In people without diabetes, pancreatic islet cells detect glucose in the blood, and release insulin or glycogen to keep the glucose level in a safe range.
All people with type 1 diabetes use a treatment ‘loop’ to mimic this function the best we can – at present this involves:
- a pump or insulin pen (for insulin delivery)
- a blood glucose monitor and maybe CGM (for glucose level assessment), and
- our brains and fingers to calculate the dose required and deliver it to complete the loop
‘Closing the loop’ means making it happen automatically. This means a calculator or ‘algorithm’ is needed to replace our brains and fingers. The algorithm adjusts the basal (background) insulin every few minutes as necessary, to keep the glucose within a target range. At mealtimes, the user counts their carbohydrate and keys it in to the algorithm, which then decides how much insulin is required and sends an instruction to a pump to deliver the dose. This is called an artificial pancreas or closed-loop.
This technology has progressed in the last 10 years:
first came an insulin pump with low glucose suspend when CGM detects hypoglycaemia,
next there was predictive low glucose suspend when CGM detects glucose is falling towards hypoglycaemia,
current systems available are called hybrid closed loop – predictive high and low minimiser work alongside an automated basal rate (though some systems require a programmed basal rate as a starting point) but meal-time boluses must be programmed manually,
in the future we look forward to having fully automated closed loop with insulin only – needs no programming by the user,
and eventually fully automated closed loop with insulin and glucagon.
Where are we now?
Current commercial systems are called hybrid closed loop – predictive high and low minimisers work alongside an automated basal rate (though some systems require the user to programme a basal rate as a starting point) but meal-time boluses must be programmed manually.
People who follow a very low carbohydrate diet have been able to operate hybrid closed loop systems without meal-time input.
Systems available in the UK:
CamAPS FX hybrid closed loop uses a DANA insulin pump and Dexcom CGM. (This system comes from JDRF-funded research at Addenbrookes). Licenced for those aged 1+
Medtronic 670G + Guardian sensors hybrid closed loop uses Medtronic insulin pump and sensors. This system adjusts the basal rate to minimise predicted highs or and low glucose. Licenced for those aged 7+
Medtronic 780G + Guardian sensors hybrid closed loop uses Medtronic insulin pump and sensors, and minimises high and low glucose by adjusting the basal rate and delivering correction boluses. Licenced for those aged 7+
Control IQ hybrid closed loop uses Tandem t:slim insulin pump and Dexcom CGM. Licenced for those aged 4+
Earlier generations / systems that are less automated:
Medtronic 640G + Enlite or Guardian sensors with predictive low glucose suspend
Medtrum A7+ + Medtrum sensor has predictive low glucose suspend
Basal IQ has predictive low glucose suspend and uses Tandem t:slim X2 insulin pump and Dexcom CGM.
Predictive low glucose suspend will temporarily turn off the delivery of insulin when the sensor detects that the glucose level is likely to dip into a hypo, therefore preventing the hypo from happening or minimising it’s severity.
High glucose minimiser will activate when the sensor detects that the glucose level is likely to rise above the target. This may be by a temporary basal rate increae alone, small correction boluses, or a combination of both.
Can I get a closed-loop system on the NHS?
At present, in order to get a fully funded closed-loop system on the NHS, you will need to meet criteria for both pump funding and for CGM funding (see “Useful information” below). However, meeting criteria for CGM funding doesn’t necessarily mean it will be granted to you and CGM is not yet routinely funded.
If you can get a pump funded but can’t get funding for CGM, it is possible to ‘top up’ the system by paying for the CGM yourself.
NICE is currently appraising hybrid closed loops systems. The result is expected to be published in April 2022.
Useful information until then
For information on systems in development or systems that are not yet available in the UK, watch: