Technologies in the management of type 1 diabetes

Technology is changing the way that people with type 1 diabetes are monitoring and managing their blood glucose levels

Diabetes technologies have transformed management options in type 1 diabetes. The most notable innovations include the commercialisation of insulin pumps, advancements in glucose monitoring and the capacity for these technologies to interact. New technologies offer enhanced flexibility in insulin delivery and opportunities to improve glucose levels and enhance quality of life. Recognising these benefits, the uptake of advanced technologies in Australians with type 1 diabetes has increased. In 2018–2019, 41% of children and 26% of adults attending hospital diabetes clinics managed their type 1 diabetes with insulin pumps, and 55% of children and 13% of adults newly commenced continuous glucose monitoring (CGM).1 In this article, we provide a guide to current diabetes technologies available in Australia, describe their benefits and discuss important factors in assessing an individual’s suitability.

Continuous glucose monitoring

Accurate and accessible glucose monitoring is key to effective diabetes management. Finger‐prick testing of capillary blood for self‐monitoring of blood glucose (SMBG) became commercially available in the 1980s, and CGM since 1999. CGM is distinguished from SMBG by the measurement of glucose concentration within interstitial fluid by a small subcutaneous glucose‐sensing electrode. Data are transmitted to a receiving device (eg, insulin pump or smartphone) and converted into a continuous graphic display. Interstitial glucose concentrations correlate with plasma glucose, albeit with an average 7–8 minute time lag for equilibration of glucose between blood and the interstitial compartment. This delay is exaggerated at times of rapidly changing glucose.

CGM systems come in different forms, with the main distinguishing features being the capacity to alert users and/or carers to high and/or low blood glucose levels set to individual preference. Various systems are available (Box 1).2,3 Product selection depends on the desirability of alarm functions, ease of sensor application, need for finger‐prick calibration, cost, and connectivity of the device to existing technologies (insulin pumps, Apple v Android systems).

Modern CGM systems are reliable. Their performance is assessed by the mean absolute relative difference, an accuracy metric expressed as the percentage difference relative to a reference glucose concentration. CGM devices with a mean absolute relative difference < 10% are appropriate for treatment decisions.2,4 To optimise sensor performance, SMBG testing is still required to calibrate a number of real‐time CGM devices, yet devices are increasingly reliable such that newer factory calibrated devices no longer require user calibrations5 — a welcome feature for convenience and reduced finger‐prick burden.

CGM offers several benefits to users, including on‐demand glucose testing, trend arrows, alarm functions and easy detection of out‐of‐range glucose levels. For clinicians, CGM offers additional data beyond glycated haemoglobin (HbA_1c) measurements. HbA_1c measurements are point estimates of haemoglobin glycation over 3 months, whereas CGM displays day‐to‐day glucose variability that often challenges people with type 1 diabetes. Consensus statements have attempted to harmonise the various commercially available CGM systems into a common reporting method to aid comparison between devices and also provide clinicians and users with more clinically meaningful data and targets (Box 2).2,6,7

Clinical trials provide evidence that CGM use may improve glycaemia in type 1 diabetes. A recent meta‐analysis of 15 randomised controlled trials comparing CGM with standard care (usually SMBG) in people with either type 1 or type 2 diabetes over 12–36 weeks found that CGM was associated with a slight reduction in HbA_1c levels (weighted mean difference, − 0.17%), and increased time in range (TIR; 71 minutes/day).8 Added up over a year the benefit equates to an additional 18 days of TIR. The effect on TIR was independent of diabetes type, or method of insulin delivery (insulin pump v needle injections). Overall, studies favour CGM to improve glucose variability (optimal coefficient of variation in diabetes management, 34%; coefficient of variation reduced by 3.0–6.7%) and reduce hypoglycaemia (0.4–1.2 hours reduction in time spent with glucose levels < 3.9 mmol/L) compared with SMBG.2

The benefits of CGM and flash glucose monitoring for type 1 diabetes management have been recognised by the Australian Government, which first pledged $54 million in 2016 to fully subsidise CGM in people under 21 years of age. In 2019, a further $100 million in subsidies was added. Eligibility criteria were again expanded in March 2020 (Box 3).9

Insulin pumps

An insulin pump delivers short‐acting insulin continuously via a cannula self‐inserted into subcutaneous tissue. In the 1970s, the first insulin pumps were large and bulky and delivered a single basal rate of insulin. Modern pumps are more discrete, the size of a pager.

An insulin pump set‐up includes two major components (Box 4):

• Insulin pump — case with display, battery and an insulin reservoir connected to a plunger that controls the passage of insulin into the line tubing. The insulin pump is programmed to deliver continuous quick‐acting insulin in equal aliquots (0.01–0.025 mL) across an hour depending on the pre‐set rate to replicate basal insulin. Programmed rates can be customised to vary across a 24‐hour period, distinguishing delivery from long‐acting insulin delivered at an inflexible basal rate. The user must initiate bolus doses for meals or for correction of an elevated glucose reading, but pre‐programmed settings provide dose calculations (insulin‐to-carbohydrate ratio for meals, and insulin sensitivity factor for correction doses).
• Line tubing and infusion set — up to 60 cm of thin plastic tubing connects the insulin reservoir to a subcutaneous teflon cannula (tubeless insulin patch pumps with variable hourly rates are not currently available in Australia).
• Potential benefits of insulin pumps include:
  1. ►  Flexibility in dosing — useful for extreme insulin sensitivity, erratic schedules, more convenient and frequent bolusing, to accommodate exercise, or to manage the dawn phenomenon (increased insulin requirements in the early morning period due to counter‐regulatory hormone secretion).
  2. ►  Bolus calculation capacity.
  3. ►  Less frequent insertion events (about every 3 days) — favourable for individuals with needle phobia.
  4. ►  Insulin delivery and glucose data can be generated electronically and remotely for review.

As only quick‐acting insulin is used in insulin pumps, insulin deficiency (leading to possible diabetic ketoacidosis) may occur within 2–3 hours of discontinuation of the insulin pump, or in the event of set occlusion. Set occlusion is one of the leading causes of ketoacidosis in insulin pump‐treated individuals but is rapidly corrected with recommencement of insulin in the absence of intercurrent infection (Box 5). However, insulin pump use has not resulted in the increased diabetic ketoacidosis events anticipated when first introduced, aided by appropriate education.10

There are out‐of‐pocket costs, especially for individuals without private health insurance, and running costs are higher than with insulin injection. Wearing an externally attached device to the body 24 hours a day is a deterrent to some, but a convenience for others who dislike carrying needle tips and insulin pens.

Insulin pumps can be used either as a stand‐alone device or in conjunction with CGM sensors (Box 6). Sensor‐augmented insulin pumps have the added benefits of suspended insulin delivery for predicted low glucose (predictive low glucose suspend), or at the threshold of hypoglycaemia (low glucose suspend) to reduce the frequency and duration of hypoglycaemia. In a study of individuals with documented nocturnal hypoglycaemia, those randomised to insulin pumps with low glucose suspend function for 3 months had 32% less frequent hypoglycaemia than without suspend function.11 Other trials have also demonstrated reduced time in hypoglycaemia without increase in time in hyperglycaemia.12

The latest insulin pump systems (hybrid closed loop; HCL) can provide a further degree of automation of insulin delivery. HCL pumps provide real‐time adjustment of insulin delivery in response to ambient glucose levels detected by a CGM sensor, via an inbuilt control algorithm. The user is still required to manually deliver boluses for meals or adjust insulin for exercise. A recent study comparing HCL to sensor‐augmented insulin pump therapy reported improved TIR during daytime hours as well as overnight, and a small reduction in time in hypoglycaemia over 6 months.13 There is currently only one registered HCL insulin pump in Australia. Future technologies may provide further integration of CGM and insulin pump devices via phone‐based applications.

Tailoring treatments to individual needs

The optimal approach for the management of type 1 diabetes depends on individual and practical considerations. Initiation of insulin pump therapy requires extended consultation to discuss device selection and cannula insertion technique, and review carbohydrate counting and troubleshooting (including diabetic ketoacidosis risk mitigation). It also requires a multidisciplinary approach involving an endocrinologist, credentialled diabetes educator and dietitian.14 In concert with the individual with diabetes, factors to discuss include:

• the need for alerts and alarms: presence of hypoglycaemia unawareness and susceptibility to alarm fatigue;
• affordability and eligibility for CGM supplied under the National Diabetes Services Scheme (Box 3);
• access to training and education;
• customisation of glucose targets for pregnancy, age and comorbidities;
• ability to use software to upload data and share reports with health professionals; and
• allergies to cannula or CGM site adhesives.

Conclusion

Diabetes technologies are being increasingly adopted by people with type 1 diabetes, and clinicians should familiarise themselves with the spectrum of devices. These advancements offer potential benefits for people with diabetes, although prescribing these devices requires evaluation of cost and benefit for the individual. Human factors are the main determinant of success and satisfaction, highlighting the importance of consideration of the needs of the individual.

Box 4 – Major components of insulin pump and continuous glucose monitoring (CGM) set‐up

---

 

Box 6 – Options for insulin delivery and glucose monitoring

---

CGM = continuous glucose monitoring; HCL = hybrid closed loop; MDI = multiple daily injections; PLGS = predictive low glucose suspend; SMBG = self‐monitoring of blood glucose.