Re: drsstc (Capacitor Lethal charge)

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Peter Terren" <pterren-at-iinet-dot-net.au> 

A couple of weeks ago I defibrillated a patient in recurrent ventricular 
fibrillation 8 times over 90 minutes along with artificial ventilation and 
continuous cardiac massage and he survived (that part at least).  The 
typical shock used is 200J which if unsuccessful is repeated at 200J then 
360J. He would have had a total of 1.6kJ to his chest during that time.
Ventricular fibrillation is incoordinate contraction with no useful 
pumping. The shock clamps down the heart and hopefully it starts again in a 
coordinated manner.
For elective use for less serious heart rhythms, the shock is delivered in 
a synchronous manner to prevent it being delivered during the phase of 
electrical conduction when repolarisation is occurring (the T wave) when 
the heart is vulnerable to being put into VF although if this happens you 
just repeat the shock.
The defib cap does run to 500J but is limited in use and it does have a 
series inductor to limit the peak current.  Burns can occur with multiple 
shocks or poor contacts.  With the very best skin preparation with cleaning 
the oils with alcohol then using conductive jelly and the usual conductive 
pads and firm pressure I have been able to get down to 48ohms from memory 
(the machine prints this out) .
I remember very old information that I grew up with that suggested that an 
electric shock current across the arms of 100 - 200ma was most likely to 
induce VF and be lethal (presumable this was AC) but over this was likely 
to stop the heart (asystole) and it had a better chance of restarting.
I have two defib caps of 38uF 5.2kv for can crushing on my site
http://tesladownunder.iinet-dot-net.au/Other_HV_stuff.htm

Peter
There's nothing like the smell of defibrillation in the morning...

>Original poster: Sparktron01-at-comcast-dot-net David, Bob
>The standard safety "rule of thumb" is any capacitor over 10J stored
>energy is considered lethal.  Voltage definitely enters into mix (a 30V cap
>is certainly less dangerous shock wise then a 3kV one), both can cause
>thermal injuries.  > > Original poster: DRIEBEN-at-midsouth.rr-dot-com

> > Hi Bob,
 > The defibs that I've seen in my profession (firefighter)
 > generally have two energy level shock settings - 200 joules
 > and 360 joules, so I would assume that they are not charged
 > up to their maximum rated voltage for "shocking". Seems
 > strange that an electric charge that would almost certainly
 > be lethal to a normally healthy, conscious person can "shock"
 > a fibrillating heart back into the "normal" electrical ry-
 > thym, thus possibly saving a life. Dosen't it only take a
 > couple of joules to be mortally dangerous?
 >
 > David Rieben
 >
> > > Original poster: "Bob (R.A.) Jones"
> > > > The latest capacitor technology has caps of much smaller
> > > > volume/energy ratios than either of the caps that you mention.
> > > > Difribrillators have a capacitor of appr. 5.2 kV at around
> > > > 35 to 40 uFD rating and they are not much larger than say two
> > > > combined microwave oven filter caps. I suppose their
> > > > peak current rating dosen't have to be that great since
> > > > they're designed to discharge across a relatively high
> > > > resistance - human chest :^O Even with the conductive gel
> > > > that they apply to the skin before shocking, the resistance
>>>> > would still probably be in the dozens, if not hundreds of
> > > > Ohms.
>>>>but what the h$## are they
> > > trying to do to
> > > the patient 540J into his chest!!
> > > Does it double as an elephant defibrillator too !!
> > > Bob