Getting Closer to a Reliable Artificial Human Pancreas

Despite the many glucose monitoring and insulin delivery devices that are available, many diabetics who use them remain uncontrolled and experience hypoglycemia. Researchers dream of the day that drug-device combinations will track diabetics' glucose levels and deliver appropriate insulin dose.

Experimental sensory-augmented pumps (SAPs) combine continuous glucose monitors (CGM) with insulin pumps, creating in essence an artificial pancreas. The October 2015 issue of Expert Opinion on Drug Delivery includes a review article that discusses the current state of the art.

The most basic form of SAPs--threshold suspension pump--is used to decrease hypoglycemia. When the CGM detects a glucose level below the threshold, it suspends basal insulin infusion. This SAP has the ability to stop or resume the insulin infusion, but not to change the basal rate.

More sophisticated SAPs that employ algorithms are called closed-loop (CL) artificial pancreases. They adjust insulin infusion rates according to the patient's glucose levels. Their real benefit is consistent nocturnal glucose monitoring, and one study showed a 10% reduction in average blood glucose and a 68% reduction in hypoglycemic episodes in patients who used CL devices. Another study looked at the CL system during the day and night and showed significant improvement in patients' time spent in target glucose ranges.

A bihormonal system is also in development. It infuses insulin and glucagon via separate algorithms and pumps. Its benefit is lower average glucose levels with less risk of hypoglycemia in adults.

According to some experts, a substantial amount of research is still needed, mainly on the CGM pump's reliability. These devices have a large variation in accuracy, with 5% of the readings being inaccurate by more than 50% of the actual value. Additionally, signaling can be lost leaving the patient at risk for inappropriate suspension of insulin.

Experts state the delay and variability in absorption of subcutaneous insulin is a potential pitfall. Additionally, insulin sensitivity often changes in response to the patients’ exercise, stress level, puberty and other illnesses.

Undoubtedly, clinicians and patients will be more likely to consider practical devices. Size, weight, battery life and screen display will play a role in these systems clinical uptake. Furthermore, third-party payment will likely be an issue.