60601-1 BF vs CF determination

We have an infusion pump-type device which are classifying as a Type CF applied part, based on the fact that all other infusion pumps appear to be classified as Type CF. However, we are re-evaluating whether Type CF is appropriate classification. I have noted (a) that nearly all infusion pumps are Type CF, (b) that there are some infusion pumps that are Type BF, and (c) all intravenous blood warmers appear to be Type BF.

As far as I can tell, there should not be a difference between the classification of these devices as BF vs CF. (all are connected to patient catheters) Please let me know if you have any advice or experience defining these requirements.
 

Tidge

Trusted Information Resource
The argument I've always heard(*1) is something like: "while in use, there exists a path(*2) between the heart and our device."

(*1)I don't mean to imply there isn't another argument, just that I don't remember ever hearing another one.

(*2) Folks who say this almost always mean "electrical path", but I've met at least one who did not!


I have long-suspected that the "path", no matter the actual length, for these types of devices is not credible as an electrical path...but when predicate devices have been approved as CF, I suspect that the expectation is that every subsequent device will end up being certified/labelled as CF.
 
The argument I've always heard(*1) is something like: "while in use, there exists a path(*2) between the heart and our device."

(*1)I don't mean to imply there isn't another argument, just that I don't remember ever hearing another one.

(*2) Folks who say this almost always mean "electrical path", but I've met at least one who did not!


I have long-suspected that the "path", no matter the actual length, for these types of devices is not credible as an electrical path...but when predicate devices have been approved as CF, I suspect that the expectation is that every subsequent device will end up being certified/labelled as CF.
This logic aligns with what I have come to understand as well. However, it is confusing that there are many devices with the same "electrical path" classified as BF. Thank you for your consideration!
 

Peter Selvey

Leader
Super Moderator
Only BF is required but CF makes sense commercially.

Type CF limits are derived from the assumption of small contact area with the heart, where very small currents (<100µA region) can cause fibrillation. The assumption in the standard is 1mm² (from memory, I need to check this). For a general purpose infusion pump, the point of access is well away from the heart and the current density at the heart will be very low. For reference you need about 40mA applied to a limb to get a risk of fibrillation around 1%. This is why 5mA is allowed for BF in the "mains on applied part" test (although in practice no equipment ever goes near this, it would pretty hard to design anything approaching 5mA @ 250V, that can also handle the 1500V test, i.e. 30mA!).

There is a related issue which is that the test of "mains on applied part" can only pass CF limits if the infusion set (tubing) is kept away from any earthed parts and connects only to the single infusion pump. In reality there's no guarantee of this, it could be touching bed frames, stands etc, and there can be other stuff connected to the circuit such as other pumps, IBP sensors, CO sensors and so on. So in reality, no infusion pump should ever pass CF. However, most test labs seem to be happy to overlook this, and test with the tube suspended in air and just the one pump. Obviously, noting the explanation above, it's not really a safety issue. But this could explain the odd BF device: it could be rare test labs that insist on the "mains on applied part" test being performed in a more realistic environment, and thus exceeding the CF limit and forcing a BF classification.

Commercially though, it makes sense to use CF if you can get away with it. Obviously CF == cardiac , and most people associate the blood circuit as more or less a direct path to the heart. If you don't know the details above, it kind of makes sense. Thus, if you don't want to have to repeatedly explain why BF is OK every time you want to make a sale, go with CF.
 
Thank you Peter! This is an extremely helpful and relevant answer. We've had a similar discussion with one of the test labs and their response matched yours, insofar as noting that BF or CF is acceptable. We are going to continue to investigation our options, but a Type BF classification may make the most sense here.
 
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