In practice, we sometimes receive the question: “nothing ever comes out of the safety measurements, why should we still do that? The electrical safety test almost always falls within the limits of the standard?”. We would like to share some insights on this.
We perform all these electrical safety tests to detect an exceptional defect in a medical device. This does not happen often, but we still want to be sure that the device is safe for the patient and user. However, we can do much more with these measured values.
Standard limits
The limits of IEC60601 and IEC62353 are related to what is safe for the patient. This means that for some measurements the limit value is, for example, 5000 µA, but the actual measured value is 61 µA. So a lot has to happen before the limit is exceeded. However, that does not mean that we cannot do anything with this measured value. When you perform a baseline measurement before commissioning, or take over the manufacturer’s baseline measurement, you can use this as a starting point for device-specific limits. The limits of the standard are the absolute maximum values. Of course, you can always use stricter limits at your own discretion. But what do we get out of this?
Device-specific limits
Device-specific limits help us to signal deviating developments in the measured values much earlier. Suppose that the measured 61 µA, before commissioning the device, suddenly rises to 243 µA after three years. Despite the fact that both values are still well within the limit of the standard, we can derive very interesting information from this. This development may indicate a defect, wear or, for example, deteriorated insulation of the device in question. If we only focus on the limit of IEC60601 or IEC62353, we will not notice this quickly.
New equipment
Is new equipment being put into use? This is a good time to start. Perform a baseline measurement according to IEC60601 and consider which device-specific limits would be realistic. You can then implement these in the device-specific (IEC62353) protocol. This is a proactive way to keep an even closer eye on the quality of the medical equipment. It can help you to observe deviating developments at an early stage and thus prevent worse.
