Software in Medical Devices, a blog by MD101 Consulting

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How to develop a smartphone App to be FDA-cleared or CE Marked? - part 4 Usability

In the last article, we saw the concerns about the reliability of wireless connections and how to handle them.
Today, we are going to have a look at something quite important for mobile platforms: usability and humans factors engineering (HFE).

Usability and risk assessment

Generally speaking, usability can be seen as a source of data for risk assessment. Usability studies mainly focus on misuse of devices. Misuse may be a source of errors thus a potential risk.

Context of use

The usability of a device is very dependent on its context of use: who uses it and where it is used.

Professional use

In a professional context, mobile platforms are mostly used by medical or paramedical personnel to do their job when:

  • they are on call and not present in their health care centre,
  • they are in their health care centre but not close to the patient they treat or the medical device they work with,
  • they are in an ambulance, or any land/air/sea vehicle in an emergency context.

In the first two cases, the context of use is roughly the same as classical (non-mobile) platforms. The nature of errors and misuses found in usability studies realized in this context aren't very different from those for non-mobile platforms.

In the last case, usability studies are a critical part of risk analysis, hence the context of use can be very peculiar. There is a cultural habit of manufacturers of devices used in emergency, to know and foresee potential hazards. This habit may not be a characteristic of mobile software manufacturers, which want to enter the market of devices used in emergency.

Home use

In a household context, the person using the device may be the patient itself. It may be a patient's relative. It may also be a nurse or another professional like home help.
Things can go wrong very quickly, in this context. Users may suffer from disabilities, they may not be trained to use the device, they may be disturbed by the environment (dimmed light, poor network connection, yelling TV set!).

In this case, usability study becomes a critical part of risk assessment. The lack of, or an incomplete usability study may lead to a situation where easily discoverable hazards remain unveiled.

Man machine interface

Man machine interface is another source of misuse, be it the hardware part or the software part.

Hardware

Small screens are undoubtedly a source of misuse or degradation of ease of use. Likewise, touch screens aren't as accurate as mouse pointers. Small size combined with low accuracy of touch screen represent a potential source of misuse hazards.

Graphical user-interface (GUI)

It is usually difficult to read long text on a small screen. It also difficult to catch the working of a graphical user interface with all the bells and whistles (that's why responsive design was created).
GUI, which require users to concentrate themselves on what they're looking at, are a potential source of misuse hazards as well.

On top of that, in the context of home use, many users aren't comfortable with mobile platforms. Mix all these potential sources of hazards together (small screens, GUI and users) and you have a situation where usability studies are deemed worthy!

Standards and guidances

Two main standards are recognized by the FDA, for usability:

  • IEC 62366 Medical devices – Application of usability engineering to medical devices: a very generic standard, which describes a usability engineering process to follow. It is also an harmonized standard in Europe.
  • AAMI HE75 Human factors engineering - design of medical devices: a comprehensive standard on HFE, with chapter 21 dedicated to software, chapter 24 to mobile medical devices, and chapter 25 to home health care. This standard is not harmonized in Europe.

IEC 62366 standard is often criticized for its complexity. A 2nd version should be released in 2014.

FDA guidances

Like in many cases, FDA is the sole source of information. There is no guidance published by other regulation authorities in the rest of the world.
But FDA opinion on mobile devices evolves from time to time (see below).

Human Factors Engineering

You may have a look at the webpage on human factors program at FDA to see how things are going on about these guidances (see links on the right of that webpage).

Home Use

There's no final guidance on this topic yet. You may also have a look at the webpage on Home Use Devices Initiative at FDA to see the opinion of FDA about home use of medical devices.
One draft guidance about home use: Design Considerations for Devices Intended for Home Use

Conclusion

While Human Factors Engineering is with no doubt a good way of reducing the risks of misuse of medical devices, the standard and regulatory framework is still a work in progress. IEC 62366 is expected to change dramatically in its 2nd version, and latests FDA guidances are still in draft status.



Next time, we'll see mobile apps deployment.



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