Talk:Electrosurgery/Archive 1

Archive 1

How monopolar therapy works

There has been some alteration to this article by somebody who thinks that the spark originating from the monopolar electrode is dependent on a spark gap or interuption of flow in an inductor. In fact, it is not. A modern electrosurgical unit is not a Ford Model A spark coil with a chatterbox. It's a high frequency AC voltage, not dependent on interuption of anything. If the monopolar tip is touched to the skin, destruction will continue at the skin surface, and below it. All that happens when the probe is raised, is that the current entry is spread over a larger skin surface area, so more skin burning and external superficial carbonization (visible charing occurs). Otherwise the process is exactly the same-- it simply happens at a different (more superficial) spot. Yes, a longer spark can be drawn if the probe tip is touched first to the skin, but that is simply to start the ionization of air and has nothing to do with current interuption. The mechanism for all this is the capacitance of the room at very high frequencies, and the even larger capacitance of the body. This allows current to flow even when the circuit is not complete. But exactly the same process can be seen (with less damage) in a higher voltage Tesla coil, which can be seen throwing sparks of current freely into the air at the tip, even with nothing to contact. If fingers are brought near, these sparks can be attracted, and even made longer. But there is no circuit interrupter and the spark gap remains throughout this process and does not ever need to be zero. This proves quite well that it's not necessary to ever close it. The gap and the spark's visible presense across it serves only to make the effect visible, and to make the skin damage (when it occurs) more superficial SBHarris 23:23, 2 June 2007 (UTC)

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REPLY: If it is just a capacitance effect, why is there a spark? There are no such sparks in capacitors nor when I use capacitive "touch" sensors that are sometimes found in elevators or on microwave ovens, etc. Yes, the return path from the patient to the ground reference of the electrosurgical unit is capacitive when no return plate is used (more on this later), but the spark gap has nothing to do with capacitance of the air. It has to do with the dielectric breakdown strength of air which is a function of the energy required to strip the outermost electron from air molecules (mostly N2 and O2, but also dependent on ions and contaminents in the air). Moreover, the spark gap mode can be used with a return plate in place, in which case the current path is completely that of Ohmic currents, and capacitance places absolutely no role in the operation.

To cause a spark requires the breakdown (i.e. ionization) of the air, which requires an E-field of 3x10^6 V/m or 30,000 V/cm or 3,000 V/mm. This parameter is independent of frequency. Once the spark has started, the air in the gap becomes a conductor, i.e. a plasma with very good conductance. The current is not a displacement current, but a real, Ohmic current with actual electrons traversing the length of the spark. The electrons of this plasma conductor are exactly those electrons that have been stripped from the air molecules.

"A modern electrosurgical unit is not a Ford Model A spark coil with a chatterbox. It's a high frequency AC voltage, not dependent on interuption of anything." When operating in non-fulgurate mode, this statement is certainly true: output is a moderately large AC wave (ballpark of 50V and 1MHz). When in fulgurate mode, the situation is quite different and the modern electrosurgical unit is acting the same as a spark coil. To get the 30,000 V/cm field strength necessary to break down the air, you need one of two things to happen: get the probe to within 16 micrometers of the skin (3e6V/m / 50V) or you need to touch the skin and then break contact to get the voltage on the output inductor to climb exponentially until the air breaksdown. The latter is exactly what happens in a spark coil.

Because it is based on the spark coil effect, the spark gap is actually continually dying out and then being regenerated. (When the AC voltage of the generator hits a zero crossings the spark gap will often die out termporarily.) This effect causes a noisy high-frequency output, higher than the 1MHz sinewave output. It is this aspect of the spark gap effect that makes it much easier to use the fulgurate mode without a return plate; i.e. the impedance for the capcitive return path is smaller for higher frequencies, Zc=1/(2*pi*j*f*C), and the spark gap causes a lot of higher-frequency content, as compared with the normal mode of operation. This effect is what happens in spark coils, Helmholtz coils, and Telsa coils.

Lastly, keep in mind that the energy that is harnessed in such procedures is simply Ohmic heating from an Ohmic current. At 1 Mhz, we are not talking about radio wave propogation, which is a common misconception with electrosurgery. For this to be radio propagation, we would need to be in the far field, which is about 150 m or so.

SUMMARY:

• A spark is produced when the electric field in air exceeds 3,000V/mm. Neither capacitance nor frequency play any role in this.

• The output inductance of the electrosurgical unit, and its reactive nature of producing an exponentially growing voltage when current is interrupted, is crucial to reliable operation of spark gap mode.

• The capacitance of air has nothing to do with the generation of the spark. The capacitance only plays a role when a return plate is not used, in which cases the current returns from the patient to the electrosurgical unit via the capacitance.

• The spark is absolutely necessary for the higher frequencies (i.e frequencies above the ~1MHz generator frequency) to be present. The higher frequencies allow for the return plate to be omitted from the circuit.

If you don't believe me, attach a current probe around your monopolar probe and capture the waveforms with a scope in the two cases:

1) in normal monopolar mode 2) in spark gap mode.

The current in the second case will not be sinusoidal and will have high frequency noise-like characteristics. Also monitor the voltage waveform in both cases.

Better yet, try producing a reliable, lasting spark with a unit that does not have an output transformer. (Certainly do not try this on a human subject. All spark generators are danegrous and I take no resposibility for injuries.)

Repliedthemockturtle 20:13, 3 June 2007 (UTC)

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A few more clarifications:

You state

• "that is simply to start the ionization of air and has nothing to do with current interuption. The mechanism for all this is the capacitance of the room at very high frequencies, and the even larger capacitance of the body. This allows current to flow even when the circuit is not complete."

First off, the capacitance of the room does not change with frequency and has no direct bearing on the spark. Secondly, capacitance has nothing to do with spark generation. High E-fields cause spark generation. Further, once the spark is generated, the spark shorts out the capacitive path, making the capacitance a moot point.

• "a higher voltage Tesla coil, which can be seen throwing sparks of current freely into the air at the tip, even with nothing to contact. If fingers are brought near, these sparks can be attracted, and even made longer. But there is no circuit interrupter and the spark gap remains throughout this process and does not ever need to be zero."

Not true, the whole Tesla coil process works because an extremely large voltage (and thus E-field) is generated using the inductance of coils. Again this has nothing to do with the capacitance. Moreover, the spark that you talk about in a Tesla coil is the secondary spark. What iniates the large voltage is the abrupt current change that occurs when the primary spark gap changes state from conducting to non-conducting or vice-versa.

The upshot of all this is that a transient current is used to generate a high voltage via the relation

${\frac {dV}{dt}}=L{\frac {dI}{dt}}$

and it is this high voltage which creates the extremely large E-field needed to break down air and generate a spark.

This is how all spark devices operate. It is also how all (inductor/transformer based) DC-DC converters work when the DC voltage is being raised in value (e.g. flyback and boost topolgy power supplies).

I all comes down to

${\frac {dV}{dt}}=L{\frac {dI}{dt}}$

Repliedthemockturtle 22:43, 3 June 2007 (UTC)

• As noted below, it is NOT how all spark devices operate--- just most of them. And all of the lighter ones. The old (or modern and heavy) neon transformers produced a heavy spark, however, on normal 60 Hz current, without interruption. And were noiseless, except for the spark noise. They were just regular transformers. It's autotransformers (single inductors) which need your equation above. Yes, most Telsa coils use various spark interruption devices to boost voltage, but there are many Tesla coil designs, and a perfectly useable one uses a neon sign tranformer to energize a suitable primary, and a cardboard tube with many fine wire turns for the secondary, to get the voltage up to 200,000 V at 60 Hz. These work perfectly well to produce long spark effects, without any spark gap interruptors at all. Though not recommended as a design, due to the danger working with the old (relatively) high-current low-frequency neon sign transformers. SBHarris 00:28, 4 June 2007 (UTC)

REBUTTAL

If it is just a capacitance effect, why is there a spark? There are no such sparks in capacitors nor when I use capacitive "touch" sensors that are sometimes found in elevators or on microwave ovens, etc.

Of course it's not "just" a capacitative effect, and I don't think I said it was. I certainly didn't mean to imply that it was. A spark is a high voltage effect, period, as you point out. In general I have no argument with your physics, although your understanding of how medical Hyfrecators work, is off.

Yes, the return path from the patient to the ground reference of the electrosurgical unit is capacitive when no return plate is used (more on this later), but the spark gap has nothing to do with capacitance of the air.

Read what I said. It's the capacitance of the room and (even more) the capacitance of the body WRT the room and which is absorbing the current of the spark (then discharging it). It's of course the capacitance of the entire system of room plus patient plus machine, but the patient serves the same function as the insulated ball in an electrostatics experiment. Talking about a "capacitative return path" or even about "displacement current" (as a previous author did) is misuse of language, and should be discouraged because it implies a physical process which actually does not happen. Diplacement current was never a good term. There is no return path because there is no return current by any good definition of the word current (movement of charges = current; no moment = no current). A "displacement current" is an oxymoron, since it involves no movement of charge, either-- at least in the capacitor dielectric gap, where it is said to exist.

I agree with the physics of air breakdown in your next paragraph and the fact that when a ground plate is used there is no "displacement current." or capacitative "return." However, when there is no plate, the current is "ohmic" only in the spark, and the "return" current is actually non-existant (ie, it is of the displacement type, which means it's not real) and consists only of an increasing electric field as charge is dumped one way onto a chargable capacitor. Yes, it's just plain current and radio waves are mostly not involved (even though it's RF frequency).

When in fulgurate mode, the situation is quite different and the modern electrosurgical unit is acting the same as a spark coil. To get the 30,000 V/cm field strength necessary to break down the air, you need one of two things to happen: get the probe to within 16 micrometers of the skin (3e6V/m / 50V) or you need to touch the skin and then break contact to get the voltage on the output inductor to climb exponentially until the air breaksdown. The latter is exactly what happens in a spark coil.

Question: what in the world makes you think that the voltage in a modern fulgeration device like a Hyfrecator (one of which I own and use) is anything like 50 V, the figure you use above? A modern device puts out anything from 3,000 to 8,000 volts at 20 watts [1], and does this (produces the voltage) whether in contact with skin or whether producing a spark (of course the current isn't the same when the device is simply triggered in air). At 3,000 volts you get air breakdown and spark at 1 mm from the skin, and at 8,000 V it's about 3 mm. You can see quite clearly that you can start a spark (try with your own device if you doubt) without ever touching the skin (and yes, after you do, you can lengthen the distance due to the plasma bridge you describe). Thus, the interuption mechanism of the "points" in an old automobile is NOT used at the skin, and does NOT need to be used at the skin! So get over it, and don't put it in the article!

Now, at this point, I'm going to admit an error and partly retract something I said above. It certainly IS possible to generate large uninterupted sparks with smooth AC voltage alone. In fact, I used to have a 10 lb neon sign transformer which ran on simple 60 Hz and powered a very long spark up a Jacob's ladder, with no point contact ever needing to be used. Nor was it an interupted high frequency supply-- just a 15,000 V plain old iron core 60 Hz transformer (and a damned dangerous one, at that). But if you want to go light-weight, you need to use autotransformers (single inductors, much like auto ignition coils) with high frequency (or short pulse) switching into them to get the high change in current needed, and for that you need a charging waveform which has some high frequency components, indeed. That is my error. My Hyfrecator is a lot lighter than my neon-sign transformer, and it produces a whine and a noisy spark (as you say) which is very suggestive of interrupted DC switching which I assume it indeed has (though I have no scope at the moment to see directly). However, this is not created with some kind of air gap switch, either at the patient's skin or inside the device. It produes the same whine, whether you have an air-gap or not. The hiss of the spark (which you near only when there is a spark) is also irrelevant, because the spark does not need to exist, for the machine to run and burn tissue (i.e., if you have no plate yet make tissue contact with the probe only, so there is no spark). Finally, the machine itself has no moving parts, and neither do today's lightweight sign transformers. Rather, the switching is done electronically at low voltage, as in our modern Direct Ignition automobile systems which have no contact points. Then, this low voltage switched-current goes into an autotransformer (some kind of "coil"), end of story. So yes, the system is like an auto spark-coil/ignition coil inasmuch as there's a spark coil autotransformer, like the one (or more) in any gasoline automobile, and the waveform into it is not a sine wave. But (again) the airgap at the patient plays NO role in how this voltage is created, since the machine can be used in a mode where no spark exists, when burning the deep parts of a wart, or some other deep structure where the device point is held in contact with the patient's skin to obtain destruction of deeper subcutaneous tissues, with minimal external skin damage.

SUMMARY: A spark is produced when the electric field in air exceeds 3,000V/mm. Neither capacitance nor frequency play any role in this.

Except as the high frequency waveform components necessary to get high voltages out of autotransformer/induction coils/spark coils.

The output inductance of the electrosurgical unit, and its reactive nature of producing an exponentially growing voltage when current is interrupted, is crucial to reliable operation of spark gap mode.

That is quite wrong, as explained above. Interruption of low voltage current is done electronically inside the machine, just as in your 21st century gasoline automobile ignition system. The system works fine with NO airgap or spark at the patient, just differently (i.e., different deeper structures are destroyed in tissue).

The capacitance of air has nothing to do with the generation of the spark. The capacitance only plays a role when a return plate is not used, in which cases the current returns from the patient to the electrosurgical unit via the capacitance.

True, with the caveat that there really is no current (charge movement) "return" to the unit, in this mode.

The spark is absolutely necessary for the higher frequencies (i.e frequencies above the ~1MHz generator frequency) to be present. The higher frequencies allow for the return plate to be omitted from the circuit.

Not quite. The high fequences are necesssary for the omision of the return plate, because they allow the high AC currents with no return lead, as a capacitative dump. The spark, however, is completely superfluous, as noted above. Tissue is destroyed just fine without it, return plate/wire, or none.

If you don't believe me, attach a current probe around your monopolar probe and capture the waveforms with a scope in the two cases: 1) in normal monopolar mode 2) in spark gap mode. The current in the second case will not be sinusoidal and will have high frequency noise-like characteristics. Also monitor the voltage waveform in both cases.

This may be true, as noted above, but it doesn't make your point about the spark. Or what is happenning in the spark. The spark (once again) does not need to exist for the voltage or the tissue destruction to occur, even in "non-return" monopolar mode with no ground plate. If you don't believe ME, take your Hyfrecator with no ground-plate or return circuit, touch it to some part of your skin overlying a bit of tissue you don't need (I suggest a deltoid), and turn it on, by pressing the foot plate (or have somebody else turn it on). Be careful to push the probe hard to the skin, so as not to let a spark form, and thus the mechanism you describe cannot possibly operate to produce high voltage. Remember to say "ouch!". And yes, you can quit this anytime you're willing to admit that I’m right and you're wrong, on this point about how the high voltage is produced. The longer you wait, though, the deeper and bigger your interior burn beneath the skin will be. If you watch carefully in a dark room, you may see some interior sparking under the skin, but that's not due to any current interruption at the skin. It's just the same glow you get from a pickle being fried by high temperatures of a (relatively low votage) electric current from your main. SBHarris 00:07, 4 June 2007 (UTC)

REBUTTAL TO REBUTTAL

• What makes me think that an electrosurgical unit puts out 50V instead of several kV?? I've taken part in the design of such units by a manufacturer of such devices. I have 17 years experience as an EE. Two degrees in electrical engineering and a PhD in Plasma Physics. I have written a book on electromganetics. I designed microwave circuits, analog test equipment, etc. I have published in trade journals and academic jounals. I know a little on the topic.

• • I believe you. The topic is electrosurgery and you know a little about it. But that can be fixed! We're all ignorant about most things, after all. I, for instance, know little about plasma physics. If you want to know about modern electrosurgery machine characteristics, start here with characteristics of a number of units on the market: [2]. FYI, cutting voltages in none of these devices are as low as 50 volts, but on average at least several hundred volts (usually more than a couple of hundred), and coagulation voltages (lower duty cycle but higher peak V) are almost always over 1000 volts, typically a few kV. "Spray coagulation" voltage, which is what they call fulguration in the O.R. setting at medium and high power (and with a return electrode always) goes up to 9,000 volts in these devices. The most common no-return lead device for fulgeration, the Hyfrecator (a brandname) goes from 3,000 to 8,000 volts, depending on setting. I gave you the reference for that: the figures are on page 8. [3] I'm curious as to what units you took part in the design of? Made by what company? I do not know of any marketed electrosurgial devices which work at a voltage as low as 50 V, and I've done a fair amount of searching. But it's hard to prove a negative, so since you're the claimant, I'd be interested in a specific reference to a specific device. In any case, that voltage is far from standard for these devices for any purpose, and my references for that fact, are given above. SBHarris 05:10, 4 June 2007 (UTC)

• You say

Talking about a "capacitative return path" or even about "displacement current" (as a previous author did) is misuse of language, and should be discouraged because it implies a physical process which actually does not happen. Diplacement current was never a good term. There is no return path because there is no return current by any good definition of the word current (movement of charges = current; no moment = no current). A "displacement current" is an oxymoron, since it involves no movement of charge, either-- at least in the capacitor dielectric gap, where it is said to exist.

Of course there is a return path. Displacement current is a perfectly well defined term. You just treat the changing electric field as the current. In the Fourier domain, this is the imaginary component of (conductance/dielectric constant times the electric field). No ambiguity. The current through capacitors and inductors is used all the time. When the return plate is omitted, the capacitance that is important here is the capacitance directly between the subject and the return of the unit (and to a lesser extent "two node" paths such as subject to table to unit etc but capacitances in series add by the 1/(1/C1+1/C2) rule). It is via this capacitance that the circuit is closed.

By this definition, no circuit can be fully open. Which is what makes it a bad definition. So I suggest a better one. SBHarris 05:56, 4 June 2007 (UTC)

Rather, the switching is done electronically at low voltage, as in our modern Direct Ignition automobile systems which have no contact points. Then, this low voltage switched-current goes into an autotransformer (some kind of "coil"), end of story. So yes, the system is like an auto spark-coil/ignition coil inasmuch as there's a spark coil autotransformer, like the one (or more) in any gasoline automobile, and the waveform into it is not a sine wave.

I really am not clear as to what you are saying. It doesn't matter whether you use a spark gap or solid state devices, you need to generate a very high voltage from a very low DC voltage, and to do this you need to switch the current in an inductive device in an abrupt manner

${\frac {dV}{dt}}=L{\frac {dI}{dt}}$

That is all I am trying to say. It has nothing to do with capacitance.

As noted, I never said it did. I used "this" in a sentence ("the mechanism for this"), which referred back to something previous (a spark with an open ciruit) which you assumed was something else. Just goes to show that if writing can be misunderstood, it will be, and I should have writen it more clearly.

• You say "A modern device puts out anything from 3,000 to 8,000 volts at 20 watts"

I have never used the Hyfrecator. It may very well have a special mode that puts out a high-voltage low current waveform. The unit that I am familiar with (made by one of the manufacturers listed on the wiki) puts out a (nominal) 50V AC 1MHZ in all modes. This is a fact. It relies upon the spark gap method for fulguration mode.

Reference, please? I gave you mine. In 15 units on the market, none go as low as 50 V, and common coag voltages are 1-3 kV. If there was a 50 V device it would obviously have to depend on something other than voltage to get a spark for anything, but most devices use far higher voltages for everything they do, particularly fulgeration and coagulation. I don't believe any device relies on the "spark gap method" to help in switching the spark current, since all devices I'm familiar with produce the same voltage on fulgeration mode whether or not a spark is produced (ie, fulgeration is actually being done). Testing of electrosurgical devices requires high voltage test equipment, for this reason [4] But feel free to provide a cite for the device you reference. I did for the Hyfrecator.

I looked in your link ([5]) and I do not see any data on the output in fulguration mode (3,000 to 8,000 volts at 20 watts). I don't have a manual for this device, so I cannot confirm or deny this data.

See page 8 of 12.SBHarris 06:11, 4 June 2007 (UTC)

With what you say about the whining (which I assume is like the whine in a camera with flash), then it probably does have a special internal circuit that generates a high voltage in fulgurate mode.

Unlikely, since the voltage range is from 3 kV to 8 kV. However, lower voltages may well be used in coag mode. This unit is not designed for cutting, so it probably has higher than average voltage ranges.SBHarris 06:11, 4 June 2007 (UTC)

I am very doubtful that it produces more than 50 V to 100 V at ~1MHz when in non-fulgurate mode. Please measure this on your unit (into a 50 to 1000 ohm) load before you flame me anymore.

See above. I cannot find an electrosurgical device which produces 50 to 100 V in any mode for any purpose, and I've referenced you specs for 15 of them. So it's your turn.

• You say

"So get over it, and don't put it in the article!" "Be careful to push the probe hard to the skin so as not to let a spark form. Remember to say "ouch!", and yes, you can quit this anytime you're willing to admit that I’m right and you're wrong, on this point. The longer you wait, though, the deeper and bigger your interior burn benieth the skin will be"

I would like to have a reasonable adult conversation here. Please refrain dragging this discussion into insults.

That's just my way of suggesting that experience trumps theoretical knowledge. I have a fulgerator designed for work without a ground, and two surgical devices as well (both have ground fault circuitry and of course cannot be used without a ground). But I've done a lot of fulgeration with these things and I know a spark isn't necessary or needed in this function (or rather, mode). You need an air spark to do fulgeration by definition, but the device will still burn tissue quite effectively in fulgeration mode, if an after contact is made. So the spark is not necessary for the voltage power produced in this mode. Obviously, you haven't had this experience, or you'd know this also. Thus, I suggest you acquire it, by any means you can. SBHarris 05:56, 4 June 2007 (UTC)

• Maybe we can come to some sort of agreement here without it getting personal.

My points are these:

- for fulguration mode, you need a high-voltage signal (kV), whereas in non-fulguration modes lower voltage sine wave (50V to 100V) is used. Again please verify the veracity of this with your unit.

• I'll check it, but with a Hyfrecator, I'm not going to get anything less than 3 kV, as they aren't sold for cutting. I'll be interested to see what the cut voltage is for my human surgical and vetrinary surgical machines. SBHarris 05:58, 4 June 2007 (UTC)

- to produce said high-voltages, you need a switched current through an inductive device

${\frac {dV}{dt}}=L{\frac {dI}{dt}}$

(yes you can do "brute force" tranformer methods as you mention, but this is rarely ever done anymore and it doesn't get you high ferquency content unless somewhere you have a spark gap.)

The high frequency is to keep you from being electrocuted at these powers and currents. The spark is totally irrelevant, and the said voltages and frequencies appear without it. The waveform which produces high dI/dt is necessary to produce such voltages with a single inductor/autotransformer, but again, the waveform is not the spark, and is not produced by the spark, but by the internal circuitry of the device. Any high frequency AC (in the MHz range) gives plenty high enough dI/dt to be put through an autotransformer to give high voltages without out need of a big heavy magnet core (at 1 MHz you can use light ferrite cores). SBHarris 05:58, 4 June 2007 (UTC)

- The transient current in the spark and/or high-voltage circuit are what cause the higher frequency content.

Other way around. The high frequency signal, complete with cuts which take out some sine waves, are what produce high voltage when run through coils. But the even higher frequencies which result are just due to taking out some sine waves in a train via solid state circuitry, and the Fourier equivalent of THAT in pure sine waves (which will naturally have very much higher harmonics). In any case, with the "and/or" you put in, you've gotten yourself away from needing a spark, so that's fine--- But then you don't have your original argument. You don't get a nice 1 MHz output with a simple spark, and the duty cycle controller which moves you from cut to coag (or any blend of them in today's modern machines) is not produced by a spark, but by the circuitry of the device (again). I'm not talking about cut-off sine waves due to a cut-off by conduction, but rather one perfect sine wave followed by a gap, and then another sine wave, which is what modern electrosurgery devices produce on "coag". These things are going to have oscillators and high power thyristors. This circuitry produces high frequency A.C. long before it sees the final output inductor/autotransformer. In my vet unit the Vetroson V-10 [6] I can even get a fully rectified high voltage D.C. output after that, so it's obiously been first put through a transformer, and THEN a high voltage diode. And for cutting, I can add a high voltage D.C. component, by choosing a partly filtered version of the high voltage recified D.C., so obviously a (small) capacitor in parallel gets added. And so on. SBHarris 05:58, 4 June 2007 (UTC)

- you can fulgurate with a piece of steak and a return plate. there is no capacitance involved in this case. capacitance is not needed for fulguration.

Nor did I say it was (that was my less-than-clear writing). But a spark is needed for fulgeration only by the definition of fulgeration, not because any physical spark is needed for the machine to produce "fulgeration" voltages and currents in fulgeration mode. SBHarris 05:56, 4 June 2007 (UTC)

Repliedthemockturtle 01:03, 4 June 2007 (UTC)

Steve, I sent you an email. Sounds like the unit that I am familiar with is not typical. AC output is about 150V. As I wrote in the email I'll leave it to you to describe fulgurate as you see fit in article so we don't end up in a pissing contest. I suggest the following though:

1) that you put the paragraph "In fulgeration mode..." before the paragraph "At low-power, this technqiue requires no return..." which would make it more clear that the "no return" aspect of fugulartion but doesn't define fulguration. 2) add some comment (in the "In fulgeration mode...") about the E-field necessary to breakdown air and generate a spark. 3) comment that non-linearities and intermitant nature of spark converts considerable portion of sinewave energy to high frequencies.

It's been a useful discussion for me. I've learned a few things.

Repliedthemockturtle 19:22, 8 June 2007 (UTC)

the long derivation of how electrosurgery works

While of interest to freshman physics students, it's not really helpful here nor very interesting to a biophysicist, since it spends so much time on the elementary derivation without getting to the basic point: passing voltage through a resistor releases heat which raises the temperature very quickly the more concentrated that voltage application is. In fact, we don't need to deal with all that current density nonsense, and it may be worthwhile explaining how AC works better at this than DC (like with Edison electrocuting an elephant), but you can honestly cut all equations except V=IR at dT/dt=P/cm. SamuelRiv (talk) 07:16, 22 April 2010 (UTC)

I assume you refer to the content that was deleted in this edit [7]. I have no objection to its removal. Mikael Häggström (talk) 17:10, 1 September 2015 (UTC)

Possible Typo

I think the following text in the article is an error: 'to which is in turn proportional'

(Please remove this entry once the issue has been addressed.) 213.8.72.181 (talk) 11:14, 13 August 2013 (UTC) A reader