Alarm “AUDIO PAUSED” of infant incubator

[william guo]

Hello experts,
A question about the AUDIO PAUSED requirements in IEC 60601-2-19, which requires that "the audio paused for an infant incubator warming up from cold condition may be up to 30 min", how do I measure the time under this audio paused condition, or how this condition canbe simulated?
BR
William Guo

 

[Tidge]

I am not familiar with that particular standard. My experience with other particular standards informs what follows in this post.

Presumably, there is an ALARM CONDITION for 'cold' that would trigger ALARM SIGNALS, including an audible component. My guess is that this particular standard is is acceptable to allow the audible component of the ALARM SIGNAL to be AUDIO PAUSED while the incubator warms up, but no longer than 30 minutes.

My naive expectation is that when an incubator is first turned on, that it generates an ALARM SIGNAL because of the ALARM CONDITION that it is not warming the infant. Presumably an operator can pause the audible part of the ALARM SIGNAL, but for no longer than 30 minutes. If so, then I can think of a couple of test cases:

1) Standard operation: turn on the device and see that the ALARM CONDITION clears prior to 30 minutes (subject to whatever alarm latching is in the particular standard)

2) Challenge test of AUDIO PAUSE: Turn on device but defeat the 30 minute warm-up (using dry ice? Keeping the lid open? Disconnecting the warming element?). After pausing the audio, make sure that the audible part of the ALARM SIGNAL is heard prior to 30 minutes.

 

[Peter Selvey]

Just to add some more detail:
There is an technical alarm in -2-19 if the measured temperature is not inside the control band (±3°C) after steady state is achieved. This would be the main alarm that needs to be paused up to 30min to allow for warm up. Also there are alarms if the baby sensor is disconnected, again which might occur during warm up as the nurse is organising the infant.

I personally would first look at the algorithm in the software to see how COLD CONDITION is determined, and then develop challenge conditions based on that to test various key aspects. It's important not only to test the 30min pause in warm up, but that there is no normal condition might also trigger the same 30min pause even after the system is warmed up. For example, if the incubator is moved from one room to the next, power supply is briefly interrupted, does the software see this as cold condition? If yes, it's a mistake.

 

[william guo]

Hi Tidge and Perter,
thanks for your inputs. -2-19 refer the definition of "COLD CONDITION" to the general standard, which is "condition obtained if electrical equipment is de-energized for a sufficiently long time to attain the ambient temperature".
I think the case sequence maybe
1) the infant incubator is working normally and achieved a stable temperature condition
2) An alarm conditions occurred such as fan stop or high temperature
3) the incibator detected the alarm condition and generated an audio and visual alarm, simultaneously, the power of the heater was cut off.
4) the healthcare person response to the alarm and takes some actions with a deliberate "audio paused"
5) Alarm condition cleared and the incubator starts to warm up
Question is, how the requirements of max. 30min audio paused time from warm up apply? because only if the alarm condition was cleared, the incubator can warm up, may be from the "COLD CONDITION".
BR
William

 

[Peter Selvey]

The example doesn't really work since it's a hardware fault that probably needs the infant transferred to a new incubator (the fan in a normal incubator is not easily accessible especially while the infant is in there).

I expect it's not too hard to differentiate between conditions to decide when the 30min pause is OK. For example, modern systems usually have non-volatile RAM which can be used to tell the difference between a normal power off and a power interruption, and most systems would have real time clocks that can tell how long the interruption is as well as sensors to assess if everything has cooled down. With all that information, it shouldn't be too hard to develop an algorithm that makes sense, i.e. find the balance between minimizing false alarms while maximizing the alarm when needed.

It's not a perfect solution and even 30 min is a little arbitrary. The point is that simplistic software solutions such as power off (whatever reason) = cold condition = 30 min alarm pause would be wrong since there are low cost solutions that are better.

In reality, the audio pause is intended for warm up while the infant is not in there which is the normal way, you don't put the infant in while the incubator is just turned on). So an more ideal solution might be to use the incubators scales to tell if the incubator is empty or not