Rate of change alert: what value to set?

[Budapest]

I have been thinking about this since receiving the manual for the CGM that hopefully we are starting this coming week.

One of the alarms available is a rate of change alarm. It warns if the rate at which BG is changing (either up or down) exceeds a number that you set. The number is x mg/dl change per minute.

What number is reasonable to set? I could not find any info on-line and I kinda doubt our doc would have much useful input.

Is there a number at which medical professionals say it is not good for the body to experience such rapid change? Or maybe it could be approached from a technical point of view: Given the technical limitations of the CGM (15-20 min lag compared to finger stick etc.), is there a number to set the alarm to in order to help better catch lows?

What do you all think? I'd appreciate any thought on this confusing topic.

[jpb286]

Can you disable it?

Honestly I wouldnt want it, mainly because I have been on CGMS a week(Dexcom) and I would prefer NOT to have that feature. The body WILL spike after eating or crash after a large dose of insulin, and I discovered that even after giving a large bolus (>15-20u) there is still about a 45 minute window of "turnaround time" where as difficult as it is, I have to watch my BG continue to rise, force myself not to re-bolus, and waith for the insulin I just gave to kick in.

If you HAVE to set it, I would suggest starting higher like (change > 7mg/dl/min = alarm) and go from there. Personally I would find that alarm a huge nuisance.

[Budapest]

It is possible to disable it.

At the same time I'd think there is a reason why they came up with this alarm. There must be some use to it and some preferred setting whether medically/biologically or technically inspired. Don't you think?

BTW do you get this rapid rise and fall even with low GI food?

Any other ideas? Has anyone seen anything on different forums? I looked on the MM site as well but I guess they are careful not to recommend anything and leave it up to the docs. Maybe they said something at a nurse/CDE seminar?

Thanks.

[jpb286]

It is possible to disable it.

At the same time I'd think there is a reason why they came up with this alarm. There must be some use to it and some preferred setting whether medically/biologically or technically inspired. Don't you think?

Yes, it was invented for the sole purpose of keeping parents up all night.

BTW do you get this rapid rise and fall even with low GI food?
It doesnt matter what I eat, if it has carbs I get a big spike. I dont need an alarm to annoy me to the obvious.

Any other ideas? Has anyone seen anything on different forums? I looked on the MM site as well but I guess they are careful not to recommend anything and leave it up to the docs. Maybe they said something at a nurse/CDE seminar?

Out of ideas, but I would try it without the rate of change alarm for now and see what happens.

[bkfkmc]

Since we use the Paradigm system, we do not have the option for rate of change alarms. I think it is your preference of what you want out of the system as to what you choose to do. I have read parents on this board who were frustrated by alarms going off all night long. I am on the opposite end of the spectrum as I would rather know what is going on (within reason) since that is what I am paying the big bucks for! I have no knowledge of this feature and thus cannot recommend a good number. I would personally just find a place I felt comfortable starting and just tweak it as I go. As jpb286 pointed out, it may just keep you awake all night and not be worth the trouble. Since not many on this board have the Guardian RT, you are going where no man has gone before!:D You will be giving us advise when we get to upgrade!;) Good luck with your Minilink start!

[Rachel]

Do you have the one and two arrow feature too or is it just alarms? With ours (also not the Guardian RT) there is one arrow if there is a 20-40 mg/dl change over the last 20 minutes and two arrows if it greater than 40 mg/dl in the past 20 min.

We use this feature A LOT. As Paul points out, we usually see one and sometimes 2 arrows on the up and down-swing of the meal spikes, particularly at breakfast. I look about an hour or so after a meal to see where we are in the spike, then a little later to make sure it has peaked, and then a little later to make sure it is on its way down, etc. This allows me to correct for a high far sooner - if it plateaus or is just not coming down fast enough after about 2-2.5 hours, I'll correct, usually overriding the insulin on board number by half. I don't know that I'd want an alarm for this but I do like the arrows.

If I see an arrow at times other than post-meal, however, I know something isn't right.

And if I see arrows in the middle of the night something is definitely wrong and I would want the alarm on for that.

So, it would be interesting to see if you could set the alarm levels for different times of day - with a higher threshold during the day and lower at night. Or, how cool is this ... how about if they had it so the rate-of-change- alarm feature would simply disengage for 2.5 hours after a meal bolus?

[EmmasMom]

As you get started there will be more than enough alarms!;) I would probably start w/o it, and then use it as you learn for fine tuning boluses. In theory you can prevent a rapid post meal spike if you eat the right foods and bolus correctly, so it could be a great tool to see how you're timing boluses and how different foods are affecting your BG.
We have made huge strides in Emma's numbers using this data. We do this by watching the graph after she eats and analyzing reports, but you'll have some instant feedback which will be nice when you're making adjustments.

The low and high alarms, and predictive alarms will be your biggest help in keeping her in range, but I can see the value of the rate of change alarms once your used to the system.

Good Luck! :)

[Budapest]

Do you have the one and two arrow feature too or is it just alarms?
Yes, it has both.
So, it would be interesting to see if you could set the alarm levels for different times of day - with a higher threshold during the day and lower at night. Or, how cool is this ... how about if they had it so the rate-of-change- alarm feature would simply disengage for 2.5 hours after a meal bolus?
It seems, that only the high/low alert values can be different at various times of the day, but this effects the predictive alarm as well that predicts that in a x minutes the currently applicable high/low value might be reached.
The rate of change alarm is the same for the whole day.

BTW, there is another interesting setting on the Guardian that took me a few days to understand and I am still not quite there:D : AUC (area under curve): The AUC (Area Under the Curve) Limits feature measures how much and how long your sensor glucose measurements are above the pre-defined AUC High Limit or below the pre-defined AUC Low Limit.
This is independent of the High/low alarm settings. But for example, I still do not know what is the unit of measurement that tells both "how much and how long" :confused: Anyway, we will find out when we get the unit...

you are going where no man has gone before!

:cool:
We will experiment and keep you posted.
:)