EBME Forums Forums Maintenance Technical Assistance microshock by ionisation in the skin

Hi guys,
I'm trying to find information on microshocks causing ionisation of the skin specifically if this could be caused by placing electrodes using a 5V DC power supply across a simple metal conductivity sensor such as those used on eneuris alarms directly onto patients skin rather than under a bedsheet.
I would be grateful if anyone who has any knowledge could give me their views or experiences please.
Thanks.
Chris

In therapy, DC may also be referred to as galvanic current.

Galvanization also has an electrolytic effect which can cause cauterization of the skin where the cathode electrode comes into direct contact with the skin (see also "electrolysis" and "catholysis"). That is why wet cloth or sponges are generally placed under underneath the cathode (and often under both electrodes in cases where two are used - during electrotherapy in the physio department, for example).

I'm not sure what you're getting at with "microshocks" there, Chris. DC is not a stimulation current in the true sense, as it does not produce stimulation of the cells. In electrotherapy, its value is in altering the ionic state of play by polarization within the tissues. It is only during switch-on (and off) that a short stimulating effect occurs due to an exchange of K (Potassium) and Na (Sodium) ions through the cell(s) membrane.

If you're in "Googling" mode (or mood):- see also the "Sodium Pump"!

With regard to nocturnal enuresis alarms, I believe that modern types have a sensor which clips onto underwear, whereas the older types used to employ a sensor pad. I have never heard of such sensors (electrodes) being directly attached to the skin.

A microshock Geoff is a small electrical shock around 10uA which when applied to the heart can lead to cardiac arrest. Although this current does have to pass through the heart so I'd be surprised if an Enuresis could cause this. (are class CF Enuresis alarms available?)

If you have access to Web of Science or know someone with Athens access there's a lot available on the subject of microshocks, but these are dealing more with the risks from electrosurgical equipment during surgery or indirect shocks from HV use like working on overhead lines.

As we know, the myocardium is most sensitive to alternating current in the range 30 to 100 Hz or so. So currents derived from mains electricity at 50 Hz are usually ideal for inducing fibrillation.

Higher frequencies (ie, electrosurgery - or "surgical diathermy"), DC, and AC which does not pass through the heart do not cause fibrillation but rather heat up and burn the muscle they flow through, sparing skin and fat.

"Microshock" is a term used to describe the induction of ventricular fibrillation by small electrical currents (below the threshold of skin sensation) when applied to very small areas of ventricular muscle, usually by vascular catheters or wires. It requires a small area of contact with heart muscle so that the current density is high despite low current.

When people talk about "microshock" they are generally (but not necessarily - as there are a few sloppy folk about) thinking of alternating currents. And usually stray ones, at that.

However, you could say that all that is a "million miles away" from Nocturnal Enuresis Alarms which invariably (as in, always) operate at low voltage DC.

Can I get away with this broad, sweeping statement?:-

In general DC depolarizes, whilst AC (and/or pulsed DC) stimulates!

While higher frequencies don't cause fibrillation, the paper "A Method to Detect the Microshock Risk During a Surgical Procedure" by Spalding L, Carpes WP, Batistela NJ actually identifies a failure of mains isolation as the potential problem and not the high frequency current.

Yeah, but what do they know?

Of course the voltage (PD) has to come from somewhere ... even the great Georg Ohm realised that!

And (since you added the abstract) ... do we have any idea what it is those guys are trying to sell?

No, after reading it absolutely no idea what so ever Paper started off OK but lost it near the end and doesn't seem to have take off.

With regard to microshock in the skin..

I haven't heard of such a thing but I did some work on DC current many years ago.

Low levels of DC current usually more than 1mA/square inch can cause quite serious ulcer like burns. Geoff explained the effects of Galvanic current earlier.

DC Electrotherapy machines have been tried in the past and discontinued due to the galvanic effect. This effect, if used carefully can have some clinical benefits and I reviewed a device about 10 years that used an AC wave 'floating on a DC level delivering a mixture of high voltage/low current AC stimulation and low voltage (less than 5V) DC. see: https://www.ebme.co.uk/arts/aps/index.htm

Although the term "galvanism" is a bit archaic these days, I'm told that such things as Galvanic Massagers are used in beauty salons (and the like) and can be very effective in revitalizing and cleaning facial skin.

Apparently, ultrasound is used in a similar fashion, and reportedly with good results.

Like TENS, I guess it's a question of "if it works for you, then that's just fine" (and that's all it needs to do).

In similar vein ... how about electro-acupuncture? Has anyone had any success in checking that those things are working properly?

I think there is a lot of merit in using DC current, or pulsed DC (carefully) for therapy, but it needs someone to do some proper research on the most effective ways to utilise it.