by stupidity. The opinions herein are shared by none of my cats, much less anyone else.