# Closed loop system



## Tom1982 (Jan 11, 2022)

I’m a pump engineer (not insulin pumps unfortunately). To me a closed loop system is a pump that reacts automatically to a signal from a sensor. 
Is this effectively what a closed loop system is for insulin pumps too? 
Currently trying to suss out what our best option is for our 4 year old daughter.


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## Windy (Jan 11, 2022)

There's some information here on the Diabetes UK pages about it (they don't recommend DIY systems), with links to 4 commercial pumps at the bottom of the page.
But all this is well outside my knowledge, as I'm T2 on pills. Hopefully the more knowledgable forum members know!


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## Lily123 (Jan 11, 2022)

A closed loop system is where the pump will decrease or increase the amount of insulin depending on what the sensor tells it. The two closed loop systems I know of are the Tandem Tslim pump linked with a Dexcom and a Medtronic pump linked with a Guardian sensor


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## Inka (Jan 11, 2022)

The Dana RS can be looped too, either with its official loop that uses Dexcom, or with Open APS. Yes @Tom1982 a closed loop is as you described. You can also have an open loop, or switch the closed loop off at certain points eg at night.


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## Tom1982 (Jan 11, 2022)

Lily123 said:


> A closed loop system is where the pump will decrease or increase the amount of insulin depending on what the sensor tells it. The two closed loop systems I know of are the Tandem Tslim pump linked with a Dexcom and a Medtronic pump linked with a Guardian sensor


So out of curiosity, why doesn’t everyone want a closed loop system???


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## Inka (Jan 11, 2022)

Tom1982 said:


> So out of curiosity, why doesn’t everyone want a closed loop system???



Because hardly anyone gets Dexcom for free and most people can’t afford to pay for it.


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## Lily123 (Jan 11, 2022)

Tom1982 said:


> So out of curiosity, why doesn’t everyone want a closed loop system???


Like @Inka said. And the fact that most aren’t even offered a pump because the guidelines don’t address many issues of MDI


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## Tom1982 (Jan 11, 2022)

Inka said:


> Because hardly anyone gets Dexcom for free and most people can’t afford to pay for it.


Ahhh right. Is the Dexcom a monthly pay out?


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## Bruce Stephens (Jan 11, 2022)

Tom1982 said:


> Ahhh right. Is the Dexcom a monthly pay out?


Often, yes. And most of us aren't offered a pump. (Things are a bit different on both things if you're 4 or (more generally) under 12.)

There are proposed updates to the NICE guidelines which should open up CGMs (like Dexcom) much more broadly to people of all ages with Type 1, and there are trials on closed loop systems which everyone expects to be very positive, and with any luck NICE will give recommendations for them. I'm still not holding my breath, but I hope closed loops will be fairly common within ~5 years. It certainly feels like that's possible, and maybe then I'll be able to get one.


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## Lily123 (Jan 11, 2022)

Bruce Stephens said:


> Often, yes. And most of us aren't offered a pump. (Things are a bit different on both things if you're 4 or (more generally) under 12.)
> 
> There are proposed updates to the NICE guidelines which should open up CGMs (like Dexcom) much more broadly to people of all ages with Type 1, and there are trials on closed loop systems which everyone expects to be very positive, and with any luck NICE will give recommendations for them. I'm still not holding my breath, but I hope closed loops will be fairly common within ~5 years. It certainly feels like that's possible, and maybe then I'll be able to get one.


I’ve never really understood the under 12 bit and if your older but still not an adult you are counted as an adult in the guidelines it’s incredibly annoying


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## SB2015 (Jan 11, 2022)

The other thing with the closed loop is that the pump not only needs to react to the information from the sensor, it also needs to take account of the delay in action  time of the insulin you are using, as well as any active insulin you already have on board.  The pumps do this using an algorithm, whether they are in manual or in closed loop.

I have now used the closed loop for nearly a year, and would not want to go back.  However 8 do have to fund the sensors.  I am using a Medtronic 780 pump with their own sensors.


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## Inka (Jan 11, 2022)

Tom1982 said:


> Ahhh right. Is the Dexcom a monthly pay out?



They have various deals but it’s very roughly £160-180 per month if I remember correctly. No way could I afford that.

Bear in mind also that only a small percentage of people with Type 1 have a pump.


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## Bruce Stephens (Jan 11, 2022)

Lily123 said:


> I’ve never really understood the under 12 bit and if your older but still not an adult you are counted as an adult in the guidelines it’s incredibly annoying


I guess they want to draw a line somewhere, and while it's inevitably a bit arbitrary 12 feels to me like a plausible age to do it at.

My hope is that with falling costs in sensors and increased appreciation for the value of them and of pumps, maybe gradually there'll be less interest in limiting access to pumps and things for people over 12.


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## Tom1982 (Jan 11, 2022)

Inka said:


> They have various deals but it’s very roughly £160-180 per month if I remember correctly. No way could I afford that.
> 
> Bear in mind also that only a small percentage of people with Type 1 have a pump.


So in our case they are talking about various pumps that are available. If it wasn’t a closed loop type could we potentially make up the difference or are we completely on our own unless we go with what’s offered? I was trying to ask that today but they kept going on about reliability and so on.


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## Inka (Jan 11, 2022)

Tom1982 said:


> So in our case they are talking about various pumps that are available. If it wasn’t a closed loop type could we potentially make up the difference or are we completely on our own unless we go with what’s offered? I was trying to ask that today but they kept going on about reliability and so on.



Yes, you could make your own loop if you had an appropriate pump. The people I know who loop have bought the extras themselves but got their pump on the NHS.

I don’t think I’d loop with a young child though personally.


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## Lily123 (Jan 11, 2022)

Bruce Stephens said:


> I guess they want to draw a line somewhere, and while it's inevitably a bit arbitrary 12 feels to me like a plausible age to do it at.
> 
> My hope is that with falling costs in sensors and increased appreciation for the value of them and of pumps, maybe gradually there'll be less interest in limiting access to pumps and things for people over 12.


Hopefully pumps will become available to more people in the coming years


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## Pumper_Sue (Jan 11, 2022)

Tom1982 said:


> So out of curiosity, why doesn’t everyone want a closed loop system???


Personally I do not think the sensors are accurate enough and as I am sensitive to insulin I suspect I could be in big trouble using it.


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## Tom1982 (Jan 11, 2022)

Inka said:


> Yes, you could make your own loop if you had an appropriate pump. The people I know who loop have bought the extras themselves but got their pump on the NHS.
> 
> I don’t think I’d loop with a young child though personally.


Very interesting. Cheers for your input. I just assumed this was the way to go, never considered the merits of doing it another way. Just shows how little we know at the moment!


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## Inka (Jan 11, 2022)

Tom1982 said:


> Very interesting. Cheers for your input. I just assumed this was the way to go, never considered the merits of doing it another way. Just shows how little we know at the moment!



There’s no easy answer to Type 1 sadly. Yes, some things will make life easier, but it’s all a balance of what suits the individual, what they’re prepared to tolerate, how much mentally they want to invest.

What helps most is free - experience. Read lots, be patient and cautious always, and you’ll gradually get experience that is absolutely invaluable.


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## rebrascora (Jan 11, 2022)

Tom1982 said:


> So in our case they are talking about various pumps that are available. If it wasn’t a closed loop type could we potentially make up the difference or are we completely on our own unless we go with what’s offered? I was trying to ask that today but they kept going on about reliability and so on.


Not all pumps can be looped and your choice of pump will be limited to what your area offer, so a looped system may not be possible. 
You need a lot of support with pumps particularly initially and nursing staff are only trained on the ones available in their area, so short of moving to a different area when looped pumps are available, even if you have to self fund the sensors, might be necessary if you have your heart set on a looped system. As I understand it though, it is not a hands off system. You still need to carb count and bolus for food.


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## RTI (Jan 13, 2022)

Hi, 
a closed loop  is not a totally closed loop as you know it from your body (it is a semi-closed loop). You still need to give info to the pump how much and when you eat (carb-ratios, correction-ratio). It still need some work, but the system will learn in time (especially about your Basal-levels), it will help and improve your diabetes-comfort and improve your glucose-level futher and your diabetes control. The system reacts if your glucose is going into extreme levels(epecially too low over night, it will stop insulin delivery for some time).   But it is not the universal solution of the Diabetes, it is a big step forward for your diabetes securiy and comfort.

You may see more closed-loop system coming up in 2022. For example, there will be a Freestyle libre 3 sensor coming-up (hopefully 2022, as it is also available on the continent (EU). Omnipod (insulin pump) will put on the market (UK) a version (OMNIPOD 5), which is closed-loop capable with Dexcom or Freestyle Libre 3 and seems to be that quite some more (22-23) will be available on the market.

PS: I am waiting for it


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## everydayupsanddowns (Jan 13, 2022)

Yes that’s just what I was going to say @RTI 

The current hybrid closed loop systems (both commercial and DIY) offer a bit of a helping hand, and can significantly improve ‘time in range’ and hugely reduce the incidence of mild hypoglycaemia, but they still need quite a lot of user input and careful handling.

One of the limitations is that we are (as one speaker I saw presenting once commented) using the wrong insulin, with the wrong profile and delivering it in the wrong place. ’Proper’ insulin splurged out by the pancreas goes whooshing down the duct and starts working almost instantly (and stops working just as quickly!)

So pumps are a huge leap forward, and like @SB2015 I would really miss the functionality having lived with a sensor-augmented pump for the past 5 years, but you do have to estimate/count carbs… time your doses correctly… let it know if you are more active than usual or exercising… some also have different settings for sleeping.

The various algorithms need different user input, and part of effective use of the systems, in my experience, is working out what information it needs to work well for you, and when you need to consider overriding the automation (and when you are much better leaving it to do its thing!!)


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## RTI (Jan 13, 2022)

Pumper_Sue said:


> Personally I do not think the sensors are accurate enough and as I am sensitive to insulin I suspect I could be in big trouble using it.


The sensor maybe not as accurate as you would like it, but you may prefer to prick your fingers 30-40 times a day to get an accurate profile and may find out that the glucose-reading are also differing between test-stripes form different producer. 

Sensor-readings are still correct in a range of 5-15% and it maybe larger if your glucose level is changing fast due to sugar intake, etc.. But you learn in time that there is a time-delay and you may take sensor-readings at any time and at any place and as many times you want (50-60 times a day or more). 

With test-stripes you must look for a place for testing, carrying around a test-set, clean your finger and prick it, etc.... Especially at work this makes a huge difference to a sensor.

And the new generation of sensor are transfering the measurement every minute auotmatically to your reader or mobile and will give alarm if to high or to low. so you just need to take a look at your mobile what's going on, eventhough the values may differ sometimes by 0.1-1 mmol/l, but  it is a huge advantage and gives a so much more information about your glucose/food behaviour. 

I had type 1 ~40 years and went through all type from testing from urine-testing and blood-test-stripe with waiting times from 5mn to 2mn, later 1mn and today 10sec. 
I also hasitated to switch to sensor with the same argumentation as you have given.
But the step to a sensor 3 years a ago was a revelation and a huge step foward and I have learned in between of weeks and month more about my body and it's diabetic behaviour then what I thought to know already with my 40 years of experience.

Diabetes is not only a tablet which you take and everything is ok. You must accept that you have diabetes and may have to adapt and if you are doing it you may have a very good life also with diabetes.


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## Pumper_Sue (Jan 13, 2022)

RTI said:


> Sensor-readings are still correct in a range of 5-15% and it maybe larger if your glucose level is changing fast due to sugar intake, etc.. But you learn in time that there is a time-delay and you may take sensor-readings at any time and at any place and as many times you want (50-60 times a day or more).


I have used sensors for years, and no I do not have massive changes in my levels. I have had sensors that can be anything from 2 - 5 points out with some but not all sensors. So no I would not trust a sensor to bolus from.



RTI said:


> Diabetes is not only a tablet which you take and everything is ok. You must accept that you have diabetes and may have to adapt and if you are doing it you may have a very good life also with diabetes.


After almost 57 years with type 1 diabetes I think I have worked that out myself so please don't be so patronising.


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## trophywench (Jan 14, 2022)

Plus I would point out that Tom does not have diabetes - he is enquiring on behalf of his 4 yo child!


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## SB2015 (Jan 15, 2022)

Hi @RTI 

Let us know what you decide for your child.  I have met children in schools using pumps with and without sensors which have certainly made things a lot easier.  Others using MDI along with a Libre.  

Things are changing so quickly now and it is going to be interesting to see what becomes available.


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