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PICList Thread
'[EE] Body-contact regulations and considerations'
2009\04\24@224818 by Jinx

face picon face
I've heard here many times that medical applicaitons require stringent
measures to protect the body from harmful currents, including running
devices on batteries

I'm looking at an application in which a PIC device will be in contact with
the body for prolonged periods

a) what sets medical devices apart from normal appliances that need
just plain fusing or are double-insulated ? For example if a device were
to be used on a foot (not my application) it's most unlikely that harmful
currents would pass through the heart for instance

b) who determines what a medical device is ? (if relevant). For example
I have a couple of  TENs units that do not seem to have much in the way
of special isolation. They run off a plug-pack and outputs are step-up
transformers. Perhaps they are actually lacking in the isolation department
and should be considered potrentially dangerous

c) would it be acceptable for example to have a reservoir battery and
trickle-
charge this with a solar cell and mains-powered light ? This affords much
protection and AIUI (amorphous ?) cells are reasonably efficient with non-
natural light

TIA

2009\04\25@072937 by olin piclist

face picon face
Jinx wrote:
> a) what sets medical devices apart from normal appliances that need
> just plain fusing or are double-insulated ?

If you have to ask you shouldn't be there.  Get out now while you still own
the shirt on your back.  At least here in the US, there are many complex
regulations, some that make sense and some not so much.  There are also
regulations on how you keep records of the design and manufacturing process
and a lot more.

This is not something where you simply read the manual and do what it says.
You need to go thru the process a few times with a organization that already
has the internal procedures and the culture for this.


********************************************************************
Embed Inc, Littleton Massachusetts, http://www.embedinc.com/products
(978) 742-9014.  Gold level PIC consultants since 2000.

2009\04\25@081414 by Jinx

face picon face
> there are many complex regulations, some that make sense and
> some not so much

Thanks Olin, I appreciate the comments, and not trying to be dim,
but what you said doesn't really answer my question. For example
there are many household appliances, such as stoves, heaters, lamps
etc, that run on exactly the same mains as found in a hospital and
quite capable of delivering no less a lethal belt than a faulty heart
monitor, yet they are, AFAICT, subject to a lower standard. Is a
heater in a ward a medical heater ? IOW, where is the line ? I can
make things as safe as they like. In fact I always endeavour to take
more than reasonable steps whatever the product, concerned as I
am with other people's well-being

I *will* enquire with the authorities after the weekend but thought I'd
ask here as well because I recall some members mentioning their medical
projects

2009\04\25@093155 by John Day

flavicon
face
At 08:12 AM 4/25/2009, Jinx wrote:
> > there are many complex regulations, some that make sense and
> > some not so much
>
>Thanks Olin, I appreciate the comments, and not trying to be dim,
>but what you said doesn't really answer my question. For example
>there are many household appliances, such as stoves, heaters, lamps
>etc, that run on exactly the same mains as found in a hospital and
>quite capable of delivering no less a lethal belt than a faulty heart
>monitor,

Any cardiac monitor built recently is almost incapable of delivering
anything like a lethal belt under pretty much any possible fault
condition. And will have been tested and ultimately certified to
prove it. It is more than likely that the power supply will have
3.5kV or more TESTED isolation, and then the low level analog
circuitry will be galvanically isolated from the remainder of the unit.

>  yet they are, AFAICT, subject to a lower standard. Is a
>heater in a ward a medical heater ? IOW, where is the line ?

When did you last see a heater running around lose in a ward?

>  I can
>make things as safe as they like. In fact I always endeavour to take
>more than reasonable steps whatever the product, concerned as I
>am with other people's well-being

We all should do that.

Any medical device whether it is in contact with the patient or not
is required to meet various regulatory requirements, be usually
designed and manufactured in accordance with standards such as
ISO9001 and ISO13485 and be certified by various national authorities
such as the FDA, Health Canada or whoever in the country where the
product is to be used. And also comply with various requirements such
as UL, CSA, CE, SAA or whatever other standards may apply as well as
the various EMC/EMI/RFI standards apply in each jurisdiction where
the device is to be sold. If the product you build/sell doesn't
comply with ALL of the requirements then even a huge insurance policy
may not save your butt. In some jurisdictions selling a non approved
medical anything can potentially land you in gaol. All of which helps
to account for teh cost of medical equipment!

>I *will* enquire with the authorities after the weekend but thought I'd
>ask here as well because I recall some members mentioning their medical
>projects

I may not have mentioned it before, but medical devices are what I do
every day and have been on and off for some 25 years.

JD

>

2009\04\25@101037 by olin piclist

face picon face
Jinx wrote:
> Is a heater in a ward a medical heater ? IOW, where is the line ?

That's the point.  It's not always clear and some things are up to the
interpretation of the regulating authorities and whatever the grieving
widow's sleazy lawyer can convince a jury of.

That said, a ordinary appliance that the hospital happened to buy and put in
a patient room isn't your problem.  As soon as you in any way claim it's a
medical device though, your regulatory problems start.  Anything that is
patient-touching is definitely regulated.  Everything else in the patient
room varies.

Lest you think this is just a joke, look up about cases where the FDC showed
up unannounce with armed marshalls and closed down plants.  Yes, they can do
that and they have.  Ask Baxter how their infusion pump business is going.
They were shut down by the FDC after excessive recalls and some
falsification of documents by service staff.  Last I heard the FDC isn't
even accepting applications from them about how they supposedly have fixed
their process, and I think a few former employees are headed to federal
prison.

> I can make things as safe as they like.

I'm sure you're quite capable of designing equipment to a reasonable
standard of safety.  That's not the point though.  There are various
regulations, some seemingly unreasonable that you'd never think of for just
common sense safe.  Then there are record keeping requirements you'll never
get right on your own.  Companies that do this have a full time person just
to make sure the records are in order.  The FDC can show up unannounced
anytime they feel like and demand to inspect your records, and yes, they
have teams of people whos job is to do just that.  They always find
something.  If you've been good you get to keep operating and are given some
time limit to fix the records and report back on your new procedure for
making sure it won't happen again.


********************************************************************
Embed Inc, Littleton Massachusetts, http://www.embedinc.com/products
(978) 742-9014.  Gold level PIC consultants since 2000.

2009\04\25@132756 by Steve Moulding

flavicon
face
Olin Lathrop wrote:
{Quote hidden}

Fully correct.  I spent 35 years dealing with these issues as the person in
a major teaching hospital responsible for electronic equipment  support.
Check out AAMI, JCAHO, FDA and NEC requirements (hint:  Google) for
electrical equipment requirements, and you will see some of the obstacles
you face.  Manufacturers such as Agilent, GE, Varian and Siemens (and the
hundreds of other major companies in the business) have huge staffs just to
research and keep up with the current regulations imposed on manufacturing.
The real killer is the FDA - if you have to submit for approval, be prepared
to expend hundreds of thousands of dollars for the process.  Our facility
had roughly 15 FTEs just to monitor compliance and another 150 or so whose
job requirements addressed electrical safety as more than half of their
duties.  That on the consumer end.  I know what Olin means when he says you
can never meet every requirement - there are too many and they change too
often.  We invested over 3/4 million dollars just for hardware/software to
track the inspection and servicing of electrical equipment in the facility.
Similar requirements are placed on every medical department and unit within
a health-care facility.  And folks wonder why medical care costs so much ...
I wouldn't want to discourage anyone from innovating new processes and
ideas, but the reality is that now you can only enter the medical device
field if you have megabucks to burn.  Find some other way to utilize your
time and ideas.

Steve



2009\04\25@144012 by Cdenk

flavicon
face
All the concern with equipment that may effect one (or a few) at one instant. Think about the bridges, roofs, vehicles, icluding racing events that can do many individuals at one time.

Once at a doctor's, I asked why the fee was so high, he said because they SAVE lives. I reminded him that a structural engineer had PREVENTED the roof from falling on him. :)
---- John Day <spam_OUTjohn.dayTakeThisOuTspamsiliconrailway.com> wrote:
{Quote hidden}

> >--

2009\04\25@160457 by Alan B. Pearce

face picon face
>I *will* enquire with the authorities after the weekend but thought
>I'd ask here as well because I recall some members mentioning their
>medical projects

My memories are that there are stringent regulations on earth return
currents for devices which have intimate electrical contact with the
patient - e.g. heart monitor, which is why there is a tendency to use
battery operated items where intimate electrical contact is involved.

Also devices that are intended for use in operating theatres, but possibly
also on wards may have requirements to be intrinsically safe, because of the
possibility of an oxygen rich atmosphere.

2009\04\25@182856 by Jinx

face picon face
> I wouldn't want to discourage anyone from innovating new processes
> and ideas, but the reality is that now you can only enter the medical
> device field if you have megabucks to burn.  Find some other way to
> utilize your time and ideas

Thanks for the insight Steve. Medical certification does sound like a
rocky road. As I mentioned initially, this isn't a **medical device per
se but it is in intimate body contact. The example I thought of last
night is a foot spa. Powered by mains, full of water and you have
body parts in it. And it is somewhat health-related. My uninformed
guess though is that it slips under the "medical" radar. If so, then I
should be OK, money-wise if nothing else

What I'm thinking of will run fine on a 6V or 12V SLA battery. If
that can be trickle-charged during operation with a solar cell and
light bulb that would be a bonus

** will have to get bureaucratic clarifaction

2009\04\25@184827 by Jinx

face picon face
> My memories are that there are stringent regulations on earth return
> currents for devices which have intimate electrical contact with the
> patient

The obvious one I should have thought of is an electric guitar or a
microphone. Intimate sweaty contact with metal for hours with just
a fuse or RCD between life on the road and a career-boosting early
demise

2009\04\26@120610 by Peter

picon face
Jinx <joecolquitt <at> clear.net.nz> writes:
> there are many household appliances, such as stoves, heaters, lamps
> etc, that run on exactly the same mains as found in a hospital and
> quite capable of delivering no less a lethal belt than a faulty heart

The short version: Medical grade devices (esp. electrical) are expected to be
used with 'open' bodies (contact wounds etc). That lowers the electrical
resistance of the body by removing the very high insulation provided by the
skin. The result is that the current needed to kill someone or cause pain is
much lower than 'with' skin, by a ratio of 1000:1 or so, and then there are
inter-operability issues between types of equipment. The leakage and grounding
(and not grounding - several devices are expected to be floating wrt. ground)
standards for medical and hospital grade equipment reflect this. Then they must
not create ignition sources (ether and some anesthetic gases ignite in air under
200 degrees C - so does Hydrogen if a catalyst is present - I heard cigarette
ashes contain such ...), plus there are power devices (like defibrillators)
which create immense input disturbances that should not destroy circuits and
also not create leakage that may cause trouble, even if they fry the circuits.
This is more or less the electrical side. The regulation side is very complex as
someone else observed.

Like everything else, there is a price tag on regulation (testing and
compliance) for such devices, and it is hefty. I heard that it is unclear
whether weapon system electronics or medical electronics are more expensive to
certify (this could be funny if it would not be sad).

Peter



2009\04\26@121508 by Peter

picon face
<cdenk <at> windstream.net> writes:
> Once at a doctor's, I asked why the fee was so high, he said because they
> SAVE lives. I reminded him that a
> structural engineer had PREVENTED the roof from falling on him. :)

I recently read a joke that proved by A+B that doctors are significantly more
lethal than lawyers *and* guns, based on official statistics ... it concluded
that the next step to reduce human mortality is ...

Anyway, a doctor is the one who patches up the failures of nutritionists and
hygienists as best as he can, aside from the occasional work or traffic accident
victim ;)

Peter

2009\04\28@084108 by Josh Koffman

face picon face
On Sat, Apr 25, 2009 at 6:47 PM, Jinx <.....joecolquittKILLspamspam@spam@clear.net.nz> wrote:
> The obvious one I should have thought of is an electric guitar or a
> microphone. Intimate sweaty contact with metal for hours with just
> a fuse or RCD between life on the road and a career-boosting early
> demise

And sometimes less than that. Old valve amps with non polarized plugs
spring to mind. Of course even with a grounded plug, ground lift
adapters seem to be the first tool to try to fix "that weird buzz".

Josh
--
A common mistake that people make when trying to design something
completely foolproof is to underestimate the ingenuity of complete
fools.
       -Douglas Adams

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