General requirements, tests and guidance for alarm systems in medical electrical equipment and medical electrical systems. Like nearly every technical standard, this is a long and detailed document that provides explicit instructions on nearly every conceivable alarm. It includes instructions on when alarms should be triggered, how their priority is classified, and perhaps most importantly, provides the different patterns that define exactly what the alarm will sound like. Signal burst pattern, pulse shape, pulse
One aspect of medical equipment that is often overlooked is the way the equipment communicates with its users. Visual indicators are incredibly useful, vital even, and can convey a significant amount of information in moments.
There are many challenges to designing medical equipment above and beyond the design of consumer equipment. In addition to higher reliability standards, medical equipment has more stringent and specific requirements. This makes sense as the stakes are much higher than with consumer electronics, where equipment failure is literally a life-or-death difference. One aspect of medical equipment that is often overlooked is the way the equipment communicates with its users. Visual indicators are incredibly useful, vital even, and can convey a significant amount of information in moments. However, they require the user to pay specific attention to the equipment. Audible signals, however, can catch the attention of people in and out of a room, leading them to come and review the situation and gain information. However, one of the challenges is that if there is a large variety of different medical equipment, which is more than likely in hospital settings, there could be a cacophony of confusing and
conflicting audible tones. Different frequencies, loudness, and patterns would require rote memorization of a large variety of signals, which would almost certainly add to confusion instead of clarifying. Thus, the IEC 60601-1-8 standard was created to provide guidelines to designers on how to create medical equipment that quickly and clearly communicates the intended message to doctors, nurses, and other attendants. This article will review this standard in more depth and help to decipher a few of the nuances involved.
frequency, rise/fall time, and amplitude are all given. There
are regulations given to separate alarms from technical issues where there are potential faults with the equipment itself versus problems with the patient. While these alarms are all well-regulated, it also explicitly allows for more sounds to be used, like music or voices. Outside of the more general guidelines, the IEC 60601-1-8 standard also outlines important technical metrics pertaining to medical alarms, such as: ■ The alarm frequency must be between 150Hz to 1,000Hz and must be one of four harmonics with the greatest sound level. ■ There must be a minimum of four frequency peaks between 150Hz and 4,000Hz. ■ The sound level of the greatest four frequency peaks between 150Hz and 4,000Hz must be within 15 dB of each other.
What is the IEC 60601-1-8?
As we start getting into IEC 60601-1-8, we should note where this actually comes from and the authority by which it is created and implemented. This was created by the International Electrotechnical Commission (IEC), a European- based standards organization that created the IEC 60601 technical standard that addresses all medical equipment. IEC 60601-1-8 is a subset that specifically addresses medical alarm systems. The verbose title of this subsection is:
IEC 60601-1-8 guidance for designing medical equipment alarms
Written by Jeff Smoot, VP of Apps Engineering and Motion Control at Same Sky
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