All of the factors you mention can be important to determining the life of the device from a reliability point of view. An FMEA will help you determine the factors.
Typically, you are looking for factors that cause the device to fail in use, as opposed to early failures, often called infant mortality.
Consider vibration as an example. Your analysis might reveal that the vibration in use over 10 years, say, could cause the device to fail. For reliability, you would want to determine the failure cause and strengthen it. For reliability demonstration you would find a way to simulate 10 years of normal vibration in six months calendar time. This is acceleration part.
Factors that affect device life may interact, so this means you should test them together instead of one at a time. For example, you might design a test in a heated saline filled container to accelerate corrosion and accelerate component failure.
The classic book, the gold standard, is Accelerated Testing by Wayne Nelson. I like Applied Reliability, third edition, by Tobias and Trindade.
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Dan O'Leary CQA, CQE
Swanzey NH
United States
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Original Message:
Sent: 04-Mar-2022 01:50
From: Jayaram Abimanyu
Subject: Accelerated Life testing for Active Implantable Medical Device
Hi Dan,
Thank you for the great insight which I will definitely look to explore. You said in electronic systems, temperature is one of the common acceleration factor, what about vibration or combined vibration-temperature acceleration factor to be considered for the portable body worn externally fitted devices communicating to the implantable unit. Do we need to consider actual implantable conditions like saline filled chamber to conduct this acceleration life testing..
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Jayaram Abimanyu
Bengaluru
India
Original Message:
Sent: 01-Mar-2022 09:43
From: Dan O'Leary
Subject: Accelerated Life testing for Active Implantable Medical Device
This is a reliability question, which is a HUGE field. I don't know of any guidance documents, but IEC has a large number of standards in this area.
The method is simple to explain. First, determine the reliability goal for the system. There may be an industry standard or publication from a trade group that that help you determine an appropriate reliability goal.
Conduct a reliability analysis using techniques such as reliability block diagrams and FMEA to determine if the system would meet the reliability goal. Change the design as necessary.
Do a reliability demonstration. In this case you need a plan that describes the kinds of failures that count. For example, you could an optional feature that, if it were to fail, would not impact the device functionality. If you are going to do an accelerated life test you need to determine what causes failures and how to accelerate the failure rate. In electronic systems, temperature is a common acceleration factor. They will also need to determine the sample size and the test duration.
This is all statistical analysis, and if you have Minitab it can help you to design the test. There are many books available that can also assist.
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Dan O'Leary CQA, CQE
Swanzey NH
United States
Original Message:
Sent: 01-Mar-2022 02:47
From: Jayaram Abimanyu
Subject: Accelerated Life testing for Active Implantable Medical Device
Hi Dan,
This device has both non-implantable external device consisting of battery, processor and implantable electronic device both work together. Both battery change and calibration done externally. I just want to understand as a system to perform accelerated life testing, what are the test conditions to be considered or there any guidance documents available to get more insight on this.
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Jayaram Abimanyu
Bengaluru
India
Original Message:
Sent: 28-Feb-2022 09:34
From: Dan O'Leary
Subject: Accelerated Life testing for Active Implantable Medical Device
Because the standard does not have any specific requirements, you will need to analyze your specific device. Because it is an active device, it is powered, so what is the source of the power. It could be a concentional battery or one charged by magnetic induction. Do you need to remove the battery to replace it? If so, do you need to explant the device. Battery life is one condition.
Another is calibration. Does the device need calibration? If so, can the calibration happen without explanting it. For example is there a way to read the settings and adjust them while still implanted. Calibration frequency is one condition.
Reliability of the electronics is a major factor. There is a wealth of literature on how to conduct accelerated life testing.
Look for FDA guidance documents for the device. Also look at ISO 14971:2007, D.6.5, Example 3 for a discussion of cochlear implants.
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Dan O'Leary CQA, CQE
Swanzey NH
United States
Original Message:
Sent: 28-Feb-2022 05:43
From: Jayaram Abimanyu
Subject: Accelerated Life testing for Active Implantable Medical Device
Hi All,
What are all the accelerated life testing to be done for the active implantable medical devices as per ISO 14708-1 and ISO 14708-7. Because in the standard there is no specific mention of it and to prove its reliability and safety, what specific life tests to be done to claim it's service life. Could you please provide your guidance or thoughts on this.
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Jayaram Abimanyu
Chennai
India
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