Using a shorter averaging time ends up in a different "significant" apnea detection rate, i.e.less episodes of more than 20 seconds duration and more episodes of less than 20 seconds length.
It seems logical to redefine the significance based on other than the DURATION of apnea to some other markers that are more closely associated with cardiao-respiratory stability.
It is a good thought and we have been through this kind of debate for years. The 20-20 (20 s for SpO2
You first want to start with a very good pulseoximeter with top level performance in terms of artifact rejection resulting from motion, light etc.
When you have this you avoid already a lot of false alarms. Typically longer response time settings help the puls oximeters to deal with spurious noise.
In my opinion short resonse times like 3 seconds make no sense. You are interseted in central Spo2 but you measure on an extremity - there is a 10 to 30 second delay in blood travel time to the measurement site at the finger or toe depending on perfusion. Ear or forehead will be quicker but the reliabilty of signals at these spots is worse giving more artifact again. And if you have a true apnea, can you react in 3 seconds?
10 to 15 second is the best compromise setting.
We have published some work on this issue recently (Arch Dis Child Fetal Neonatal Ed. 2012 Sep 8. [Epub ahead of print]). I agree that having a very short averaging time will upset nurses. We are using 10 s for NICU monitoring, 2-3 s for sleep studies. The 80% cut-off for desaturation is arbitrary, mainly based on the level normally found in immature infants (it should be considerably below that), but I am not aware of a 20 s duration threshold, except for apnea. If it comes to desaturation, I would respond much more quickly. In any case, use of different averaging times may change the number of alarms you see by a factor of 6. Thus, you should be aware of what you are doing in this regard.
I feel that the sooner apnea is detected and appropriate intervention employed, the better for the baby. The practicability, however, of lowering the apnea detection (alarm) time to less than 10 seconds can be very demanding for all staff and may indeed become counter-productive. This is an interesting debate and I like follow comments from different parts of the world.
There are two issues being discussed here- the effect of the averaging time on the detection of desaturation events and what duration threshold to use to define an event. Although the trend in the NICU is to use a long averaging time to reduce false alarms, recent data (as stated by Christian Poets earlier) has revealed longer averaging times distort the waveform towards a falsely high number of events of >=20seconds. One work around would be to use a short averaging time to record the SpO2 waveform accurately but use a long monitor alarm delay to reduce the number of desat alarms. Although I have not checked the most recent Masimo alarm delays they have previously been limited to a delay of 10 seconds. I have not seen any data using a 20 sec delay.
As far as responding to short events, current discussions have focused on the reoxygenation phase of the event being associated with an oxidative stress response. If that is the case then leaning towards self-resolution or tactile stimulation instead of the use of supplemental oxygen (and most likely overshooting to a hyperoxic state) should also be considered. This is not an easy question to address.
It really makes sense to use some averages as the science in this is not sold. I would agree for a delay between 8-12 seconds.
What I really appreciate to see if the alarm is more dynamic with short delay time when the saturation below 70% and a longer delay time when it below 85%. I'm not aware of anybody had looked at this but I think it is a thought which should be evaluated. The babies who have BPD some of their episodes are profound and they spend more time in the low oxygen saturation range and it is obviously affect their long-term outcome. It will make more sense to interfere with them sooner before they get into dangerous hypoxic levels and they do not only suffer from the hypoxia they will also suffer from the reperfusion oxidative stress as demonstrated before.
The link bellow is a very timely addition to our discussion on apnea and monitors of short averaging time, enjoy
http://neonatalresearch.org/2013/06/01/apneas-are-alarming/?goback=.gmr_3738426.gde_3738426_member_246003413
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