Where to appeal a ridiculous IEC 60601 requirement?

Mark Meer

Trusted Information Resource
#1
Is there a means to appeal (and get a resolution in a reasonable amount of time) a 60601 requirement we think was ill-conceived?
 
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Mark Meer

Trusted Information Resource
#3
Specifically a requirement in IEC 60601-2-10:2012 Particular requirements for the basic safety and essential performance of nerve and muscle stimulators...

It states (with regards to output amplitude control):
"At its minimum setting, the output shall not exceed 2 % of that available at the maximum setting of the control."

Currently, ours runs from 1-40mA.
We have found that 1 to ~5mA pulses are virtually undetectable (i.e. no one is likely to use at these low settings), and 40mA is approaching the "very uncomfortable".

So, in order to comply with this requirement we'd have to:
a) Increase (double) the number of increments so that the minimum is < 1. As I say, 1 is already completely undetectable. Doing this would only severely impair the usability of the product.
OR
b) Increase the maximum to 50mA (which is potentially dangerous)

Both these options are negative: the first being pointless (and degrading product efficacy), the second being dangerous.

I understand the intent of the requirement (minimum settings should be sufficiently low to be safe). But it seems that expressing a required minimum in terms of a percentage of the maximum was a really poor choice...
 

Ronen E

Problem Solver
Staff member
Moderator
#4
Specifically a requirement in IEC 60601-2-10:2012 Particular requirements for the basic safety and essential performance of nerve and muscle stimulators...

It states (with regards to output amplitude control):
"At its minimum setting, the output shall not exceed 2 % of that available at the maximum setting of the control."

Currently, ours runs from 1-40mA.
We have found that 1 to ~5mA pulses are virtually undetectable (i.e. no one is likely to use at these low settings), and 40mA is approaching the "very uncomfortable".

So, in order to comply with this requirement we'd have to:
a) Increase (double) the number of increments so that the minimum is < 1. As I say, 1 is already completely undetectable. Doing this would only severely impair the usability of the product.
OR
b) Increase the maximum to 50mA (which is potentially dangerous)

Both these options are negative: the first being pointless (and degrading product efficacy), the second being dangerous.

I understand the intent of the requirement (minimum settings should be sufficiently low to be safe). But it seems that expressing a required minimum in terms of a percentage of the maximum was a really poor choice...
You could create a "test" minimum setting that would satisfy the standard, and state in your user manual that this setting is test-only and should not be used by the end user. You could even designate it as such on the control panel, if you're really concerned about usability.

What you are considering appealing is the standard wording itself, not an interpretation or a decision made based on it. As such, I don't predict a quick and successful outcome, regardless of you being right.

Ronen.
 

Mark Meer

Trusted Information Resource
#5
I guess we could create such a "test" setting at 0.8mA, but this would serve absolutely no purpose (except, of course to conform to that (ill-conceived) 2%-of-maximum requirement). The energies are so low, it's far below the ability to detect...

I wonder if one could interpret 0 as a minimum? If the control runs from 0-40, then wouldn't 0 be technically the "minimum", in which case anything goes...

As for the wording in the standard itself, I realize there is little hope of change (it having only been recently published in 2012). (sigh)
...but surely there are channels for industry to flag such concerns, so that they can be considered in future Corrigendums/Ammendments?
 

Ronen E

Problem Solver
Staff member
Moderator
#6
I guess we could create such a "test" setting at 0.8mA, but this would serve absolutely no purpose (except, of course to conform to that (ill-conceived) 2%-of-maximum requirement). The energies are so low, it's far below the ability to detect...

I wonder if one could interpret 0 as a minimum? If the control runs from 0-40, then wouldn't 0 be technically the "minimum", in which case anything goes...

As for the wording in the standard itself, I realize there is little hope of change (it having only been recently published in 2012). (sigh)
...but surely there are channels for industry to flag such concerns, so that they can be considered in future Corrigendums/Ammendments?
If you refer to changing the range from 1-40 to 0-40, then maybe 0 would satisfy the requirement. If, however, you referred to some "Off" state, my guess (which is not better than anybody's) is that it won't readily fly...

I'm not too familiar with IEC's internal workings, but I'm sure that such industry comments "depot" exists one way or another. I guess that if you contact your local branch (or however it's termed) they will be able to point you in the right direction.

Good luck,
Ronen.
 
Last edited:

Peter Selvey

Staff member
Super Moderator
#7
This is a very old requirement (from the 1987 edition), and on the face of it not unreasonable.

The intention is that the user should be able to start from a level that is basically undetectable and build up to a level that is comfortable.

In principle, the requirement is met by having an output control that starts at zero, but in practice there may be small currents e.g. impedance sensing to check good electrode contact, or just leakage across the hardware control component, so there must be some non-zero limit. A value of 2% is reasonable in this context. I expect most designers would likely target a nominal output of zero, but of course there may be small residual current depending on the design.

Just because the standard says 2%, and yours is 2.5% does not mean your device is unsafe. Limits are set based on a number of factors: safety, practicality, simplicity and "testability".

If for whatever reason this approach does not fit with your device, most modern regulations (EU, FDA, Japan, Canada, Australia to name a few) allow the manufacturer to document alternate solutions, i.e. justification based on the fundamentals of a particular device and situation.

The trade off is complexity in establishing a new limit. For this case if could could require clinical data or at least some literature. Anecdotal evidence would not be sufficient.

Current sensation can depend on a lot of factors, such as the electrode area, open circuit voltage, treatment location (current path), frequency, waveform (crest factor) and can also vary greatly with individual patients.

The claim that 5mA pulses are undetectable implies that the 5mA is the peak value, the pulses are relatively short so the rms value is significantly lower. Otherwise, it seems doubtful to claim that 5mA is undetectable.
 
W

wally4u

#8
Mark,
I assume you are referring to 201.12.1.101 * Output amplitude
I don't really agree with you that its an ridiculous requirement.

IMHO, the norm want to you to implement finer controls. i.e. <= 1mA increments.
That the patient cannot feel the initial steps 0.2mA doesn't really matter in this case, it's measurable with a scope and the 500Ohm load.
If you have processor, you could also increase the steps when you reach a certain threshold.

Also I don't agree that 50mA should be considered dangerous our equipment actually goes higher than that.

And 0 isn't a minimum, I would consider that just the OFF state.
 

Mark Meer

Trusted Information Resource
#9
In principle, the requirement is met by having an output control that starts at zero, but in practice there may be small currents e.g. impedance sensing to check good electrode contact...
In our system I'm pretty sure that 1mA or less is actually below the noise-floor for such detections. ...which is why values in this range really should not even be available via the control.

For this case if could could require clinical data or at least some literature. Anecdotal evidence would not be sufficient.
Current sensation can depend on a lot of factors, such as the electrode area, open circuit voltage, treatment location (current path), frequency, waveform (crest factor) and can also vary greatly with individual patients.
Agreed, that so many factors are involved. This makes clinical data or literature difficult to reference. We can only consult with researchers who have used similar technology setup, and they say that 5mA is the lowest detectable they've encountered (being the skinniest, most sensitive subjects), and the average being 20-30.

This however, despite coming from a reliable source, is still essentially anecdotal. There is no study that would specifically answer "what is the minimum detectable current using X technology". ...unless we organized a clinical trial ourselves (wishful, :nope:)

IMHO, the norm want to you to implement finer controls. i.e. <= 1mA increments.
That the patient cannot feel the initial steps 0.2mA doesn't really matter in this case, it's measurable with a scope and the 500Ohm load.
If you have processor, you could also increase the steps when you reach a certain threshold.
We operate (at per the standard) in "discrete increments". It would make little sense to have a whole tonne of tiny increments in the 'undetectable' range. This would just mean the user has to push buttons many more times to get to a level they can actually feel...

Also I don't agree that 50mA should be considered dangerous our equipment actually goes higher than that.
This depends on the nature of the pulse. Example: pulse frequency: the higher the frequency, the greater the potential current (see Table 201.101 in the standard).

Like I say, I understand the intent behind the requirement, I just think it is very poorly conceived/worded.
 
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