Context: I am a type 1 diabetic. I have a CGM, but for various reasons use multiple daily injections rather than an insulin pump; however, I’m familiar with how insulin pumps work.
A major problem with a closed-loop CGM-pump system is data quality from the CGM. My CGM (Dexcom G6) has ~15 minutes of lag (because it reads interstitial fluid, not blood). This is the first generation of Dexcom that doesn’t require calibrations from fingersticks, but I’ve occasionally had CGM readings that felt way off and needed to calibrate anyway. Accuracy and noisiness vary from sensor to sensor (they last 10 days, officially; people have figured out how to “restart” them, but I’ve found often the noisiness goes up towards the end of the 10 days anyway), probably due to placement. It also only produces a reading every 5 minutes, probably partly to save battery but maybe also because more than that would be false precision anyway. And low blood sugar can be lethal rather quickly (by killing neurons, or by messing up neural function enough that you get into a car accident if you’re driving), so these issues mean caution is needed when using CGM readings to choose insulin dosing.
I’d think of connecting that to an insulin pump using a control system as more similar to Tesla Autopilot than to a Level 5 autonomous car. It’s sort of in the uncanny valley where the way it works is tempting you to just ignore it, but you actually can’t. I certainly don’t mean that these problems are impossible to overcome, and in fact “hybrid” closed loop systems, which still require manual intervention from time to time, are starting to become commercially available, and there are also DIY systems. (Type 1 diabetics vary in how much they geek out about managing it; I think I’m somewhere in the middle in terms of absolute geekiness, meaning, I would guess, 95th+ percentile relative to the relevant population.) But I think there are pretty strong reasons people don’t look at “well, just connect a 2022 off-the-shelf CGM, 2022 off-the-shelf insulin pump, and some software” as a viable fully closed loop for managing blood sugar for type 1 diabetics.
It’s been years since I’ve talked to anyone working on this technology, but IIRC one of the issues was that in principle you could prevent the lag from leading to bad data that kills you if the pump could also provide glucagon, but there was no way to make glucagon shelf-stable enough to have in a pump. Apparently that changed as of 2019/2020, or is in the process of changing, so maybe someone will make a pump with both.
I mean, just lag, yes, but there’s also plain old incorrect readings. But yes, it would be cool to have a system that incorporated glucagon. Though, diabetics’ body still produce glucagon AFAIK, so it’d really be better to just have something that senses glucose and releases insulin the same way a working pancreas would.
Context: I am a type 1 diabetic. I have a CGM, but for various reasons use multiple daily injections rather than an insulin pump; however, I’m familiar with how insulin pumps work.
A major problem with a closed-loop CGM-pump system is data quality from the CGM. My CGM (Dexcom G6) has ~15 minutes of lag (because it reads interstitial fluid, not blood). This is the first generation of Dexcom that doesn’t require calibrations from fingersticks, but I’ve occasionally had CGM readings that felt way off and needed to calibrate anyway. Accuracy and noisiness vary from sensor to sensor (they last 10 days, officially; people have figured out how to “restart” them, but I’ve found often the noisiness goes up towards the end of the 10 days anyway), probably due to placement. It also only produces a reading every 5 minutes, probably partly to save battery but maybe also because more than that would be false precision anyway. And low blood sugar can be lethal rather quickly (by killing neurons, or by messing up neural function enough that you get into a car accident if you’re driving), so these issues mean caution is needed when using CGM readings to choose insulin dosing.
I’d think of connecting that to an insulin pump using a control system as more similar to Tesla Autopilot than to a Level 5 autonomous car. It’s sort of in the uncanny valley where the way it works is tempting you to just ignore it, but you actually can’t. I certainly don’t mean that these problems are impossible to overcome, and in fact “hybrid” closed loop systems, which still require manual intervention from time to time, are starting to become commercially available, and there are also DIY systems. (Type 1 diabetics vary in how much they geek out about managing it; I think I’m somewhere in the middle in terms of absolute geekiness, meaning, I would guess, 95th+ percentile relative to the relevant population.) But I think there are pretty strong reasons people don’t look at “well, just connect a 2022 off-the-shelf CGM, 2022 off-the-shelf insulin pump, and some software” as a viable fully closed loop for managing blood sugar for type 1 diabetics.
It’s been years since I’ve talked to anyone working on this technology, but IIRC one of the issues was that in principle you could prevent the lag from leading to bad data that kills you if the pump could also provide glucagon, but there was no way to make glucagon shelf-stable enough to have in a pump. Apparently that changed as of 2019/2020, or is in the process of changing, so maybe someone will make a pump with both.
I mean, just lag, yes, but there’s also plain old incorrect readings. But yes, it would be cool to have a system that incorporated glucagon. Though, diabetics’ body still produce glucagon AFAIK, so it’d really be better to just have something that senses glucose and releases insulin the same way a working pancreas would.