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"Farraday cage" or shielding for pacemaker user????

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  • "Farraday cage" or shielding for pacemaker user????

    My Dad had a medtronics pacemaker put in a few months ago. It's the simple pacer without defibralator.

    I've done a lot of googling, he's talked to his Doctor and to the company, and I've talked to a company rep....a friend of a friend who is an RN and supervises and services "new installations" but getting good info on pacemaker interaction with a plasma cutter has been difficult. The literature from the company is definite lowest common denominator, very general precautions dealing exclusively with low power stick and MIG welding.

    We've heard all the standard tips, (dry gloves&boots, twist leads, ground near weld, don't stand inside loop, less than 130amps, etc.) BUT NO ONE from the industry recognizes/admits there are different weld and cut processes.

    Plasma cutting is OUR main concern, but I suspect high frequency TIG would present similar issues.

    A google hit indicated a safe distance to electrical equipment (transformers and magnetic contactors) of 12" up to 200 volts AC, 18" up to 450 volts AC, and 24" up to 700 volts AC (These figures are approximate and subject to my poor memory.)

    My physics is rusty, but my question is:Could you build a Farraday cage or some other type of shielding into a welding jacket to deal with electro-magnetic fields that might throw the pacemaker into sleep mode? I know you can block radio waves with a cage, x-rays with lead, but what about magnetic fields?

    My medtronics rep. friend of a friend assures me we can't damage the pacemaker, but it may go to sleep and quit pacing. He also tells me they are making a model that can be put in MRI safe mode during imaging. Apparently the main obstacle was the leads getting hot and damaging the heart muscle tissue they are attached to.

    I'll beat the do-gooders to the punch.
    Q: Why take a chance?
    A: Life is a risk/reward situation and no one gets out alive. He won't take un-necessary risks. He'll have someone else run the machines if that is the only reasonable solution.

    Thanks,
    Scott

  • #2
    No, you cannot block low frequency magnetic fields (e.g. from large currents and transformers) with a faraday cage. You would need something like mu metal shielding, or some other kind of magnetic shielding.

    Comment


    • #3
      Originally posted by beanbag View Post
      No, you cannot block low frequency magnetic fields (e.g. from large currents and transformers) with a faraday cage. You would need something like mu metal shielding, or some other kind of magnetic shielding.
      Yep. I ve done a bit of magnetic shielding years ago to prevent stray fields
      from power supplies affecting CRT displays. At that time there was a Co. in
      Chicago that made several versions (for different strengths of fields) material
      in a "foil" form that could be folded etc and soldered to make enclosures.
      Don't see it as being very practical to use around ones chest though. :-(
      ...lew...

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      • #4
        No matter the type of plasma cutter power supply (transformer, inverter), it is generally some distance from the torch/operator , and that distance can be extended considerably to attenuate magnetic fields (low). Magnetic fields from a non-coiled wire/return are going to be very low. I'd be more concerned about the RF from the high frequency component of the arc, and although that could conceivably be shielded with a Faraday type cage, would you risk it without testing on 10 monkeys or 5 rabbits? Hey Dad, I think I figured it all out with my on-line buddies- go try it.

        Early pacemakers even warned about operating small engines (ignition arcs), like chainsaws and lawnmowers.
        Last edited by lakeside53; 03-17-2013, 12:40 PM.

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        • #5
          Ditto what Lew said.
          Paul A.

          Make it fit.
          You can't win and there is a penalty for trying!

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          • #6
            Thanks for the on topic replies Gentlemen.

            Mu metal rings a bell now that you mention it. I'll check into that a little

            It would not kill him to never pick up a stinger again, but it would be a shame...In his prime he was as good as anyone I've ever personally met, and better than most.

            He's about to start a testing process under controlled conditions with somebody else doing the process while he wanders around and feels the effects or lack thereof. Apparently, you cannot wreck the device, you'll just get faint if it is not pacing you sufficiently. Sounds like the defib. devices are a different kettle of fish. False alarms HURT.

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            • #7
              Wasn't there a warning about the early pacemakers when exposed to micowave ovens, especially in a fast food setting(Wendy's, Burger King, etc?).

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              • #8
                I could be totally "Out to lunch" here, but i thought those radar waves from automatic door openers caused some kind of problems also?

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                • #9
                  I think u need to dig up some more specific information as to just what kind of magnetic or electric signals are bad for the pacemaker, e.g. frequency and amplitude. Then see if there is a type of meter to detect that. Then worry about solutions.

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                  • #10
                    Originally posted by Mike Folks View Post
                    Wasn't there a warning about the early pacemakers when exposed to micowave ovens, especially in a fast food setting(Wendy's, Burger King, etc?).
                    If there was, I'd be to some degree surprised..... but it depends on the depth of implantation, or if it is implanted at all......

                    people do have some inherent shielding against electrical fields, since we conduct electricity to a fair degree, about like salt water.

                    Against magnetic fields, it is best not to bother trying to shield unless you have a specific spot you need shielded, a transformer, a sensitive detector, etc. "Area" or "volume" shielding against magnetic fields is not very effective unless a good deal of money is spent.

                    Generally, if you ask medical people, they DO NOT KNOW..... and so their response will be a blanket prohibition against anything you or they can think of that might possibly be electrical or magnetic. Essentially, if you have to ask, the answer is "no don't do that".

                    The manufacturer of the device DOES know, but for liability reasons, they WILL NOT TELL YOU beyond basic tested specs which they are required to disclose.

                    So most likely, the information which beanbag rightly thinks you should obtain is not going to be available.
                    1601

                    Keep eye on ball.
                    Hashim Khan

                    Comment


                    • #11
                      Originally posted by beanbag View Post
                      No, you cannot block low frequency magnetic fields (e.g. from large currents and transformers) with a faraday cage. You would need something like mu metal shielding, or some other kind of magnetic shielding.
                      I have zero expertise on pacemakers, but as an EE, I'd suggest the high-frequency RF from an inverter-based power supply, or the arc itself on a conventional transformer unit, would be much more dangerous to a pacemaker.

                      You could conceivably line a welding jacket with a flexible copper mesh which is then grounded, but there's no way I'd try that on anyone but myself.

                      A quick Google search turned up a salient thread on WeldingWeb (pro welding forum):

                      http://weldingweb.com/showthread.php?t=49008
                      "His Doctor gave him a pamphlet saying he could weld if he kept a distance of two feet away from the weld & the lead.Not always possible! Also it said that any effects would be temporary so if he felt any then stop and wait for heart beat to return to normal before resuming to weld. "

                      Holy crap that's hard-core: if the welder interferes with your pacemaker, stop welding until your heartbeat returns to normal.

                      ETA: An RF warning note from Hobart including grounding best practices. Mentions pacemaker use, if qualified by your doctor (i.e., the CYA Jerry mentioned).

                      http://www.hobartwelders.com/weldtal...0&d=1200846474
                      Last edited by lazlo; 03-17-2013, 10:56 PM.
                      "Twenty years from now you will be more disappointed by the things that you didn't do than by the ones you did."

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                      • #12
                        "So most likely, the information which beanbag rightly thinks you should obtain is not going to be available."-J Tiers

                        This is my exact gripe.

                        A thesis paper from Libya of all places gives a hint that "threat detectors" exist but the rep. I'm talking to has NEVER heard of such a thing. He is a good guy-He'd tell me if he KNEW. He is supposed to beat the bushes so we'll see if he can shake anything out of the geeks when the lawyers aren't around.

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                        • #13
                          Lazlo-that was the the single best thread I've seen on the subject. I'd scanned so many useless ones I'd kinda given up on forum results. I'll study the links within.

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                          • #14
                            How about a chain mail vest ? Sort of like the knights wore or shark suit vest ? Sorry I know this is off the wall but maybe.
                            Richard

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                            • #15
                              Originally posted by SVS View Post

                              A thesis paper from Libya of all places gives a hint that "threat detectors" exist but the rep. I'm talking to has NEVER heard of such a thing. He is a good guy-He'd tell me if he KNEW. He is supposed to beat the bushes so we'll see if he can shake anything out of the geeks when the lawyers aren't around.
                              It is relatively easy to detect all the interference that MAY affect a pacemaker.

                              The problem is to limit the detection to what WILL affect the pacemaker.

                              Without knowing the details of the pacemaker, I'd not have one clue as to what "hotspots" in the spectrum are a threat, and what isn't. Then also, the wiring from the pacemaker to the heart is also a variable.

                              While I totally understand the desire to know, It may be that nobody can be certain..... it could easily be determined what will affect the pacemaker itself...... it's the wiring and the person that we wouldn't know about for "certain".

                              Since the downside of any guarantee is large, while the downside of keeping mum is small, if I were involved with pacemakers, I would ALSO refuce to make any guarantees, and would issue a blanket disclaimer referring you to your doctor. It is the safe and prudent thing to do.

                              There are already so many issues involved with making the device to begin with*..... no way I'd want more.
                              .
                              .
                              .



                              * Read ANY electronic device datasheet...... from a microprocessor to a plain 805 SMT resistor.. Odds are that you are specifically directed that the device is not qualified for a list of usages, including life safety usages, medical, military, aerospace, etc......

                              To get parts that the maker will admit ARE qualified for anything past an MP3 player, usually requires either your own testing and qualification, or the signature of the device maker CEO, and it is generally hard to get the CEO to sign anything.
                              1601

                              Keep eye on ball.
                              Hashim Khan

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