Without evidence of benefit, an intervention should not be presumed to be beneficial or safe.

- Rogue Medic

FDA takes steps to improve reliability of automated external defibrillators


 

Why improve the reliability of AEDs (Automated External Defibrillators)?

AEDs are important, much more important than the epinephrine I wrote about yesterday, because AEDs actually work – at least when the AEDs work as they are supposed to.

AEDs fail much more often than they should.
 

From January 2005 through September 2014, the FDA received approximately 72,000 medical device reports associated with the failure of these devices. Since 2005, manufacturers have conducted 111 recalls, affecting more than two million AEDs. The problems associated with many of these recalls and reports included design and manufacturing issues, such as inadequate control of components purchased from other suppliers.[1]

 

72,000 reports over ten years. In the US, there are about 300,00 cardiac arrests a year where treatment is considered and an AED might be applied. Out of those, how many times is an AED applied? 1/3?

If I use that ballpark number guess, then 72,000 out of 1,000,000 is 0.72%. The reporting of problems that are identified during equipment checks and maintenance should also decrease the rate of failure in the treatment of real patients. Maybe I decrease that guess at a failure rate during cardiac arrest treatment/assessment to 0.5% or 0.1%?

A decrease to 0.1% is one out of every 1,000 uses. Is that a tolerable level of failure for a device that has only two tasks, but has to remain ready to perform those tasks at all times? The two tasks are to differentiate between ventricular fibrillation/ventricular tachycardia and any other cardiac rhythm and to deliver a shock to the patient after ventricular fibrillation or ventricular tachycardia has been identified.
 


Image credit.
 

There are only a few moving parts and the designs may vary from what I describe. The wire that is manually attached to the defibrillator pads. The lids that is opened, turns on the AED, and triggers the voice prompts. The buttons that are pressed to turn on the AEDs not turned on by opening the lid, to analyze the rhythm, and to deliver the shock.

Would Do we accept a similar failure rate from an ambulance, which has many more moving parts?

Do we accept similar failure rates from our personal vehicles, which have many more moving parts?

Do we accept similar failure rates from aircraft, which has many more moving parts?

Yes and no.

We deal with the failures in these vehicles by building in redundancies and paying attention to maintenance, but the result is that the failures rarely cause death, or the lack of resuscitation that could have occurred with a properly functioning AED.
 

For example, NASA management claimed that they had an isty-bitsy teeny-weeny failure rate. They were shown to be wrong in a very dramatic, and deadly, fashion. Twice.
 

If a reasonable launch schedule is to be maintained, engineering often cannot be done fast enough to keep up with the expectations of originally conservative certification criteria designed to guarantee a very safe vehicle. In these situations, subtly, and often with apparently logical arguments, the criteria are altered so that flights may still be certified in time. They therefore fly in a relatively unsafe condition, with a chance of failure of the order of a percent (it is difficult to be more accurate).

Official management, on the other hand, claims to believe the probability of failure is a thousand times less. One reason for this may be an attempt to assure the government of NASA perfection and success in order to ensure the supply of funds. The other may be that they sincerely believed it to be true, demonstrating an almost incredible lack of communication between themselves and their working engineers.

. . . .

For a successful technology, reality must take precedence over public relations, for nature cannot be fooled.[2]

 

We need to understand what the actual failure rates are. We also need to work on the failure rate that comes from operator error.

The reason people are able to lie to us with statistics (statistics do not lie, but statistics can be used by liars) is that we choose to remain ignorant of the appropriate use of statistics. We ask to be lied to.
 

What is an acceptable failure rate? It isn’t zero, because a zero failure rate is a lie.

Footnotes:

[1] FDA takes steps to improve reliability of automated external defibrillators
January 28, 2015
Food and Drug Administration
FDA News Release

[2] Volume 2: Appendix F – Personal Observations on Reliability of Shuttle
Report of the Presidential Commission on the Space Shuttle Challenger Accident (Also known as The Rogers Commission Report)
by R. P. Feynman
Conclusions
NASA report

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