Wearing a Pace Maker and turning

[Marsden Champaign]

I recently became a pace maker wearer. After being,advised that I should maintain a distance of 2 feet from "powerful" electric motors, I have done no turning. I would like to hear their experience from turners with pacemakers.

 

[Bill Boehme]

I recently became a pace maker wearer. After being,advised that I should maintain a distance of 2 feet from "powerful" electric motors, I have done no turning. I would like to hear their experience from turners with pacemakers.

It is anybody's guess what the medical world thinks is powerful as opposed to how the engineering world classifies motors. It certainly wouldn't have hurt them to be more specific except that they naturally want to be overly cautious.

Modern Pacemakers and ICD's (defibrillator/pacemakers) have a high immunity to EMI (electromagnetic interference) from power lines, communications transmitters, cellphones, television sets, computers, microwave ovens, neon signs, radar, x-ray, MRI machines, and motors. You can hardly go anywhere without being exposed to one or more sources of significant EMI. There is not much magnetic flux leakage from most AC induction motors. The amount of EMI in the vicinity of an electronic variable speed drive might be a greater concern.

My dad and a cousin both have ICD's and have not experienced any problems around motors or other potential EMI sources. My cousin is a woodworker and has a large shop full of woodworking machines (no lathe) and has not had any problem with his defibrillator while operating any of he machines. Nobody should take risks if the potential interference is unknown. Here is a guide for Pacemaker and ICD wearers to help determine what is or isn't safe. I hope that this helps.

http://www.med.unc.edu/medicine/card/fellows/patientinstructions/EMI.pdf

 

[Marsden Champaign]

Thanks Bill. I appreciate the document re: sources of electromagnetic interference. It clears up some of my concerns.

My lathe is a Powermatic 3520b and my major concern is the Inverter.

I wonder if a metal shield in a vest has been tried by anyone.

 

[Bill Boehme]

Thanks Bill. I appreciate the document re: sources of electromagnetic interference. It clears up some of my concerns.

My lathe is a Powermatic 3520b and my major concern is the Inverter.

I wonder if a metal shield in a vest has been tried by anyone.

You might check with your cardiologist to see if your unit provides audible alert beeps if too much interference is detected or if not what symptoms would be noticed. I am certainly not qualified to say go ahead and use the lathe. I suspect that nobody could give you a an absolute answer since engineers can't answer medical questions and physicians can't answer electrical interference questions.

Safety guidelines are about all that one would be able to find. The thing about the guidelines for safe distance from certain equipment is that they include a very generous amount of safety margin. Also, the way that safe distances work is not like an ON/OFF switch. The intensity of interference increases as you get closer to whatever is causing the interference and eventually at some close distance, the level of electrical or magnetic interference will become a problem. The guidelines in the brochure provide known safe distances, but they obviously don't want you to be a human guinea pig who wants to find the true limits in his case.

There is one other useful bit of information. All non-communications electrical and electronic pieces of equipment are supposed to be certified to meet Part 15 of FCC requirements to not cause harmful interference to most other types of electronic equipment except for those that are only subject to Part 15. Originally, the intent was to not cause interference to communications equipment, but it has been expanded to include other types of equipment. I don't know where Pacemakers fit into this, but it would be worth contacting the FCC since this is an important question and could even lead to an NPRM (notice of proposed rule making). Unfortunately, some of the harmful interference regulations have been watered down a bit when politics has interfered with technical matters. A good example is foreign made computer subassemblies where the manufactures has been allowed exemption from the harmful interference rules by claiming that the system integrator is responsible for certifying compliance. As far as motor controllers are concerned, I think that their compliance with Part 15 is qualified to a certain test environment, but since they have no control over how the machine manufacturer installs and wires the controller, it is supposedly up to the machine manufacturer to certify compliance.

 

[John Lawson]

...I suspect that nobody could give you a an absolute answer since engineers can't answer medical questions and physicians can't answer electrical interference questions...

No, but I'm pretty sure the biomedical engineers who designed the pacemaker know the answer. The trick is getting to them and getting a straight answer not filtered through the legal department.

 

[Bill Boehme]

No, but I'm pretty sure the biomedical engineers who designed the pacemaker know the answer. The trick is getting to them and getting a straight answer not filtered through the legal department.

Because they do EMI/EMC testing, they know the susceptibility limits for various frequency ranges as well as induced currents from strong magnetic fields (such as MRI). However, that doesn't tell anyone what the actual conditions will be near any device that may produce interference because there are too many unknown variables and they can't evaluate these devices against every possible radiation source that exists.

 

[ray hampton]

what effect will a windshield wiper motor have on a pacemaker ? what about pacemaker and electric cars

 

[Bill Boehme]

what effect will a windshield wiper motor have on a pacemaker ? what about pacemaker and electric cars

It depends on your Pacemaker. The earliest models were very susceptible to interference from a great variety of sources. Those manufactured today, by comparison, are extremely tolerant of noise sources. The fundamental problem is that the electrical signals that control the heart muscles are extremely low level -- actually a much lower level that the ambient radiated noise levels that normally exists around us. The very small nerve signals have to be amplified several thousand times in magnitude to be processed by the Pacemaker. In order top do so without amplifying everything else, it was necessary to design amplifiers with heretofore unheard-of common mode rejection ratio gains of 120 decibels or greater while at the same time also minimizing inherent amplifier electronic noise. Advances in technology now enable the construction of ultra low-noise ampliers with extremely high gains and a CMRR far greater than 120 dB. Nevertheless, there is no such thing as perfect immunity to external noise sources. Additionally, there are some extremely high level sources of interference, both man-made and natural that will not only cause interference to Pacemakers, but will destroy any piece of electronic equipment.

 

[Marsden Champaign]

Good thoughts fellows. I'll check again with the manufacturer, Boston Scientific, and with my cardiologist about the beeping. I first tried the Boston Scientific web site expecting to find a forum and did not.I did not obtain any helpful info from them but that could well have been my fault since I was totally naive about asking for information.

 

[ray hampton]

I know what Pacemaker are but do not have first-hand experience with them, If storms or welding interference with A M Radio will they also interference with pacemakers

 

[Bill Boehme]

I know what Pacemaker are but do not have first-hand experience with them, If storms or welding interference with A M Radio will they also interference with pacemakers

If you open the link to the brochure that I referenced in my reply to Marsden, it will answer some of your questions. Arc welders (but, obviously not gas welders) are a hazard at very close distances. A direct lightning strike is a hazard, pacemaker or not. 😉 I suspect that very close strikes can also be a problem. None of the people who I know with Pacemakers have ever had a problem with lightning, but that's not to say that they may have experienced a skipped or extra beat. I think that patients with pacemakers may not be able to have MRI's since the magnetic flux density is up to 3 Teslas in the test section of some of the newer machines.

 

[Marsden Champaign]

My Boston Scientific pacemaker does not beep a warning of electromagnetic interference but their ICD's do.

Good question about thunderstorms as a source of interference..

 

[Marsden Champaign]

Bill you are correct about MRI's. My pacemaker guide book specifically warns against even entering a room that contains MRI equipment.

 

[Howard Beaver]

I admit that I'm unsure about any electrical interference caused by the MRI, but I certain the primary concern regarding MRIs is simpler than that. The powerful magnetic field tends to 'relocate' metallic objects that get to close to the field. This would include both the pacemacker itself, and the pacer electrode that caries the current to the heart. If you have any implanted device you must be vary wary of MRIs, unless you know fo a fact that the device is MRI safe.

 

[Bill Boehme]

I admit that I'm unsure about any electrical interference caused by the MRI, but I certain the primary concern regarding MRIs is simpler than that. The powerful magnetic field tends to 'relocate' metallic objects that get to close to the field. This would include both the pacemacker itself, and the pacer electrode that caries the current to the heart. If you have any implanted device you must be vary wary of MRIs, unless you know fo a fact that the device is MRI safe.

Well, it sounds like interesting Sci-Fi, but that is not what happens. The magnetic field is not a steady-state field and it can't "relocate" metal implants. The field generated by the MRI is actually a pulsed transverse electromagnetic wave with a very large magnetic field component. The helium cooled conductors in the electromagnet enables them to become superconductors to produce the huge currents that are necessary for the very short duration high amplitude magnetic pulses. Because the field produced is electromagnetic (i.e., the electrical and magnetic components are both time varying), it will induce eddy currents in any metallic conductor which results in what is known as induction heating. In the case of an electronic device, the results would be primarily very strong EMI (electromagnetic interference).

The operating frequency of the MRI is tuned to the spin frequency of the nucleus of hydrogen atoms found , of course, in water molecules of living tissue. These nuclei are all spinning in random orientations relative to one another. When hit with a very high intensity magnetic field, the spin axes of all of the hydrogen nuclei all snap into alignment with the field direction. At the end of the high frequency magnetic field pulse, the nuclei resume their random spin orientation and in the process, an extremely small amount of stored energy is released at the spin resonant frequency. It is during this very short "off" interval when no magnetic field is being produced that very sensitive receivers with directional "antennas" gather this data and merge it into three-dimensional data arrays that are subsequently used to produce cross-section views (aka, "slices") of the area being investigated.

 

[John Giem]

I admit that I'm unsure about any electrical interference caused by the MRI, but I certain the primary concern regarding MRIs is simpler than that. The powerful magnetic field tends to 'relocate' metallic objects that get to close to the field. This would include both the pacemacker itself, and the pacer electrode that caries the current to the heart. If you have any implanted device you must be vary wary of MRIs, unless you know fo a fact that the device is MRI safe.

My wife has had a pacemaker for several years. The problem with an MRI is the magnetic fields. When they do periodic checks at the cardiologists, they do several tests. During one test they place a magnet directly over the pacemaker to turn it off to check certain parameters. So, I think the biggest risk of an MRI is that it may just turn off the pacemaker. Howard is correct about the strong magnetic fields relocating objects. When I had an MRI, they did a special x-ray of my head because I do some metal working. They were looking for possible pieces of metal in or around my eyes. They did not want stray particle of metal moving around and causing damage.
My wife's pacemaker also has a recording capability built in. The tech reads this memory looking for any recorded 'events'. If the user was around any EMI that caused a disruption, then it would be recorded.
When we asked if my wife's TENS unit (electircal device for pain control) would interfer with the pacemaker, we were told to bring it in so they could monitor my wife while it was in operation. In her case, no problem.
Hopefully this experience will help.

 

[MichaelMouse]

Finally THE answer. It's not RF, it's magnetic induction you should fear. The fields which operate your motor are magnetic, of course, so don't lean your right shoulder or indulge in PDA with your lathe when running. Might touch your heart in other ways. In a word, induction.

The magnets in the MRI are quite powerful, so you should add that to your list of don'ts, along with the generator room at Niagara falls.

The new pacemakers are waaaay ahead of the first I encountered. I think the EMI warnings are a holdover from those days of ancient oscillators.

 

[ray hampton]

can a pacemaker be influence by a Magnetic Pull if it is made from copper or other non-magnetic metals or non-metal materials, as for metal in your eyes being attract by a MRI, the metal that are attract by magnetic force except stainless steel WILL rust in contract with your blood

 

[MichaelMouse]

Induced voltages. Your pacemaker has to read extremely low potential pacing signals from the SA node to determine if it needs to take over. When the wire's cut by magnetic lines of force, it generates electricity. http://en.wikipedia.org/wiki/Electromagnetic_induction It's moving electrons, not splinters.

Now an implanted defibrillator could be a real heart-stopper. http://en.wikipedia.org/wiki/Implantable_cardioverter-defibrillator

 

[ray hampton]

MichaelMouse , I found out that if a headphone speaker wires was rub on a piece of copper or other metals that it would produce static sound, it do not take much to cause induce voltage in a good conductor of electric, If you sandwich a sheet of steel and a sheet of copper with a insulated paper between them , passing a strong magnet over the plates will produce a current, my point is that even the wiring in the homes could be a problem in extreme cases

 

[Howard Beaver]

Bill

I cannot comment on your discussion on the electromagnetic interference, my education does not include significant depth in that field. I am just a respiratory therapist providing my limited scope of health care to my local community, trying to find time to turn wood.

I do know of a case where a steel oxygen tank, inadvertently brought into the MRI was relocated into the center of the magnetic field, precisely where the patient was also located. As these cylinder weigh approximately 30 lbs, I consider this a significant effect of the field.

My friends and co-workers that staff the MRI are frightfully anal about disallowing anything metallic into chamber, and I cannot fault them on this issue. No, I have stated I can comment on the electromagnetic interference, but I can state things moved.

PS. The patient did not survive the event.

Howard

 

[Bill Boehme]

.... When the wire's cut by magnetic lines of force, it generates electricity.....

Provided that the wire makes complete loop such that the magnetic lines of force pass through the loop. Also, the magnetic field has to be time varying (not steady-state). It is probably not so much the wires as it is the internal circuitry of the Pacemaker that is being affected. Since the magnetic field is being pulsed on and off at a super-high frequency, the radiated RF energy is a likely culprit.

I found out that if a headphone speaker wires was rub on a piece of copper or other metals that it would produce static sound, it do not take much to cause induce voltage in a good conductor of electric,

It sounds like you are talking about closing a headphone circuit with a wire being wiped across a piece of metal -- that would fall into the category of contact resistance noise which wouldn't be much different than a headphone jack that was making poor contact with the plug. That is not an induced voltage -- I would just call it a poor connection.

If you sandwich a sheet of steel and a sheet of copper with a insulated paper between them , passing a strong magnet over the plates will produce a current,

I'm sure that I am not following what you are saying. It sounds like you are describing a capacitor with one steel plate. If that is it, passing a magnet over it isn't going to produce anything because of the steel plate although you might be able to detect a current if you leave out the steel plate and just have a wire loop and move the magnet at very high speed through the loop.

my point is that even the wiring in the homes could be a problem in extreme cases

I do not see any connection between the previous statements and the conclusion.

 

[ray hampton]

Bill, my statement about using a ear phone wires and copper plate to produce static is not a bad connection but it were a make and break connection

 

[Bill Boehme]

Bill, my statement about using a ear phone wires and copper plate to produce static is not a bad connection but it were a make and break connection

That is the same thing -- I just said that it would be the equivalent to a bad connection in a phone jack because it certainly is not something that you would want although I occasionally run into that or comparable situations with other types of connectors when troubleshooting equipment. The main point is that this is not inducing a voltage into a circuit -- it is merely a poor noisy connection.

I ran into this same situation a few days ago when troubleshooting a friend's Powermatic 3520B in which a remote ON-OFF switch had been recently added. Its operation suddenly became erratic and upon troubleshooting the problem, I found that the switch contact resistance was so noisy that the closed-circuit impedance was varying from a couple ohms to open-circuit. Even though this switch is for starting and stopping the lathe, it is actually a "dry-circuit", meaning that it provides a high impedance logic input to the controller and it does not really switch the power to the mains.

One of the problems with the way that Powermatic designed this remote switch is that that they use a switch with the type of contacts intended for current carrying applications (i.e., "wet contacts"). It seems that even many design engineers do not understand that a special dry-circuit switch is necessary for this type of application that typically has bifurcated contacts to maintain low contact resistance and is not rated for current carrying applications.

Anyway, I sat in on the call while the owner called Powermatic tech support, I suspect that this is not the first time that they have heard this complaint because they immediately said that they would have a new unit sent out to him post-haste. That's nice, but they could have saved themselves money and the customer frustration by using the right switch in the first place.

 

[ray hampton]

the only three switches that I understand are knife switch , railroad switch and the switch to my back that I got when I were a bad kid, all other switches are made to be replaced not fix

 

[Bill Boehme]

Peach or willow?

 

[ray hampton]

Peach or willow?

neither, willow do not grow on hill top too often and we left the fruit trees limbs along but dogwood or sourwood were plenty supply

 

[Howard Beaver]

The safety manager inside me just can't let this go. There is serious risk in the MRI for anyone with any implantable device. True, some could be safe depending upon the material in the implant. Some electronic equipment might be affected by the magnetic field. But the primary danger is the field's ability to move these object.

I submit for you review this website:
http://www.simplyphysics.com/flying_objects.html

Howard

 

[Bill Boehme]

The safety manager inside me just can't let this go. There is serious risk in the MRI for anyone with any implantable device. True, some could be safe depending upon the material in the implant. Some electronic equipment might be affected by the magnetic field. But the primary danger is the field's ability to move these object.

I submit for you review this website:
http://www.simplyphysics.com/flying_objects.html

Howard

It seems to me that the anecdotal horror stories detracts somewhat from the professionalism and tend to make the site look more like a blog at times.

I don't know if it will allay some of your concerns, but almost all metal hardware implants such as hip joints, knees, pins, screws, etc. are non-magnetic stainless steel. They would not use anything that might corrode.

Unless you can point me to a document that indicates otherwise, my interpretation of "displacement" with respect to any implants containing ferrous materials is tht it means the patient undergoing the scan will not be able to maintain a certain position within the test section once the super-magnets are powered up as opposed to your interpretation that the ferrous implant will migrate within the person's body.

While there are safety issues regarding ferrous metal implants, there is also the technical issue of being to make a scan in the presence of ferrous metals. There is also another issue with any metal, ferrous or not; that' the problem of induced currents (known as "eddy" currents because of their circular path) that can result in induction heating from the strong E field in the test section. Besides induction heating, it has a worse effect of not being able to get a scan because of severe field warping caused by the metal object.

So far, at least 1,100 different types of implants have been evaluated regarding their safety to the patient as well as non-interference with the ability of the MRI machine to be able to make a scan. Some are OK and others are not. I have hardware in my back and in my chest and I have had well over 100 MRI's without a problem.

 

[Gretch Flo]

100 MRI's

I have hardware in my back and in my chest and I have had well over 100 MRI's without a problem.

WOW-Has your insurance paid for that machine????😀Gretch

 

[Howard Beaver]

I have hardware in my back and in my chest and I have had well over 100 MRI's without a problem.

Well Bill, I wholeheartedly disagree with you. The attitude is one pertaining to general population safety. If you know, beyond a shadow of a doubt that your implants are non-ferrous, then you can step up and have an MRI any time you like. My comments where for those that were not certain of the status of their implants.

Certainly, ferrous implants, or ferrous components within the implant can be affected by the magnetic fields in an MRI. The question was about a pacemaker in an MRI. I contend, that it is inaccurate to assume that all pacemakers are completely nonferrous in construction, and that all pacemaker patients are completely certain as to the exact makeup of their pacemaker.

I will let it rest here. If you have a pacemaker, I urge extreme caution with regard to any MRI diagnostic study until the exact safety of your particular pacemaker is confirmed for MRI studies.

Howard

 

[Bill Boehme]

Well Bill, I wholeheartedly disagree with you. The attitude is one pertaining to general population safety. If you know, beyond a shadow of a doubt that your implants are non-ferrous, then you can step up and have an MRI any time you like. My comments where for those that were not certain of the status of their implants.

Certainly, ferrous implants, or ferrous components within the implant can be affected by the magnetic fields in an MRI. The question was about a pacemaker in an MRI. I contend, that it is inaccurate to assume that all pacemakers are completely nonferrous in construction, and that all pacemaker patients are completely certain as to the exact makeup of their pacemaker.

I will let it rest here. If you have a pacemaker, I urge extreme caution with regard to any MRI diagnostic study until the exact safety of your particular pacemaker is confirmed for MRI studies.

Howard

Howard, I am not quite certain what you are disagreeing about. In nothing that I said, I have not stated that MRI's are safe across the board for all kinds of implants. In fact there are implant devices that do contain ferrous materials and many of those create a situation where an MRI can't be done, firstly because the amount of ferrous material makes it impossible to get a useable scan, secondly because there may be an unsafe level of induction heating, and finally because any significant amount of ferrous material will physically pull the patient towards the top of the tube. However, one type of implant, artificial joints, are normally made of non-magnetic stainless steel. That does not automatically make them safe because there might be a problem with induction heating or in some cases a magnetic stainless steel might have been used. The particular implants that I have do not have any adverse effects from MRI tests.

Early on in this thread, I provided a link to the OP and it unequivocally states that MRI's can't be performed on patients who have Pacemakers or ICD's. The ensuring discussion which was somewhat moot except for academic curiosity was mostly focused on the cause of interference to those devices. I believe that most everyone acknowledged that patients with Pacemakers can't have MRI's -- end of story. While the patient has the right to refuse any diagnostic test, it is the prescribing physician, radiologist, and technicians who have the expertise regarding what is or isn't safe. In my experience, they are always happy to discuss any concerns with the patient undergoing the test.

Here is a personal incident that served as a good demonstration of the field strength of an MRI machine. On one of my MRI's, I accidentally left the clothes locker key in the shirt pocket of my robe. I was wondering why it was taking so long for the scan to begin and after about 30 minutes several technicians came in and said that the equipment didn't seem to be working properly and they could not calibrate it for the scan. Then one of them noticed my shirt pocket stretched out and stuck to the inside top of the donut test section. That is when the key was discovered. They tried to leave the machine on and slide the key out by cutting the pocket off the robe, but it was stuck too tightly so they had to momentarily shut down the machine.

Regarding your callous comment about me 'having a scan any time that I like', I have never had a scan because I thought of it as some sort of entertainment. If I had my druthers, I wish that the situation was such that I had never needed an MRI and was still totally ignorant about them.

 

[Bill Boehme]

WOW-Has your insurance paid for that machine????😀Gretch

Probably, except it has been spread out over numerous machines all over the place. In the early days, it was a strange experience. There weren't many places to go then and they were always remotely located because of the high level of interference that they produced.