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 glucose assessment is communicated 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.
Research by JDRF has identified 6 key steps:
- an insulin pump with low glucose suspend when CGM detects hypoglycaemia
- predictive low glucose suspend when CGM detects glucose is falling towards hypoglycaemia
- predictive low & high glucose minimiser
- hybrid closed loop – basal rate is automated but meal-time boluses must be programmed manually
- fully automated closed loop with insulin only – needs no programming by the user
- fully automated closed loop with insulin and glucagon
Where are we now?
Step 1 was achieved with the Medtronic Veo and Enlite sensors. The Veo can be accessed by people who meet NICE criteria for insulin pump therapy. CGM is not yet routinely funded.
Step 2 is where the Medtronic 640G with sensors fits.
Step 3 is where unregulated, DIY artificial pancreas systems fit in – with a well-tuned basal rate they can help users spend more time within the optimal glucose range.
Step 4 is now available, with CamAPS FX and with Medtronic 670G and 780G systems. This is known as hybrid closed-loop.
(Step 5 is currently in limited in-home research trials here in the UK and around the world.)
Systems available in the UK:
CamAPS FX with automated basal rate and predictive low & high glucose minimiser (the result of JDRF-funded research at Addenbrookes)
Medtronic Veo + Enlite sensors with low glucose suspend
Medtronic 640G + Enlite or Guardian sensors with predictive low glucose suspend
Medtronic 670G + Guardian sensors with automated basal rate and predictive low & high glucose minimiser via basal rate
Medtronic 780G + Guardian sensors with automated basal rate and predictive low & high glucose minimiser via basal rate & correction boluses
Medtrum A6 + Medtrum sensor has predictive low glucose suspend
Tandem t:slim X2 has predictive low glucose suspend with Basal IQ and automated basal rate + predictive low & high glucose minimiser with Control IQ (being rolled out now)
Low glucose suspend will temporarily turn off the delivery of insulin if the sensor detects a hypo and the user does not respond to the alarms, for example if they are asleep.
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 temporarily increase the basal rate when the sensor detects that the glucose level is likely to rise above the target. This may be by a temporary basal rate alone, small correction boluses, or a combination of both.
Also in development
23 June 2015 Insulin Nation article about Bigfoot Biomedical
Imperial College Hospital b.iap (bio inspired artificial pancreas)
Addenbrooke’s Hospital, Cambridge (Dr Roman Hovorka) funded by JDRF