EBME Forums Forums Free discussion Out of Hours Technology Medical Device Usability and Human Error

OK, let's get this one back into play.

How come that calculators, and numerical keypads on computer keyboards have 7-8-9 along the top row ... whilst telephones, mobile phones etc. have 1-2-3?

Which is better (more intuitive, or logical), and which should medical equipment use? Assuming, that is, that we want to standardise.

Meanwhile ... I have two "well known" infusion pumps right here in the workshop. One has the 1-2-3 layout whilst the other has (yes, you've guessed it) the 7-8-9.

Interesting question... I've just found that pages 24-27 of the NPSA Design for Patient Safety booklet recommends 1-2-3 layout to follow the wide use of mobile phones. And warn against mixing both layouts in the same context.

It also recommends considering chevrons and other analogue controls so the user monitors the screen more rather than punching in the keys as they will be more sure of their actions and less likely to check.

I've asked my colleagues but is there any more detail or science behind this?

I have always considered one of the "great leap forward"'s of medical machine interface to be the introduction of the Marquette (now GE) "trim knob" control (I may be a bit biased here as I worked for them at the time).

This simple interface control device allows the user to concentrate on the screen/menu/values/etc without the need to look at what their hand is actually doing. No various button pressing just a simple left/right movement and press to select. I think the evidence of just how good this interactive device was is just how many machines now use something similar.

Not nurse proof I'll grant you but simple and effective.

I also like the (so-called) "trim knob"* approach. But I first saw these on Dräger monitors (back in the mid-1990's). Not a lot of good on infusion pumps, though.

I also like the up and down chevrons on infusion pumps. A pair for each of the hundreds, ten, units (ones?) ... and (if need be) decimal positions.

Meanwhile, I have yet another "well known" pump in front of me now that simply has a 100, 10 and 1 button. Each press on each button increments by 100, 10 or 1 respectively, and then rolls-over to 0 again when you press again at 900, 90 or 9 (if you see what I mean). As always (and as Bruce sings in one of his songs), "you can get used to anything ... sooner or later it just becomes your life"!

* Twiddle and click? Very quick ... just as long as you can see what changes you are scrolling through, and then commiting to. Once again ... feedback!

Yes, it's called (visual, tactile?) feedback. Therefore "a good thing"!

Why?

Actually, you could be right there, Mate. Take a look at the old Terumo TE-311, for an example.

But my own take would probably have to be that the "trim knob" would be too quick and easy for insfusion pumps. Better, I reckon, to have something that enforces them (the users) to actually stop and think about what it is they are trying to do.

An example of that? Why, the "good old" MS-16A et al. Ha, ha.

Yes, quite, the MS16/26A, an example of bad user interface if I ever saw one.

However, what about the Omnifuse or that one that had the wheel thingy on the right hand end, um, err, the ....... (? sorry, it's late and my brain has slowed to a crawl).

Examples of "rotary switch interface" in infusion devices me thinks.

Ok, enough, bed time for me.............

... Terumo?

Meanwhile, here's the Omnifuse. I have never come across one of those myself. But, yes, that looks like an interesting interface.

How's that? It needs a tool in order to change the mm/hour (mm/24 hours) settings. Not a bad "design solution" considering its intended use, I would have thought. What's more, it has "stood the test of time", has it not? As usual, "less is more" (simple is best, whatever).