IEC 62304 Section 4.3(a) - 100% probability of failure

yodon

Staff member
Super Moderator
#1
We have had an interesting internal discussion. Section 4.3(a) if 62304 says, when addressing the safety classification, “If the HAZARD could arise from a failure of the SOFTWARE SYSTEM to behave as specified, the probability of such failure shall be assumed to be 100 percent.”

The discussion arose about how this translates into the risk analysis. We're using an FMEA-type approach with severity / likelihood scales of 1..5.

In one school of thought, the failure WILL (100%) occur but the likelihood of it failing can still be considered (pre-controls). So a likelihood of occurrence of '1' (on the 1..5 scale) means that it WILL occur (thus meeting the 100% requirement) but it's still quite unlikely to occur over the life of use.

The other school of though is that, prior to mitigation, the likelihood must be 5 (to meet the 100% requirement) since it will occur at any given instance (and thus considering it occurring at the worst possible time).

We recognize that the root of the difference is the view (over the life -v- any given point in time).

Curious how others are approaching this. Maybe there's an entirely different method other than the FMEA approach that would be more suitable?
 
Elsmar Forum Sponsor

Marcelo

Inactive Registered Visitor
#2
Maybe there's an entirely different method other than the FMEA approach that would be more suitable?
Sure, and the approach is to follow ISO 14971.

A failure is one of the events in a sequence of events that might lead to a hazardous situation (which comprise P1). If the failure occurs (is 100 %) it does not mean that other events in the sequence of events will also be 100 %). Other events might have a different probability. So it means that P1 is not necessarily 100 %.

The failure has nothing to do with P2, so it also means that P2 is not necessarily 100 %.

Which means that the hazardous situation (P1 x P2) is not necessarily 100 %, too.

See the amendment to IEC 62304 and IEC 80002-1 for more info.
 

mihzago

Trusted Information Resource
#3
As Marcelo stated, there is a difference between a failure, and the failure resulting in harm to the user/patient. Make sure you define whether by failure you mean a defect in the software or an event that causes actual harm.

FMEA is not the best tool for a complete risk assessment because it focuses on the failure of the system rather than physiological harm*, and does not include normal use that may also cause or lead to harm.

(*ISO14971 also includes property and environment.)
 

glork98

Involved In Discussions
#4
This has come up a few times with the different organizations I've worked with. The basic problem is that is the failure rate is 100% and the harm is severe, or even moderate, then the product most likely does not have a benefit that outweighs the risk. This leads to a conclusion that a device that can do harm can not have SW in it.

I've taken two approaches:

The practical approach is to say that a failure is 100% initially and without any quality practices. That is, it's written and used and will fail. If this leads to an initial classification of B or C for the item, then apply the appropriate quality practices and that decreases the likelihood. Then reassess the failure for the need for further mitigation(s).

If the other staff (like SW quality) don't agree that quality practices reduce a defect's likelihood then add detectability to the evaluations. The RPN is then frequencyxdetectabilityxseverity. Use that failures are found by other SW and in test. (Also, ask why to do code reviews and unit tests if they don't decrease failures.)
 
Thread starter Similar threads Forum Replies Date
R IEC 62304 Section 5.3.6 Verify Software Architecture IEC 62304 - Medical Device Software Life Cycle Processes 4
K IEC 62304 - Functional and performance requirements for SOUP items IEC 62304 - Medical Device Software Life Cycle Processes 2
K IEC 62304 compliance - Code reviews as part of verification strategy IEC 62304 - Medical Device Software Life Cycle Processes 5
M Risk Analysis Flow - Confusion between ISO 14971 and IEC 62304 IEC 62304 - Medical Device Software Life Cycle Processes 8
D IEC 62304 Risk Classification - With and without hardware control IEC 62304 - Medical Device Software Life Cycle Processes 2
M IEC 62304 Class A Project IEC 62304 - Medical Device Software Life Cycle Processes 15
B Clause 5.1.12 of Technical Standard IEC 62304/A1 IEC 62304 - Medical Device Software Life Cycle Processes 5
P IEC 62304 - evaluation of integration and system testing IEC 62304 - Medical Device Software Life Cycle Processes 4
P Risk acceptability alignment between ISO 14971 and IEC 62304 IEC 62304 - Medical Device Software Life Cycle Processes 6
D Required Checklist Showing Compliance to IEC 62304 IEC 62304 - Medical Device Software Life Cycle Processes 11
P Proposed revision of IEC 62304 - 2019 IEC 62304 - Medical Device Software Life Cycle Processes 6
S Relationship between IEC 62304 problem resolution and ISO 13485 IEC 62304 - Medical Device Software Life Cycle Processes 8
P IEC 62304:2006 A1:2015 - Software from the early 1990s IEC 62304 - Medical Device Software Life Cycle Processes 4
B IEC 62304:2015 vs IEC 62304:2006 + AMD1 IEC 62304 - Medical Device Software Life Cycle Processes 4
F IEC 62304 - Segregation and communication between software items IEC 62304 - Medical Device Software Life Cycle Processes 1
B Class IIB Device - IEC 62304 Software Classification IEC 62304 - Medical Device Software Life Cycle Processes 13
B IEC 62304 - Update Checklist IEC 62304 - Medical Device Software Life Cycle Processes 2
L Connection between IEC 62304 and Chapter 14 of IEC 60601-1 IEC 60601 - Medical Electrical Equipment Safety Standards Series 2
M IEC 62304 - Develop an Architecture for the Interfaces of Software Items IEC 62304 - Medical Device Software Life Cycle Processes 8
S Does IEC 62304 require documenting unresolved anomalies for all safety classes? IEC 62304 - Medical Device Software Life Cycle Processes 4
A SOP for software validation of software in medical device IEC 62304 IEC 62304 - Medical Device Software Life Cycle Processes 5
T I need to make test reports according IEC 62304 & IEC 62366 IEC 62366 - Medical Device Usability Engineering 2
D Changing software classification via software - IEC 62304 IEC 62304 - Medical Device Software Life Cycle Processes 3
D Software as risk control - Confused on one aspect of IEC 62304 IEC 62304 - Medical Device Software Life Cycle Processes 20
K Trying to figure out what satisfies a few aspects of IEC 62304 IEC 62304 - Medical Device Software Life Cycle Processes 2
Y Application of IEC/EN 62304 at an advanced stage of software development IEC 62304 - Medical Device Software Life Cycle Processes 4
T Is there any requirement to be compliant with IEC 62304 while implementing ISO 13485 ISO 13485:2016 - Medical Device Quality Management Systems 5
L Documentation Planning - IEC 62304 Clause 5.1.8 IEC 62304 - Medical Device Software Life Cycle Processes 2
C Software for Medical Devices - Requirements Content for compliance with IEC 62304 IEC 62304 - Medical Device Software Life Cycle Processes 1
W CPU BIST IEC 62304 - Embedded code has CPU instruction tests IEC 62304 - Medical Device Software Life Cycle Processes 2
K IEC 62304 Amd 1 2015 - Figure 3 – Assigning Software Safety Classification IEC 62304 - Medical Device Software Life Cycle Processes 11
K Risk Reduction by Risk Control: IEC:62304-Class C ISO 14971 - Medical Device Risk Management 15
C Per IEC 62304, are DHF documents Configuration Items? IEC 62304 - Medical Device Software Life Cycle Processes 5
P IEC 62304 AMD1:2015: What's new vs.the 2006 Edition? IEC 62304 - Medical Device Software Life Cycle Processes 4
F FDA PMK 510(k) - IEC 62304 Software Components Segregation Other US Medical Device Regulations 3
M IEC 62304 Applicability - GUI Control Software IEC 62304 - Medical Device Software Life Cycle Processes 3
B Our NB says that IEC 62304 is an ISO 14971 Requirement ISO 14971 - Medical Device Risk Management 1
B Clarification on interpretation of some EN ISO 14971:2012 & IEC 62304:2006 req's ISO 14971 - Medical Device Risk Management 46
H ISO 14971 vs. IEC 62304 vs. 98/79/EC vs. ISO 13485 (Software Medical Device) ISO 14971 - Medical Device Risk Management 1
D A desperate call for help - IEC 62304 software IEC 62304 - Medical Device Software Life Cycle Processes 5
B IEC 62304:2006/AMD1:2015 Changes for Class A Software IEC 62304 - Medical Device Software Life Cycle Processes 3
M IEC 62304, ISO 14971 and FDA Medical Device SW Guidance 21 CFR Part 820 - US FDA Quality System Regulations (QSR) 5
K IEC 62304 - Compliance steps IEC 62304 - Medical Device Software Life Cycle Processes 2
K ISO 14971 and IEC 62304 - Medical Device Software House ISO 14971 - Medical Device Risk Management 9
S Software Test Report including IEC 62304 classification IEC 62304 - Medical Device Software Life Cycle Processes 4
A Mapping of IEC 62304 artefacts (SRS, SAD, etc) to the 820.30 phases IEC 62304 - Medical Device Software Life Cycle Processes 5
W IEC 62304 vs. IMDRF SaMD Guideline Risk Class IEC 62304 - Medical Device Software Life Cycle Processes 5
C New IEC/TR 80002-3 Guidance for IEC 62304 - June 2014 IEC 62304 - Medical Device Software Life Cycle Processes 2
R IEC 62304 was brought up during an FDA Inspection/Audit IEC 62304 - Medical Device Software Life Cycle Processes 6
O Electronic Fever Thermometer - Why not IEC 62304 Class C? IEC 62304 - Medical Device Software Life Cycle Processes 7
Similar threads


















































Top Bottom