Nerve injury after estim

[pwned]

So I have been wanting to ask this because from my last estim experience I took away a permanent pain in my genital area. I assume that some nerves have been injured by the current. I don't understand how it happened though. This condition has not healed completely by itself for several years actually and caused me tremendous misery.
From what I understand from forums like these everything should have been fine though and I totally did not see this coming. Maybe someone has heard of this before and knows how to explain it.
The device I used was a DIY stereo stim device. I got it from a blog somehwere that I cannot find again. The design basically uses a USB soundcard that is opened up and connected to LT700 audio transformers to increase voltage and decrease current. The transformers are used in reverse with the usually output side (low ohm) used as input from the sound card. I did some measurements with a 1kOhm resistor and found it to have maximum output of about 20V/20mA. Usual stimming I did was probably more at 10V/10mA. I usually used conductive rubber loops in various places as electrodes. I also tried to amp up a buttplug with silver foil but it didn't work very well.

So I wonder if anyone can relate to this. Thanks!

The design of the powerbox was this: https://kinkitech.wordpress.com/stereo-stim-usb/

[diglet]

Thank you for sharing your experiences. I've been trying to do research into the safety of stim boxes for a while, but reports like these are hard to come by.

Can you give a bit more details on how this happened? Did you have a normal session and it started to feel weird afterwards? Or was there a sharp change in signal + pain during the session, suggesting equipment failure?

Was your box only powered by USB 5v?

[tsyogini]

Oof, that is so sad to here!
I'm very aware of the risk of injury, but still they sometimes happen.

In my wilder past have suffered extreme fatigue and blood pressure problems for months after a session of bondage/analplay got much much much to wild. Also officially nothing wrong, but life quality was just down the drain. But I did eventually recover.

I'm wishing you all the best, and sincerely hope that you will recover as well, it can take time but the human body has amazing capabilities to repair itself.

[mantrid]

For years I have been preaching that low frequencies can be dangerous because they can cause electrolysis and thus denaturation of molecules. (These frequencies can also be sampling effects or caused by malfunctions such as a ground loop.) That's why I block frequencies less than about 200 Hz using a high-pass filter.

Many teases / estim files use low frequencies because they seem to feel different ... (Due to the high-pass filter I recognize such files by feeling nothing.)

AFAIR I even found a publication a few years ago which listed safe currents at certain frequencies for medical purposes. Unfortunately I did not bookmarked it.

Some care should also be taken when placing electrodes at non-sensitive positions, because very high (maybe to high) currents are needed to feel something.

[picofarad]

That's why I block frequencies less than about 200 Hz using a high-pass filter.

I've thought about adding a high-pass filter but not sure where to place and how to size the (capacitator). I have a commercial audio amp (Fosi BT20a Pro) where I feed it into two transformers. I do have a pair of 4 ohm resistors in series between the audio amp and the transformers.
If you could let me know what you did or point me in the right direction that would be much appreciated!
Thanks!

[diglet]

@mantrid

The best source I know on estim safety is this paper: Electrical stimulation of excitable tissue: design of efficacious and safe protocols.

For low frequency signals, you are looking at figure 8. The safe limits are defined by the charge-per-pulse and the electrode area. The rationale is, I believe, that the skin can only tolerate so much charge imbalance before negative effects occur. They use the square root of the electrode area, but really the circumference matters because most of the charge density is at the edges of the electrode. They say damage is caused by:

The mechanisms for stimulation induced tissue damage
are not well understood. Two major classes of mechanisms
have been proposed. The first is that tissue damage is caused
by intrinsic biological processes as excitable tissue is over-
stimulated. This is called the mass action theory, and pro-
poses that damage occurs from the induced hyperactivity
of many neurons firing, or neurons firing for an extended
period of time, thus changing the local environment. Pro-
posed mass action mechanisms include depletion of oxygen
or glucose, or changes in ionic concentrations both intra-
cellularly and extracellularly, e.g. an increase in extracellu-
lar potassium. In the CNS, excessive release of excitatory
neurotransmitters such as glutamate may cause excitotoxic-
ity. The second proposed mechanism for tissue damage is
the creation of toxic electrochemical reaction products at
the electrode surface during cathodic stimulation at a rate
greater than that which can be tolerated by the physiological
system.

Depending on how you calculate it exactly, I found lower safety limits of 500-2000hz. That is to say, "unsafe low frequencies" are not very low frequency especially if you stick your electrodes in not so sensitive spots.

There are more damage mechanisms than just this one, but the other mechanisms are not particularly likely at low frequencies or are very easy to identify (thermal burns).

[darthjj]

Thank you for sharing your experiences. I've been trying to do research into the safety of stim boxes for a while, but reports like these are hard to come by.

That would be great! Too many times estim safety discussions have been met with some variation of "it's 100% safe because I haven't heard of people getting any adverse effects from it". I don't think most people understand the amount of data you need to perform a medical study to find something that might happen over a long time span.

Well, if you're collecting data, here's a little more for you :)

Current age: 42
Started: 2019
Frequency: On average 1-2 times per month.
Session lengths: 1-4 hours, but rarely up to 6 hours.
Session intensity: Not too extreme, but some BDSM and a few forced orgasms.
Electrodes: DIY, used aluminium and other hardware store metals in the beginning. Now the frequently used ones are nickel-free gold plate for prostate, saline soaked cloth around the balls, and stainless steel for the head 'trode.

Health changes: (disclaimer: I'm not saying any of this is caused by stimming, in fact I'm pretty sure some of my health issues are caused by other things such as simply getting older, but I'm listing them all for completeness sake.) It's got more difficult to get and maintain an erection while stimming, even if it feels nice and/or if jacking up the power. My memory, both short and long term, has got significantly worse. Started getting nosebleeds every now and then, after never having had that since I was a kid. I got tinnitus out of nowhere.

The only health effect I _know_ is stim related is that sometimes my cock feels tingly afterwards, as if the power is still on. After some particularly intense sessions it continued for 24 hours, but nothing permanent.

[mantrid]

I've thought about adding a high-pass filter but not sure where to place and how to size the (capacitator). I have a commercial audio amp (Fosi BT20a Pro) where I feed it into two transformers. I do have a pair of 4 ohm resistors in series between the audio amp and the transformers.
If you could let me know what you did or point me in the right direction that would be much appreciated!

There is a spreadsheet attached to this old posting where you can enter and calculate values for resistors, capacitors, etc.

The best source I know on estim safety is this paper: Electrical stimulation of excitable tissue: design of efficacious and safe protocols.

For low frequency signals, you are looking at figure 8. The safe limits are defined by the charge-per-pulse and the electrode area

Thanks for the source. I have to study it and its references in detail when I have more time. (At first glance this looks a bit strange: They correctly address issues of waveforms with DC components, but the limit given by equation (5.1) does not depend on this. With waveform (a) of Figure 9, unlimited currents (DC component) would be possible just by increasing the pulse frequency ...)

Edit: Fixed the equation number

[diglet]

Some things I learned recently:


I used to have regular skin irritation at the location of one of my rubber electrodes after each session, usually lasting 24-48h. Since building the FOC-Stim, I felt it was reduced slightly but still present. Recently, I switched from 800hz waveforms to 1300hz waveforms. After multiple sessions I can conclude that this has definitely reduced the level of skin irritation even further.

I asked on discord and a few people mentioned not having skin irritation with pulse-based boxes, but skin irritation with the 2B seems more common. One person suggested this might be due to a DC bias in my waveforms. I tried multiple measurement setups and found DC bias to be below the minimum value I could measure, < 0.5µA, absolutely negligible.

Given these results, my only remaining hypothesis is that the irritation is caused by electrochemical effects from waveforms with a too high charge-per-pulse relative to area. Literature says signals with k=1.85 can result in permanent nerve damage. In recent sessions I found k=1.4 with 800hz waveforms and k=1.1 with 1300hz waveforms. The reason the k value is lower for higher frequency waveforms is that less charge is needed to produce the same amount of nerve activation if the pulse is smaller. Calculations for k can be found in the paper linked a few pages back or on the restim wiki.


Second, there was one user report on discord which I found interesting. The user was stimming with a welded stainless steel chastity cage and reported a burning sensation after session. User stated he has not experienced this with CR or other stainless steel rings. This suggests that a burning (as opposed to itchy) sensation is an indicator of poor quality metals.

Thanks for the source. I have to study it and its references in detail when I have more time. (At first glance this looks a bit strange: They correctly address issues of waveforms with DC components, but the limit given by equation (5.1) does not depend on this. With waveform (a) of Figure 9, unlimited currents (DC component) would be possible just by increasing the pulse frequency ...)

The equation is based on balanced waveforms. They cite like 6 studies showing the damage thresholds for monophasic stimulation are much lower than for biphasic stimulation:

These studies showed that monophasic
stimulation causes significantly greater tissue damage than
a non-stimulated implant at 1 µC/mm2 per pulse but not
0.2 µC/mm2 per pulse, and that charge-balanced biphasic
stimulation does not cause significant tissue damage at lev-
els up to 2 µC/mm2 per pulse.

and

Scheiner found that cat muscle tis-
sue was significantly damaged using monophasic stimu-
lation at 0.4 µC/mm2 per phase, and that when charge-
imbalanced biphasic stimulation was used, tissue was dam-
aged with 1.2 µC/mm2 per phase cathodic and 0.2 µC/mm2
per phase anodic, and could safely tolerate 1.2 µC/mm2 per
phase cathodic and 0.5 µC/mm2 per phase anodic. No elec-
trode corrosion was observed under any of the conditions
studied.

(and more)

[mantrid]

I used to have regular skin irritation at the location of one of my rubber electrodes

It may be caused by short carbon fibers from conductive rubber.

I asked on discord and a few people mentioned not having skin irritation with pulse-based boxes, but skin irritation with the 2B seems more common. One person suggested this might be due to a DC bias in my waveforms. I tried multiple measurement setups and found DC bias to be below the minimum value I could measure, < 0.5µA, absolutely negligible.

Given these results, my only remaining hypothesis is that the irritation is caused by electrochemical effects from waveforms with a too high charge-per-pulse relative to area. Literature says signals with k=1.85 can result in permanent nerve damage. In recent sessions I found k=1.4 with 800hz waveforms and k=1.1 with 1300hz waveforms. The reason the k value is lower for higher frequency waveforms is that less charge is needed to produce the same amount of nerve activation if the pulse is smaller. Calculations for k can be found in the paper linked a few pages back or on the restim wiki.

Electrochemical effects are reverted up to a certain degree if the polarity is changed. This, of course, does not work is you change the polarity after half a year, i.e. it is frequency dependent. I can imagine that low frequencies (not just DC current) can indeed cause such issues.

Second, there was one user report on discord which I found interesting. The user was stimming with a welded stainless steel chastity cage and reported a burning sensation after session. User stated he has not experienced this with CR or other stainless steel rings. This suggests that a burning (as opposed to itchy) sensation is an indicator of poor quality metals.

Another possible problem is bad contact resistance, i.e. spots with high current densities. That is something one should feel und I would expect it with non-flexible electrodes.

The equation is based on balanced waveforms. They cite like 6 studies showing the damage thresholds for monophasic stimulation are much lower than for biphasic stimulation:

Indeed, equation (5.1) only makes sense for a given waveform. If DC-component is zero, this equation implies a frequency dependence: For a given electrode size (and waveform) maximum current is proportional to the frequency.

AFAIU, they tested with only a single frequency (on a cat brain ) and assumed the mentioned frequency dependency, which lead to the charge limit.

[darthjj]

I used to have regular skin irritation at the location of one of my rubber electrodes after each session, usually lasting 24-48h.

Do you know if that electrode has CR has a nickel based conductive filler? I've noticed most estim vendors don't disclose if their CR contains nickel or only carbon. If only one of your CR electrodes causes this, I guess you could measure if it's more conductive than your other CR electrodes. AFAIK nickel based CR is about 10 times more conductive than pure carbon based.

As a bonus, while trying to find numbers for CR I stumbled upon a rubber molding company which (accidentally I assume) used a photo of an e-stim product: https://zetarmoulding.com/what-are-the- ... mulations/ section 4

[diglet]

I used to have regular skin irritation at the location of one of my rubber electrodes after each session, usually lasting 24-48h.

Do you know if that electrode has CR has a nickel based conductive filler? I've noticed most estim vendors don't disclose if their CR contains nickel or only carbon. If only one of your CR electrodes causes this, I guess you could measure if it's more conductive than your other CR electrodes. AFAIK nickel based CR is about 10 times more conductive than pure carbon based.

I don't know. It is flat omega rubber from Joanne's shop.

I suspect it is carbon, it measures about 50ohm DC with the multimeter probes very close together. I have to occasionally sand it to restore the resistance.

[darthjj]

I don't know. It is flat omega rubber from Joanne's shop.

I suspect it is carbon, it measures about 50ohm DC with the multimeter probes very close together. I have to occasionally sand it to restore the resistance.

Yea, that sounds on par with the numbers I've seen from carbon CR. Though I assume it's originally made for EMI shielding or something, and not designed extended skin contact, so perhaps it could have some additive or contaminant that irritates the skin. Or it's the thing mantrid suggested, I've seen some DIY conductive rubber using CF but other than that and in scientific papers, I got the impression that CR usually uses carbon black rather than fiber. But that's just what I remember from searching for CR offered in stores, could be wrong.