Thread: Woodlee

Hi Kev,

Get yourself a chain mail vest.. that will act as a nice faraday shield, plus it will offer a bit of protection from those 5mm chips flying off the shaper ..

I'm pretty sure that pacemakers are fully shielded these days, but still, I'd be doing a bit of research before welding, and asking the manufacturer of the device, what precautions you should take.

Regards
Ray

From the conversation I had with Kev, the doctors recommended only welding for short periods and not to close to the unit. As for what will affect it, thats over my head. Surely there would be something on Google about it, I might have a look latter.

Dave
PS
Luckily the gave him the super model, or he would have been modding it.

Originally Posted by RayG

Hi Kev,

Get yourself a chain mail vest.. that will act as a nice faraday shield, plus it will offer a bit of protection from those 5mm chips flying off the shaper ..

I'm pretty sure that pacemakers are fully shielded these days, but still, I'd be doing a bit of research before welding, and asking the manufacturer of the device, what precautions you should take.

Regards
Ray

Till he arcs it up when earthed out

Ray you'd think so, its not like you can avoid it even in daily life a walk down the road, factory visit even in suregrys Dr's say they prefer MP's turned of in case patients have them fitted. Now that one astounds me how do you avoid microwave signles ike those

Hi Woodlee, it can be a bit disconcerting having rhythm problems, I once spent a few days in hospital from the problem brought on by a combination of heatstroke and drinking too much caffeine.

A few years ago I spent a lot of time trying to shield interference from a 180V DC motor to a nearby battery powered computer board and gave it up after trying all manner of magnetic shielding, Faraday cages and electrostatic shielding.

All manner of isolation failed and the only thing that fixed it was using a higher frequency motor speed controller so that the voltage pulses were 10 times faster and then the current pulses were 1/10th the size (The stronger the current the stronger the interference) for the same average power. A modern solid state HF welder works in a similar way with lots of smaller current pulses compared to a 50Hz mains transformer.

I think once you get a VFD for your heart they sever the heart nerve to the brain so if your pacemaker went tits up from electric welder EMP who knows what would happen, it's certainly not worth the experiment. The only sure fire way to shield magnetism perfectly would be to encase yourself in a room temperature superconductor shield using the Meissner effect.

Its actually a lot more complicated than that - there is NO nerve from the brain to trigger the heart (its more like embedded processing ). The heart rythm is actually triggered by a few cells (the pacemaker node) inside the right atrium which have a calibrated chemical "leak" through "calcium channels" in the cell wall. This changes the polarity of the cells (potential between the inside and oputside of the cell wall) when a specific level of charged molecules have leaked and this repolarisation triggers other cells to conduct the resulting electrical impulse in a chain reaction from cell to cell across to the atrio-venrticular node. From there yet other cells (called the budle of His) which can repolarise as a result of this external stimulus conduct a chemical and electrical chain reaction to the ventricle muscle fibres almost instantanously to contract the ventricles (the pressure pump part of the heart).
Woodley's conduction system has failed somewhere along this path.
The implanted pacemaker replaces the electrical impules of repolarisation and electrodes are placed at the far side of the failed cells. So whichever bit still works fine is now triggered - or paced - externally.
When you consider the small number of cells and the very low level of potential change to make it all work, its all bloody amazing!

The risk to the system from external influences is not the pacing of the cells in the heart (which is very well shielded), but the PROGRAMMING of the pacemaker via the embedded coil in his body - which is obviously not shielded, because it needs to be accessed by an external magnetic programmer from time to time.

Very clever suff isn't it? That's why I'm so fascinated by it..... I guess it comes from my combined professional interests in both nursing and technology.
Cheers,
Joe

Kev said his model only works when it has to, so it just monitors his heart beat and then when it's needed it jumps in and takes over. I don't know much about them, but thats what he explained to me.

Dave

JHovel; I was under the impression that the vagus nerve connects the brain to the heart (as well as the stomach and digestive tracts) and acts to slow the rhythms of the heart so that severing it to the heart speeds up the heart rate. My only information comes from some old 1980's Electronics Australia pacemaker articles and a half drunken attempt to pick up a very attractive female Telectronics Pacemaker sales rep in the mid 1990's before they went bust.

Originally Posted by jhovel

Its actually a lot more complicated than that - there is NO nerve from the brain to trigger the heart (its more like embedded processing ). The heart rythm is actually triggered by a few cells (the pacemaker node) inside the right atrium which have a calibrated chemical "leak" through "calcium channels" in the cell wall. This changes the polarity of the cells (potential between the inside and oputside of the cell wall) when a specific level of charged molecules have leaked and this repolarisation triggers other cells to conduct the resulting electrical impulse in a chain reaction from cell to cell across to the atrio-venrticular node. From there yet other cells (called the budle of His) which can repolarise as a result of this external stimulus conduct a chemical and electrical chain reaction to the ventricle muscle fibres almost instantanously to contract the ventricles (the pressure pump part of the heart).
Woodley's conduction system has failed somewhere along this path.
The implanted pacemaker replaces the electrical impules of repolarisation and electrodes are placed at the far side of the failed cells. So whichever bit still works fine is now triggered - or paced - externally.
When you consider the small number of cells and the very low level of potential change to make it all work, its all bloody amazing!

The risk to the system from external influences is not the pacing of the cells in the heart (which is very well shielded), but the PROGRAMMING of the pacemaker via the embedded coil in his body - which is obviously not shielded, because it needs to be accessed by an external magnetic programmer from time to time.

Very clever suff isn't it? That's why I'm so fascinated by it..... I guess it comes from my combined professional interests in both nursing and technology.
Cheers,
Joe

Thats how it works and was explained to me by the heart specialist ,the electrical signal in my ticker is not making it past the second stage.
I'm waiting for an email from Medtronics the maker of the device with more information on welding.
Also have to collect a blue card from the heart specialist this week , this card I have to carry with me at all times , and present it at any airport security stations.
From the small info that I got from the heart guy the magnetic interference can fool the pacemaker into thinking that my heart rate is correct ,even though it may be running slow and the pace maker will not pace the heart .
Should return to normal function once the welding ceases.

Kev.

Great technology, isn't it?
Graziano, you are quite right, the vagus nerve slows the heart rate when there is a sudden increase in blood pressure. It does this by giving off a neuro transmitter chemical which reduces the speed of repolarisation of the muscle fibres so that they can't contract as quicly again. Adrenaline (and other cardiac stimulants) does the opposite.
I'd forgotten about that one..... (egg on face noted)
I did a little reading and could not find any references to vagus nerve cutting (vagotomy) at all. I did find discussion on the vagus nerve influence on artificial pacing and it was described as continuing to function normally, as it affects the ventricular muscles and not the electrical conduction mechanism.
Well, we all learnt something tonight! Good outcome.

Oh, I did also come across a warning about arc welding. Apparently the strong magnetic fields generated can prevent the pacemaker sending its signals. Incidentally there is one medical study that found that some headphones can do that if placed within one inch of the pacemaker.
Joe

Originally Posted by Woodlee

Hi fellow Blokes ,Shaper and shed addicts I'm out of the hospital and convalescing at home .
I'm sporting a new digital governor ( as Oldfraggle puts it) .

Like everyone else here I'm mighty pleased to hear that you're now home and doing ell Kev. I trust that it will all be smooth sailing from here on, and the discomfort from the surgery quickly recedes. Now if you could just fit a remote pot to your new digital governor Kev, you'd be able to out perform Sam the ram in a fresh paddock of ewes, (or should that be a paddock of fresh ewes). I can't believe that I just wrote that A bit like being 25 years old again and still knowing what you do now.
The actual mechanics of the heart as explained by Joe and Graziano are amazing that's for sure, and when you think how well the system operates in so many people for so many years giving almost no trouble, it is really staggering.
A quite funny and true story from some years back. At a paper mill I occasionally do shut down work at, the usual shut down co-ordinator was not present, and I asked one of the locals where TC (who was a great bloke and a real character) was, and I was told that he'd had a heart attack. He completely fooled us my informant went on. What do you mean I asked, and the reply came back, - "We didn't think the bastard had one". We had a good laugh, and I asked him to pass on my best wishes when he could. Well on my next visit about a year later, TC was back in full flight, and I related my conversation with the unnamed informant, and TC gave a hearty chuckle, and said that it had been "a hell of an operation, -nearly 5 hours, and the first 4½ hours were spent just looking for it". Needless to say we had another good laugh, he certainly never took himself too seriously, but he was the sort of bloke that every industrial complex needs, someone who fusses over the plant like a mother does to her child, just keeping everything running as smoothly as possible.
Well good luck with the fishing when the season starts Kev, now might be a good time to make plenty of new lures, and to check the rods and reels,
Best wishes,
Rob

I'd say my info is way out of date, cutting a nerve might have been something they did in the early days of pacemakers, the modern ones are a lot smarter in terms of what they can do and how they work in with the heart.

I can say that shielding a processor chip from magnetic interference is going to be nigh on impossible, from what I'd built with thick steel and earthed copper electrostatic shielding encasing a battery powered processor board. The processor incidentally is one also used for diabetes sugar monitors, a MAXQ2000 and of the 20 prototypes made four even ended up permanently crashing due to the flash memory being scrambled by the interference. The solution was to have minimal copper shielding and switch the motor speed from 100Hz to 1000Hz and no further problems occurred with interference as the magnitude of the interference was 1/10th smaller but ten times more frequent.

I'd consider buying a newer electronic welder (good excuse to get one too) as they produce less powerful interference pulses than an older welder that makes a wide range of harmonics blatted out all over the electromagnetic spectrum.

A new welder delivers it's power to the weld at at least 20 times as many pulses (50Hz vs say 1KHz for the electronic welder) so the current pulses are 20 times smaller for the same power setting. If the current pulses are smaller at the same voltage then the interference pulses are going to be smaller too, if more frequent.

MY arc welder is fairly old , but in very good condition , its a Lincoln Self Welder , made by the Lincoln electric company as a home shop welder .
Damn thing weighs a ton ,it was a give away from Lincoln (actually were given three of them ) , when I was purchasing new welding machines for the mine where I worked , we bought 50 large welders to be placed strategically all over the plant ,save dragging a welder when needed on the job .
I have long since desired an inverter welder ,having had one on our bush truck , the brand was Eutectic , rather expensive at $1400 , but a brilliant piece of kit , was also TIG capable .
I may look at getting a new welder a bit further down the track.

On a further note , I would like to thank yo all for the good wishes , your support is propping me up some what , Im not allowed near my workshop and being leg roped to the house is rather , well, boring. Watching Tv is not one of my favourite pastimes.
I have beem looking for the turbo switch on the pace maker to see if it ups my performace , when I do try I find I am inhibited by gout (ie the missus yells "g'out") So indoor sports are out as well.
Oh ,well back to the TV I guess.

Kev.

Its APIA Kev you can't even practice casting the rod. Not to worry you'll soon be back in the tinny hauling crabs.

Good on ya Woodlee, I enjoy your posts. but doesn't run.