Date: Thu Feb 8 11:34:23 2007

Author: cablem

Subject: Re: Defibrillators

Post:
Cool...ok, how about putting an AC source across the heart. WHY do we
die from electrocution...is it simply the I and V that knocks out the
heart or is it that the period of the I interferes so much with the
heart rhythm that we can't recover? I've heard that the death rate from
electrocution is actually higher in the US than Europe because 110 is
closer to the natural heart rhythm than 220. Dunno if that's true. Any
clues?

Chele

On 2/8/2007 9:50 AM, Paul Doherty wrote:
> Hi Chele
>
> Many defibrillators are pulsed DC devices.
> Skin is a resistive conductor, I didn't see it in the data sheets but
> I recall? that defibrillators deliver 600 volts.
> And a 600 volt potential difference can drive current through skin
> resistance.
>
> The current flows through the bulk of the body including the heart.
>
> Current flowing across the internal resustance creates voltage.
> All you need at the heart is to induce -0.1 volt to externally trigger
> the nerves to "fire" which control the heart muscles.
>
> That's why hospitals have to be so careful about using "Hospital
> grounds" during open heart surgery.
> a stray volt here or there can induce nerves in the heart to "fire"
>
> Paul D
>
>
> On Feb 8, 2007, at 6:38 AM, cablem wrote:
>
>> Ok, perhaps I asked the question poorly. I don't want to know how the
>> device works, exactly, I want to know how the current is transported
>> through the body. That's the conductor? What makes the circuit?
>> Obviously, it has to be more than the skin. Or, is it an induction
>> device?
>>
>> Chele
>>
>>
>> On 2/7/2007 8:02 PM, Wallin, Stephen R wrote:
>>> Here's another 4th ventricle
>>> http://en.wikipedia.org/wiki/Fourth_ventricle
>>> complete with its own Purkinje cells
>>> http://en.wikipedia.org/wiki/Purkinje_cell
>>> These cells are neurological pacesetters. Its unproven, but tasers
>>> in some cases could interfere in a
>>> anti-defibrillating way. http://en.wikipedia.org/wiki/Taser
>>>
>>> Stephen
>>>
>>> -----Original Message-----
>>> From: tap-l-owner@lists.ncsu.edu [mailto:tap-l-owner@lists.ncsu.edu] On
>>> Behalf Of Vacek Miglus
>>> Sent: Wednesday, February 07, 2007 2:49 PM
>>> To: tap-l@lists.ncsu.edu; cablem@wfu.edu
>>> Subject: Re: [tap-l] Defibrillators
>>>
>>> cablem wrote:
>>>
>>>> Does anyone know the science behind defibs? Do they work by the
>>>> conduction of electricity between the paddles or do they work by
>>>> induction where the mag field penetrates the skin? I've heard that
>>>>
>>> skin
>>>> is a pretty good insulator...so the first might be possible if the V
>>>>
>>> and
>>>> I are high enough to overcome the resistance. But, the second might
>>>> work, too. Or a combination...
>>>>
>>>> So, how do they work?
>>>>
>>>
>>> Nice write up in Wikipedia:
>>> http://en.wikipedia.org/wiki/Defibrillators
>>>
>>> The quick and dirty: discharge a Capacitor (DC) though the chest to
>>> stop
>>>
>>> the heart from ventricular fibrillation, i.e. twitching uncontrollably.
>>>
>>> Vacek
>>>
>>>
>>>
>>>
>>>
>>>
>>
>> --~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>> Machele Kindle
>> Lab Manager
>> Physics Dept.
>> Wake Forest University
>> Winston-Salem, NC 27109
>>
>> Phone: 336-758-5532
>> Fax: 336-758-6142
>>
>>
>> "Get Fuzzy"
>>
>> Bucky, the arrogant cat: Aaaaaaaa!
>>
>> Rob, the geeky owner: 11:55. Right on time for his nightly freakout.
>>
>> Satchet, the lovable dog: Ever notice how he runs circles in the same
>> direction?
>>
>> Buckey: Yaaaaaaaa!
>>
>> Rob: Maybe the coriolis effect works on cats, too, eh?
>>
>> Satchet: Ha, ha! I have NO idea what that means!
>> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>>
>>
>
>
>
>

--
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Machele Kindle
Lab Manager
Physics Dept.
Wake Forest University
Winston-Salem, NC 27109

Phone: 336-758-5532
Fax: 336-758-6142


"Get Fuzzy"

Bucky, the arrogant cat: Aaaaaaaa!

Rob, the geeky owner: 11:55. Right on time for his nightly freakout.

Satchet, the lovable dog: Ever notice how he runs circles in the same direction?

Buckey: Yaaaaaaaa!

Rob: Maybe the coriolis effect works on cats, too, eh?

Satchet: Ha, ha! I have NO idea what that means!
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~




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