Rule #1 of 670G Club: that word doesn’t mean what you think it means.
That’s what I’m told. Was kinda hoping I’d get some input on what adjustment to try from my MDT trainer today but haven’t heard back yet.
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I totally agree. Compared to a lot of people here or TuD I feel like I’m kinda middle of the road good at it, but when I see my Endo I realize I’m far out of the normal range. There’s a lot of self-selection: we’re only here because we want to deal with it.
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So, can you tell us what CR stands for, or do you need to be in the club to learn that?
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Carb ratio, duh
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If you read the post, you’ll see that is what I thought CR was, but DrBB said it was not what you think.
Isn’t that still what it stands for? Only the concept is implemented differently-- because obviously you’re not eating-- but it’s algorithm applies it in some other way with regard to what we would have traditionally called your insulin sensitivity ?
That’s why I was asking because apparently they are using CR for more than carbs.
Continuing resolution.
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Yes, that was what I meant. Same terms but what they refer to isn’t exactly the same because there’s a different underlying logic. You keep running across this because in a standard pump there’s this distinct thing, “basal rate,” that [isn’t the same as “microbolus” though it serves a similar function. In a regular pump it] refers to a setting of units/hr you’ve programmed in, and CR isn’t involved in that; it only kicks in when you’re eating carbs. Same with “correction” and “sensitivity,” because they’re distinct from whatever “basal” is set to do at any time. But in this pump there’s no longer as clear a distinction between those things and what it’s doing all the time. We had those more distinct categories as carry-over from MDI: “basal” was a whole different kind of insulin from what you used for bolusing and correcting. In a standard pump the distinction starts to break down to some degree because it’s just the one type, but it was still useful to think of “basal” as a totally separate thing because of how the programming works. But in a real body your pancreas isn’t thinking “Ok, now I’m just doing a basal… oops, now I’m bolusing”; it’s just going along excreting the stuff in response to metabolic signaling. It’s more of a continuum, and this thing is trying to model that more closely. As one of the more experienced guys on the user group said to me, “Insulin is insulin.”
Edited for a little clarification
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Good stuff to mention. I posted as while ago on TuD that, “your body doesn’t care if you call it basal or bolus, it treats it the same way”. That was before the 670G, so I wasn’t even talking about that particular pump.
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But in a real body your pancreas isn’t thinking “Ok, now I’m just doing a basal… oops, now I’m bolusing”; it’s just going along excreting the stuff in response to metabolic signaling.
I feel like this is a really important point, and long-term, my guess is the most effective artificial pancreas algorithms will get far away from the dogma of having an ISF, a basal rate and a Carb Ratio. It may be that there are more than three variables that will need to be modeled and accounted for. Or, another option is that essentially multiple variables can all be condensed into one parameter that is just constantly being adjusted. But either way the current method of tuning things will become obsolete.
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Before going on this pump I hadn’t given any thought to how historically/technologically contingent those terms are. We didn’t use them back in the R/N days, because those insulins were so low-res that bolusing for specific carb intake wasn’t even a thing. That nomenclature really came in with basal-bolus MDI, and carried over into pump tech because the metaphor still worked in that environment, but it’s already looking pretty frayed in “hybrid” land and will get more so, I agree.
The other nomenclature thing I’ve been discussing on the user sites is the problem with this term “auto mode.” For all that I’ve been trying to keep my expectations realistic, that “auto” term creates an expectation that this is going to be set-it-and-forget-it system. But like any other system, you have to massage the thing to make it work for you, and that is counterbalanced by various and subtle ways it wants to make you work for it. “Assist mode” would have been a better term, we think.
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@drbbennett, obviously we don’t use the 670G but I totally agree that assist mode is more like it, rather than auto mode. I actually probably spend a lot of time troubleshooting openAPS for my son – possibly more than I would managing his blood sugar minute-to-minute in manual mode. There’s certainly more complexity to juggle and it’s less straightforward.
But I think psychologically, the difference between manual and “auto” is huge. I’m mostly trying to troubleshoot parameters after the fact in a relaxed state later on in the evening, whereas when we were manually correcting via pump, time was always, always of the essence. I actually think I could achieve excellent control for my son using sugar surfing, etc. But I think the hassle of having to constantly check the numbers, to have to set my high alarms at, say 120 to catch upward trends, to respond to trends immediately, would eventually take a toll. While I do tend to be pretty obsessive about watching the numbers, I also have confidence that I can usually ignore them for an hour or two and even if he drifts high or low, some reasonable steps are already being taken by the algorithm to keep things from going totally off the rails. Obviously that doesn’t always work but I have confidence the algorithm is doing a reasonable first pass equivalent to what I would have done if I caught the trend, and in the best case, may actually be a lot better than my intuition.
I wonder if some of the frustration comes from that – people who excelled at blood sugar control have been conditioned to jump on trends immediately and to be really proactive, but that’s sort of difficult to do with the 670G.
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@drbbennett
I’m also on a 670G, and I found this thread while trying to figure out how to cope with how high my sugars are all the time. Yesterday I practically fell asleep at work because I was at 275 for four hours. It’s extraordinarily frustrating, especially with IOB calculations just assuming that whatever bolus I took for carbs is automatically insulin on board measured against any BG I give it (aka if I take 6 units for X carbs, and then 5 min later say I’m at 300 with an ISF of 30, the pump will just say “oh you have enough insulin on board, so no issues here”). I’m really curious to know what your solution for this kind of issue is, because I just can’t afford to have sugars this high for this long 
. Any luck with your endo figuring this out?
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First of all, I’m assuming you’re in auto mode, since that’s where most of these problems crop up. This pump is still as new to most endos as it is to us, so she/he may not know what some of its peculiarities are. Some of this stuff I tried to cover upthread, but to save time I’ll respond to a couple of things directly. Most important pertains to this:
In auto mode, the ISF setting is meaningless. Doesn’t pertain. Only functions in manual.
In auto, the only manually-adjustable parameters that the pump pays any attention to are: Carb Ratio (CR) and Active Insulin Time (AIT), both of which are under Options → Delivery Settings → Bolus Estimate Setup. The key thing to get through your head is that these things don’t mean exactly what it sounds like they mean. You want to think of AIT, not as “how long insulin actually remains active in my system by any empirical measure,” but “this is a dial I can turn to make the algorithm more aggressive toward lowering my BG.” In Auto, “basal” is called “microbolus” for a reason. It isn’t a steady rate but a series of little dynamically-determined blips, each one of which makes certain assumptions about what it has already delivered. So if it thinks the previous blip is going to last 4 hours, it’s going to be very conservative in figuring out the next blip it’s about to dole out. Decreasing that time gives it permission to deliver more insulin per blip. As you shorten it up you end up stacking your insulin, but really it’s kind of designed to do that; the only question is how much. So don’t think of it as “how long does it actually take insulin to clear,” but “how high do I want to turn this thing up.” They started me out at 3hrs, which was lower than my manual setting but nowhere near good enough for me on Auto. You definitely want to be incremental (obviously this stuff is dangerous, but then we all know that), but I ended up taking it all the way down to 2hrs, the minimum setting.
CR is a bit more subtle because normally you’d think it was only a factor in the Wizard figuring out meal boluses for you, but the algorithm definitely takes account of this setting even when you’re not consuming carbs–the “microbolus” concept is a factor here too. Exactly how it takes account of this is a bit more mysterious, but it definitely makes a difference. I ended up setting something like 5 different CRs throughout the day, with a particularly insane one starting at around 3am to get the thing to be more aggressive about getting ahead of my Dawn Phenomenon, which has always been a big problem. It’s also a bit mysterious because of the way the algorithm takes several days to integrate changes to these parameters with what it’s seeing from your sensor. So you have to be incremental with your changes and a bit patient waiting to see the results in order to avoid getting into trouble.
Hope that helps!
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Thanks! Yes, i read the whole thread. I’m aware of the AIT change being one of the most powerful (I already moved mine to 2.5hrs), though it’s true that I’m still flummoxed by the CR changes having an effect. My Dawn Phenomenon was actually fully fixed with no effort; it’s the highs that I’m hitting so hard. I’m already at a 1:6 and 1:8 CR for the day so I’m not sure how much I can adjust, but I guess there’s still some room (and I won’t have to feel quite as embarrassed given that it’s one of only two levers I have).
I’m definitely confused about the ISF here considering it does give me kind of random small amounts of insulin. I’m just so frustrated that my carb bolus is subtracted against my BG bolus, even when they’re at the same time. So frustrating. I guess I’ll lower AIT to 2.0 and maybe increase CR (i.e. decrease denominator).
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How easy/hard is it to change from auto-mode to manual-mode? Like if you are high - switch to manual-mode, take a bolus, and switch back to auto-mode. Would that be a pain?
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I considered that a few times, but the big issue was what effect it was going to have on the algorithm–whether you’d be “training” it to be less responsive on its own. This is kind of a subset of another quandary. Some people get around the DP problem by just switching into manual for overnight. I considered this, because my basal settings were handling mine just fine before I went over to auto. But at some point, if you’re flipping out of auto all the time to handle this stuff, it starts to be a question of what auto is actually doing for you.
I really came up against this about a week ago when my DP, which had been improving, suddenly veered the other direction again. I thought, hey, I could just do the overnight Manual Mode thing, but that raised the question about why turn auto back ON after that. Like, the whole theory is that this thing is supposed to be taking the burden off of you, but in effect that was just making it seem like it was taking the controls out of my hands without doing as good a job as I could do on my own.
It’s not that I’ve been doing so terribly. I’d guestimate my A1C in auto is running about 6.5-6.6, which for a lot of people would be absolutely thrilling. If you’ve been up in the 7s, 8s or worse, this thing is going to seem like a dream come true. But if you’ve been doing really well with a standard pump, A1Cs in the low-6/high-5 range–mine was a pretty steady 6.0 or 6.1–it’s just going to take a lot more effort in the form of finger-poking and parameter-tweaking and head-scratching to replicate those results with this system than you were having to exert before. So what exactly are you getting in return?
At any rate, I’m taking a break from it for now. I might give it another try after I’ve had some time off.
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I am confused by this. Wouldn’t you want it in auto at night when sleeping, and manual when you are awake? This seems the opposite of how I would envision the workaround - when you are awake you can bolus, but when you are asleep you just let it do its thing.
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Auto mode had a million ways of waking you up. Calibration failing, asking for a bg for no discernable reason, alarming that it’s either been suspended or at max for too long. That plus the fact that it’s really slow to adjust your bg gives a lot of disincentives.
Also, it’s actually a pain to switch and give a bolus. To get back, you have to give another bg right then, even if you just tested. And it throws up a million alarm screens before you get there. Not to mention that you’re breaking its training.
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