Oatmeal has always been tricky for me but I've found I have luck with bolusing, waiting 15-20 minutes and then eating the oatmeal (this also works well with yogurt). This way you give the insulin a chance to start working before it gets hit with carbs that aren't super complex. You obviously don't want to do this if you are on starting with a BG on the low end of your range as you don't want to end up having to treat a low. Generally if I'm 80 or above, this method works fine and I'll set a timer too so I don't forget to eat with the insulin already on board.
This isnt really an application for a combo bolus. As you mentioned those work better on high fat foods where you are going to get a peak and then the fat will keep you elevated longer than other foods that break down and leave your system. Usually greasy food or even buttery popcorn are applications where I use the combo bolus.
I've only been pumping for a little over a year myself, and to be honest, I've never really figured out how to use the combo bolus either.
There are some foods that I just know I need to give myself another unit or two of insulin, such as bagels. Even if the package says it has say 50 g carbs, I will give myself another unit because inevitably I will still be a bit high a few hours later.
You might want to consider talking to your Endo about dropping (increasing) your Carb Ratio in the morning. I have the same issue as you have in the morning where my BG doesn't drop that much by lunch time. My Endo/CDE recommended increasing the amount of insulin I take for every gram of carb but only in the morning.
I love oatmeal! And the best one I have found is Vermont Morning (I think) Anyway I get it online - it is almost crunchy, flavorful - I think they add cinnamon. I always bolos for the total carbs - I do not deduct for fiber - that seems to work for me. The idea of dosing, then waiting is a good one. To use the Combo, I would start with a 70-30 split (70 now, 30 in a half an hour). Your pump should have the arithmetic for you.
It definitely takes some experimentation. First question is, are you bolusing 20 minutes before you eat, allowing the insulin to kick in? If you are, you can try starting out with a 70:30 bolus, which gives you 70% percent of your insulin immediately, and then set the number of hours you need that will allow the 30% to be out of there by lunchtime.
Oatmeal was tricky for me as well! Glad I'm not the only one. The trick that works for me without combo bolusing? I add about 1 T of peanut butter to my hot oat mixture (1/2 c regular oats, 1/4 tsp cinnamon, 1 T ground flax seed, 1 c water - nuke in microwave 4 minutes, then add 3 pkts Splenda). Just plop it in the middle, cover it up and let it sit for about a minute. The peanut butter gets nice and gooey and it is fantastically delish!
As for bolusing...just bolus as regular about the time you put the oats in the fridge. My bg's barely rise and are pretty much steady until lunch 3-4 hours later. It has worked great for me!
The typical oatmeal (rolled oats) does have a tendency to spike BG because it has been preprocessed. My doctor recommended what's known as Irish oatmeal (also known as groats or steel cut oatmeal). Because it is not processed like rolled oats it very low on the glycemic index.
I've been pumping for seven years and have been running a different I:C ratio for breakfast all along. Normally my ratio is 1:15 but breakfast is 1:12. Using the different ratio and the groats, I just take a normal bolus and have never had any issues.
I have oatmeal for breakfast every morning. On my package it says 60 gr carbs (net carbs) pr 100 gram, I go for 30 gram oatmeal (=18 gr carbs) and cook them with water for 5-10 minutes, I then add 100 gr blueberries (=7 gr carbs) and add some walnuts which I never carb count. To avoid a spike I have to bolus 20 minutes before I eat, sometimes 30 minutes if bg is 130. I don´t split the bolus but check after 1 h and then 2 h too keep an eye on how things are going. Most times it works. Hope you find what works for you.
I ate oatmeal for breakfast for many years, with mixed BG results. Eventually my body didn't like carbs in the morning. My I:C is 1:4 in the morning and 1:6 the rest of the day. If I eat over 18 or 20 carbs my postprandial BGs will exceed 140. I've done all the pre-bolusing experiments and some times work better than others. But sometimes you overdue the pre-bolus time and end up going low for trying to get too fancy.
But I gave it up. It was just too demanding.
The combo settings work best for protein/fat metabolism, especially in the context of limited carbs. I use a combo setting at every meal. It's a wonderful pump feature that consistently gives good results.
I agree with Terry about the combo bolus working best for protein/fat. I am in the habit of having a bowl of pistachios at bedtime. The combo is perfect for slow metabolizing foods like nuts.