July 19, 2012

Diabetes Pump & CGM Integrated on a Cocktail Napkin

I got into a rousing conversation about the possibility of over bolusing based on CGM information over drinks at FFL. To be specific we were talking about over bolusing or stacking insulin based on high BGs on a CGM screen. I started drawing on napkins at which point there may have been a case to be made that I over bolused beverages.
Someone pulled out their pump CGM combo and showed a little tick mark that indicated a bolus. Good start. However I think it would be great to see more. How about putting the insulin on board on the CGM trend line as an area chart. This would be a clear visual there is IOB. 
This IOB area would be linked to what ever the pump uses for IOB calculations. For simplicity imagine it runs off evenly over three hours. So when you bolus it puts a little triangle on you CGM screen. The peak is the total units bolused and it slopes down over three hours to zero. So if just after at 6:00 pm bolus for a quick dinner your CGM would show IOB reaching out beyond the current time.  Say something like this:

If you extended the bolus it would take a different shape. The point still is to make IOB clear on the integrated pump cgm screen. 
Say that bolus was part of an imaginary day that started off okay with overnight bouncing around 130. You pre-bolus a little for breakfast and manage to only spike a little to about 200 and work your way down. Dash for lunch try to pre bolus a little spike a little more but come down too much. - because what is a day without a low? Grab a juice to treat the low and pre bolus for dinner. At the time you pre bolus maybe you day’s cgm IOB looks like this: 

(BG scale on the left IOB on the right.)

Brilliance right? And it only took a few drinks.