re: "Basic Safety" versus "Essential Performance"
A key difference is the use of the word "direct" in the definition for basic safety.
Historically, IEC 60601-1 (1st and 2nd edition) defined safety as relating to direct harm. Examples were electric shock, mechanical injury, burns, ionizing radiation etc that come directly out of the equipment. Direct harm also includes functional parameters of higher risk devices when significantly out of control, such as surgical lasers, infusion pumps, dialysis, ESUs and X-ray, and special issues such as air infusion, bolus or blood loss from a detached blood circuit.
Indirect harm, typically related to misdiagnosis or performance out of spec but not directly harmful was not strictly under the scope of 601, although it slowly found it's way into the series via particular standards and arguably some of the requirements in 601 such as the need to declare the accuracy of indicated measurements.
The 3rd edition changed the definition of a safety hazard and removed the word "direct".
The standard has retained the concept of "direct" through the definition of "basic safety". The rational explains this is harm "incidental" to the main function, which although in many cases is good for a rough guide, it is not strictly correct according to the definition.
As with the second edition, direct harm can also be caused by the main function of the device, if this is a high risk function which is out of control, such as a surgical laser set to give a 10W 0.1ms pulse, which fails and outputs 100W continuously, burning a hole through the patient.
As most compliance criteria refers to both basic safety and essential performance, the distinction is not really a problem.
The main areas where it could have an impact are:
- Clause 4.3, which requires the manufacturer to list essential performance in the risk management file, and
- Clause 7.9.3.1 which requires the manufacturer to declare the essential performance in the technical manual (amendment 1 only)
Amendment 1 has also made it clear essential performance is to be considered in both normal and fault condition. This sets an overlap between the definition which needs to be addressed.
For example, in the case of an infant incubator, in normal condition we might expected the temperature control accuracy to +/-0.5C, while in SFC the temperature shall not exceed 39C. The normal condition is clearly essential performance. But the SFC falls under definition of basic safety, since it relates to physical harm directly arising from the equipment, and as such can be formally excluded from essential performance. But many would expect this to be included in the list of essential performance, and also declared under 7.9.3.1 (A1).
As for the design and testing, there is no effect, it just a matter of words in the risk management file and technical manual.
