No entanglement hazard of applied parts cables?


Starting to get Involved
Dear all,

I'm a hardware development engineer for polygraphic signal acquisition devices. New to this forum, so apologies up front if I have missed a thread that covered this already.

Identifying hazards frequently feels like kicking in open doors, but nothing surprises me anymore as even microwave manufacturers have to state that their equipment is not to be used for drying ones wet dog or cat...

Sub clause 9.1 has table 19, this is the only place in IEC-60601-1 where Entanglement HAZARD is mentioned. Trying to be thorough and equipped with a wild imagination I can foresee situations where people have ExG leads connected, or other applied parts, which could be highly uncomfortable when wrapped around ones neck, reducing blood circulation in limbs can be hazard enough.

The chances of entanglement with leads are not that remote, consider moving infants in incubators or with sleep diagnosis. So I would expect some warnings in the accompanying documentation of every lead manufacturer. But to my surprise I could not find any warning against entanglement hazards within the documentation of all competitors/colleagues/suppliers.
Is it because entanglement is not considered a hazard? Someone offered an explanation by stating that ?every medical professional gets instruction during their education how to use band aid to fixate applied parts, just to prevent getting hooked by a loose cable and to prevent entanglement. So plainly nobody sees it as a hazard?.
(But then I would expect a clear statement that ExG leads are only to be applied by well instructed personnel, which isn?t always the case either)

So what is it?
? No, applied part leads do not pose this mechanical hazard
? Yes, we should address this hazard in the RMF, and maybe in the user documentation.

I?d very much welcome your expert opinion.

Peter Selvey

Staff member
Super Moderator
It looks like there is a significant risk, but the question here is whether a label or a line in the instruction manual is an effective risk control.

It is reasonable raise the subject in the RMF, but it may be determined as having acceptable risk with no manufacturer action based on the use of qualified staff, with a note on the specific action that controls the risk (like taping the cords in place). Ideally a decision to take no action should be based on more than anecdotal evidence, instead relying on literature, review of incidents, or with formal input from identified qualified persons (e.g. a person who has worked at several hospitals over many years and can attest that the action is indeed well established). The fact that other manufacturers also have no action helps as support, but should never be the main argument for no action.

While these details should appear in the RMF (it might require a supplementary report if the space in the line item is not enough), there is no requirement to repeat the detail in the instruction manual. If the risk is already acceptable, no action by the manufacturer is OK.


Starting to get Involved
Thank you Peter Selvey for your swift reply.

According to Annex ZA of EN ISO 14971 :2012 point 5:
b) However, the second sentence of Section 2 of Annex I to Directive 93/42/EEC requests "to conform to safety principles, taking account of the generally acknowledged state of the art" and "to select the most appropriate solutions" by applying cumulatively what has been called "control options" or "control mechanisms" in the standard.
c) Accordingly, the manufacturer must apply all the "control options" and may not stop his endeavours if the first or the second control option has reduced the risk to an "acceptable level" (unless the additional control option(s) do(es) not improve the safety).
I know that 14971 and 93/42/EEC are more appropriate for other forums, but it is to show that considering the risk acceptable in the RMF does not dismiss a manufacturer of applying a warning of the residual risk in the manual, at least for CE labeling which most of the applied parts have.

Not seeing any warnings in current manuals makes me wonder whether other manufacturers consider it a risk at ll. I know now by experience that test houses and NB's are more focused on electrical safety and all other things they have nice applicable tests for. There is not an easy test for entanglement. So the chances of getting approved are quite high if one leaves the risk of entanglement by leads out of the RMF (or set it to "Not Applicable" like so many other items).

Of course there is the risk that adding too many warnings and exclusions make a manual into something unreadable that users want to throw away immediately. So one could make an argument in the RMF that adding a line in the manual would raise the risks of other more important points in the manual not being read. So it would be better to leave it out, hereby invoking the last part in parenthesis of the quote, point 5 c.
But I doubt that all these plain vanilla ECG lead manufacturers are even that philosophical.

Thank you for the tip regarding invoking the input of an identified qualified person. I expect to get some results by going our contacts in the local hospital, a box of chocolates in one hand and a bouquet in the other.:)
Could it be that in an entanglement event it is most likely that disconnection takes place, whether by the electrodes being pulled of, or connectors becoming separated?

This would reduce the hazard from possible strangulation to the nuisance of interrupted monitoring (and consequent alarm).

Perhaps in very small children / neonates the force they might generate would not be sufficient to disconnect. But, as far as I am aware, they are not usually sufficiently mobile to "roll over" so entanglement is less likely.

It would seem that direct medical professional advice might be helpful. Another source of information might be ECRI (a non-profit organisation - no connections) have just published their latest list of patient technology hazards -

but there is no mention there of entanglement.


I would recommend that you check if there are any collateral or particulars that are applicable for your equipment. they might have specific risk analysis requirements. for example it is not mentioned in 60601-1 about strangulation due to cables but it is a requirement to perform Risk analysis on strangulation in IEC 66001-1-11 (home healthcare equipments).

Also IEC 66001-1 3.1 edition clause specifies that hazards or hazardous situations that are identified for particular ME equipment or ME system but are not specifically addressed in 60601-1 or its collateral or particular standards the Mfr shall address those hazards in risk management process.

It is not necessary that you should only do risk analysis on hazards specified in 60601-1 but all the hazards related to specific device must be considered.

I hope this helps. :)
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