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Ask HN: Can anyone in the medical device/software industry explain redundancies?

12 points by _yoqn ↗ HN
How can we be sure that our life support systems, surgery robots, interventional radiology equipment et al will not fail at critical moments? Have there been any recent cases of a technical failure that led to major complications? For example, if a heart-lung bypass machine failed during a heart surgery the patient would certainly expire. If anyone with experience in this field could give a brief rundown it would be appreciated.

14 comments

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SkyPuncher
Not in the industry, but I suspect it's not much different than Avionics for safety critical parts: https://aviation.stackexchange.com/questions/3608/what-progr...

Basically, you work with low-level languages, be intentional about everything, and prove that the code you wrote works exactly as intended.

[dead] redis_mlc
Your comment doesn't make a lot of sense, since "prove" is exceedingly rare. In fact, most airline systems have weird failure modes after 30 days, 60 days, 2^n rollover, etc. that require a reset. Airbus planes were famous for needing a reboot after taxiing, for a few years (those appear to be fixed now.)

However, avionics devices are independent black boxes, and most non-trainer airplanes have redundant power buses, so usually there's power. (Trainers have a main bus and a relatively small automative-type battery.)

There is a move in smaller planes in 2021 to allow glass-only cockpits with no steam-gauge electric backups like AIs to save money, which most pilots thinks is a huge mistake. (No AI at night or in hard IFR would be fatal.)

The savings are about $2,000 at mfg. time, so you can see why people are side-eyeing this.

medymed
Regarding your example, a quick search shows a heart lung bypass machine has indeed failed during a procedure, the team use hand cranking/pumping to continue the bypass for 10+ minutes, and the patient did not expire.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4971270/

The paper seems to suggest this has happened quite a few times.

_yoqn
Fascinating that there is a hand crank somewhere on the machine. However this example is a tiny bit off as the point of failure in all the cases they mention in the paper were external power. I was asking more about redundancies in the equipment itself.
detaro
If your machine relies on external power, that is something you must consider and design around.
_yoqn
Fair point. I think this is cared for as all hospitals have backup power supplies and those supplies must be relied on. Last time I was in the hospital I saw red power outlets in the wall. I asked the nurse and she told me the red ones are hooked up to the emergency backup power.
detaro
There's almost guaranteed to be different levels to that too (e.g. allowed time for switch-over, interruptions, ... : emergency generators are far foolproof!), that need to be considered in the design. Emergency batteries in devices are not unusual.
readonthegoapp
There have been so many cases like this during covid

That im probably confusing some

But didn't one hospital in India just run out of oxygen in their wall supply? Everyone died.

davismwfl
I've worked on a variety of vital systems including some in health care. We defined vital systems as severe injury or death could occur if the system failed or failed unsafely.

The article dharmab linked is pretty well known and I think does a fair job of describing one of the key differences. Redundancy, reliability, durability and safety are not all the same thing in vital systems. In web systems and many other types of systems which are software driven, being redundant is good enough, not true in vital systems.

It is critical each device being designed must define what it means for that device to be reliable, redundant (if necessary), durable and safe. In some medical systems failing to a known safe condition is all that is required, in others the device needs multiple redundant systems to prevent a failure under a defined set of normal circumstances.

In health care failure of systems does happen, when it happens there are processes and procedures defined to manage them generally. In almost every case when a machine fails there is a manual method to take over. I've not worked on the radiological side (outside of some CV work), but I would assume they have separate systems monitoring exposures and causing fail safe shutdowns etc. That is generally the requirement (and common pattern) for any medical device that isn't supporting life, e.g. if it fails it needs to fail in a known safe state.

Honestly this is a huge topic I could ramble for a long time about, but in the end it comes down to defining requirements, defining outcomes, defining testing, testing and good processes to handle failure conditions.

davidrm
I'm in automotive, but we have similar requirements to medical.

There's no "100% fail proof" solution, it's about determining the modes of failure and addressing them individually and combined, minimizing the risk and defining an acceptable level of it. If you accept that failures are inevitable, which they are, some are likely, some vary rare, you can prepare for them via redundancies, fault tolerant design, etc.. It's also about doing proper system design and performing certain methodologies such as "Failure modes, effects, and diagnostic analysis" (FMEDA)[1], "Fault Tree Analysis" (FTA)[2] and accounting for those.

There are standards like IEC 61508[3], or its automotive adaption ISO 26262, with which certain engineering disciplines and fields must be audited against in order to pass certifications and be able to market the product. In case of ISO 26262 it's not mandatory (will be soon), but good luck explaining any judge or jury why are you the only company in the existence not applying it in your vehicle design.

[1] https://en.wikipedia.org/wiki/Failure_modes,_effects,_and_di...

[2] https://en.wikipedia.org/wiki/Fault_tree_analysis

[3] https://en.wikipedia.org/wiki/IEC_61508

boas
If the fluoro (X-ray) machine fails during a procedure, you can either bring in a portable C-arm, or move the patient (mid-procedure) to a different procedure room with working equipment.

If the power goes out and the backup generator fails during a procedure, people take out their cell phones and use the flashlight. If the patient is intubated, you can manually ventilate the patient.

If the equipment you need for an emergency procedure is not working, there is often an older, lower tech method to do the same procedure, or at least stabilize the patient.

If the electronic medical record system goes down, you can use pen and paper. Those records are then scanned in or entered into the EMR when it's back up.

Unexpected things happen a lot in medicine, so it's good to always have contingency plans.

Source: I'm an interventional radiologist.

dogleash
I'm not going to write you a crash course in medical device quality systems, but I'll mention the Failure Mode and Effects Analysis (FMEA). FMEAs are a core component of any risk management plan. In an FMEA, Failure Modes (what can go wrong) are identified and linked to Hazards and potential Harms that could result from the Failure Mode. The separate documentation that identified Hazards and Harms will have a Severity for each Harm. The FMEA will use that Severity and an engineering assessment of Occurrence probability for the Failure Mode to calculate risk. Mitigations (product requirements that reduce the likelihood of harm) are added until the occurrence is reduced to the point that residual risk is acceptable.

Further reading: ISO 13485 (quality system) ISO 14971 (risk management) IEC 60812 (FMEA)