This process started out simply and built up to the closed-loop technologies we know today, like the MiniMed 780G. However, in order to get there, the company needed engineers with a background in control systems.
Lintereur, the company’s chief engineer for MiniMed 670G and MiniMed 780G system, says those who study biomedical engineering don’t tend to gain that knowledge or study automatic control systems, or “control theory.” Typically, that’s reserved for other forms of engineering, including aerospace, which was the field Medtronic recruited him from.
Before Medtronic, Lintereur worked with a space company called Hughes Space Communications, developing pointing control systems for satellites. He wound up at NASA’s Armstrong Flight Research Center, designing flight control systems for experimental aircraft.
A career in medtech never even registered on Lintereur’s radar, he told Drug Delivery Business News. However, his move to Medtronic led to significant advancements in the company’s insulin delivery technology, as he played a significant role in the development of the company’s two latest pumps.
“It was that background and control system development that made me attractive to Medtronic as they started to develop this umbrella of technologies you might describe as artificial pancreas systems or automated insulin delivery systems,” Lintereur said. “So, I was able to apply my knowledge in that particular area of technology to insulin delivery systems and I haven’t looked back since.”
The steps Medtronic took toward a closed-loop system
MiniMed 670G marked the first step toward a hybrid closed-loop system for Medtronic. The hybrid aspect indicates that part of the insulin delivery is automated and part is manual.
With insulin delivery, patients receive basal insulin correction doses, bolus doses and meal boluses. Lintereur said that the company designed 670G to automate one of three with the basal insulin, leaving the boluses to the user. The idea there, particularly with mealtime boluses, was that the bolus estimations needed to be better.
“If the patient doesn’t get their meal bolus just right — and they rarely do — it’s difficult to estimate how much insulin you need,” he said. “The correction bolus can help compensate for that by giving additional boluses to help work on that meal for the patient.”
With 780G, Medtronic took another step forward, automating the basal and the correction boluses. If a user ate more than they anticipated or didn’t know how many carbohydrates were in their meal, or even if they forgot to bolus altogether, MiniMed 780G can introduce automatic correction boluses to compensate.
“Giving [patients] the automated correction boluses can help them get back to their target glucose faster than they would ever be able to do if they’re trying to do correction boluses by themselves,” Lintereur explained. “That was a key innovation.”
The latest-generation system also introduced glucose target options for patients, offering a lower target setpoint option. With 670G, patients had a one-size-fits-all target of 120 milligrams per deciliter. Now, with 780G, they can go as far down as 100 milligrams per deciliter, which is close to normal fasting glucose, Lintereur said.
“We had to re-optimize the system to work its best at that lower setpoint without the risk of hypoglycemia,” he said. “Then we offered a choice, recommending that they use 100 [milligrams per deciliter] but offering options at 110 and 120 if the doctor or patient feels more comfortable at a different level.”
Rebalancing the user experience
Lintereur said that a key factor in designing closed-loop technology is ensuring a smooth user experience but also ensuring safe and effective treatment.
“You have to strike a balance,” he said. “You can make this system extremely easy to use and as hands-off as possible, but you might have to sacrifice on the therapy.”
With 670G, Medtronic mostly struck a balance on safety, introducing extra alerts. However, those added alerts created extra, sometimes unnecessary, interruptions.
The company focused heavily on a better balance in that regard with 780G, using data from the 670G experience to reconsider where it drew its safety boundaries.
“We found that, by letting the system work longer without interrupting the patient, that was actually safer than alerting the patient and exiting them to their manual program,” Linteruer said. “Now that we have that data, we’re able to recalibrate all of the alerts within the whole alert design and safety design on the 780G to make a very, very improved user experience.”
The future of closed-loop systems
It’s clear to Lintereur that the future of insulin delivery includes an entirely closed-loop system.
“We’re obviously marching to a fully automated system,” he said. “The meal bolus is the last [mode of delivery], and we’re trying to find ways to automate that as well.”
Lintereur and Medtronic expect a shift in emphasis when it comes to automated insulin delivery. He explained that, right now, there’s possibly too much focus on hypoglycemia, or low blood sugar. But, with the introduction of the first- and second-generation closed-loop systems, patients can contain their hypoglycemia.
Now, Medtronic wants to focus more on hyperglycemia—high blood sugar—which can harm patients over days, months and years, he said. Potential effects include harm to cognitive development and performance, according to Lintereur.
Some of the technologies introduced in MiniMed 780G focus directly on hyperglycemia. Automatic correction boluses directly tie to the effort to reduce that, especially if a user forgets a bolus or fails to bolus correctly.
“This is our first attempt to really focus on this,” he said. “Our hope is that the broader industry will also start focusing more on hyperglycemia.”
