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Tweaking a Split Bolus

In the preceding article, Advanced Pump Features, we talked about when to use a Split Bolus.

Remember:
If:
  • there's an initial drop in blood glucose followed by later high blood glucose, and
  • the meal was low GI, high protein, and/or high fat, and
  • the basal rates, I:C ratios, and carb content have all been confirmed as accurate,
Then:
  • a Split Bolus may be helpful for smoothing out the post-meal valleys and peaks.

If that is the case, we suggested that you experiment with the Split (Dual Wave/Combo/Multiwave/Extended Bolus feature of your child's insulin pump: try an initial combo bolus, monitor blood glucose closely (wise whenever you mix up the management routine!) by checking and recording the blood glucose results at 1-hour post-meal and a few times (1-2 hours apart) in the hours following the meal. This will give you the data needed to determine the effect of the Split Bolus.

But where should you start? And what should you do with the results?


Where to Start with a Split Bolus

An appropriate split of the Normal and Extended portions of the Split Bolus depends upon a number of factors, including:

  • the GI of each of the foods eaten
  • the combination of foods eaten (Is your child eating a large proportion of low-GI foods? Mostly moderate-GI foods? Mostly a high-GI food with some small amount of low-GI food on the side? Each of these situations would benefit from a different insulin split.)
  • the fat and protein content of the meal
  • individual differences

We suggest that you wade into the (Dual) Wave with a conservative starting point, and carefully analyze the results.

tips from the trenches of type 1 diabetesThere is no magical starting point for experimenting with a split bolus; the numbers will be different for each individual. So we can't tell you exactly how to do it, but we can tell you our story...
When we're trying out a new food that we think needs to be combo'd, we often start with a 50/50 split over 3 hours. That is, 50% of the meal bolus will be delivered up front, with the remaining 50% being infused slowly over the following 3 hours. The BG response gives clues as to how we might do things differently next time (or not). ~Danielle


How to Adjust the Split Based on the Results

If your child just ate pasta using a Split Bolus for the first time, and the resulting blood glucose flat-lined at 6.0 mmol/L for the following 12 hours, then congratulations! Your experiment is done.

But for the other 99.9% of us, a bit of post-experimental data analysis would be helpful. Here are some things to consider:
If blood glucose drops early in the meal despite the use of a Split Bolus, this may indicate that too much insulin is still being delivered up front: try a smaller number for the 1st part of the ratio. For example, if your initial split was 50/50, you could try 40/60, or even 30/70.

Conversely, if blood glucose rises significantly early after the meal, this could mean that not enough insulin is being delivered up front: try a larger number for the 1st part of the ratio. For example, if your initial split was 50/50, you could try 60/40, or even 70/30.

If blood glucose is steady for the first few hours around the meal time, but rises suddenly a few hours after the meal, this may indicate that the insulin "tail" is too short: try spreading the extended portion of the bolus over a longer time period. For example, if initially you used a 50/50 combo over 3 hours, you could try extending the same split over 4 hours.
tips from the trenches of type 1 diabetesI keep a notebook in the kitchen with a page for each common "problem meal", like spaghetti and meatballs, rice and beans, or rice noodles with stir fry. (The list of "problem meals" is finite, and relatively short for us.) When my son eats a certain meal, I make note of the split and the time period we used, and then record the BG results over the next several hours until the combo has expired and all the insulin has been delivered. Looking at the BG results, I then decide whether that combo configuration worked or not, and whether the results were bang on, close, or an epic fail. Then I analyze the results as outlined above AND write down a suggestion too myself for what to do next time. After a few meals of a given type, I can look back at the collection of results to see patterns and adjust my approach.
~Michelle


Split Bolus Not Enough to Manage Post-Meal Spikes?

For meals with a high fat content, you may find that, in addition to using a Split Bolus to address slower digestion, it may be helpful to set a temporary basal rate increase to address the insulin resistance that comes from fat intake. In these cases, check out the Double Whammy Approach in WaltzingTheDragon.ca's Adjusting for GI Level page.



Any questions? Comments? Feel free to Contact Us.


The above information was reviewed for content accuracy by clinical staff of the Alberta Children’s Hospital Diabetes Clinic.

This material has been developed from sources that we believe are accurate, however, as the field of medicine (in particular as it applies to diabetes) is rapidly evolving, the information should not be relied upon, as it is designed for informational purposes only. It should not be used in place of medical advice, instruction and/or treatment. If you have specific questions, please consult your doctor or appropriate health care professional.


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