The bionic pancreas developed by a Boston University/Massachusetts General Hospital research team consists of a smartphone (above) hardwired to a continuous glucose monitor and two pumps (below) that deliver doses of insulin or glucagon every five minutes; ©Boston University Department of Biomedical Engineering
The latest version of a bionic pancreas device has been successfully tested in two five-day clinical trials – one in adults, the other in adolescents – that imposed minimal restrictions on patient activities.
The device controls blood sugar in patients with type 1 diabetes using doses of both insulin and the blood-sugar-raising hormone glucagon. "In both of these studies this device far exceeded our expectations in terms of its ability to regulate glucose, prevent hypoglycemia and automatically adapt to the very different needs of adults – some of whom were very insulin-sensitive – and adolescents, who typically need higher insulin doses," says Edward Damiano, PhD, of the BU Department of Biomedical Engineering, principal investigator of the project and senior author of the NEJM report. "There is no current standard-of-care therapy that could match the results we saw."
Firas El-Khatib, PhD, of the BU Department of Biomedical Engineering, adds, "One of the key virtues of this device is its ability to start controlling the blood sugar instantly, based only on the patient's weight, and continually adapt its decision making regarding insulin and glucagon dosing to handle a wide range of dosing requirements." El-Khatib co-designed the bionic pancreas device with Damiano and is co-lead author of the NEJM report with Steven Russell, MD, PhD, of the MGH Diabetes Unit.
Russell – who led the clinical trials– Damiano, and El-Khatib previously published a 2010 Science Translational Medicine report that described successful use of the first-generation system in controlling the blood sugar of adults for 27 hours. But that study took place in a controlled hospital inpatient environment where participants essentially stayed in bed for the whole period and ate prescribed meals. "The key element with the current version of this device is that it is wearable, allowing participants to stay in something close to their usual environments, exercise and eat whatever they want," says Russell.
Developing a device that could be tested safely in an outpatient environment presented several challenges, first among which was a control system that could adapt not only to the minute-by-minute changing needs of an individual, but also to the very different needs of adults and adolescents. The rapid growth and hormonal changes of adolescence produces insulin requirements that are two to three times greater than those of adults of the same body weight, Damiano explains. And even though the dosage needs of adults are more predictable, contracting an illness like a cold or upset stomach can dramatically change the need for insulin over a period of days to weeks.
Along with the software improvements that allow the device to adapt to widely varied individual dosage needs, the new version also relies on improved hardware, including a smartphone (iPhone 4S) capable of practical wireless communication with two pumps delivering doses of insulin and glucagon. Every five minutes the smartphone receives a blood sugar reading from an attached continuous glucose monitor, which it uses to calculate and administer a dose of either insulin or glucagon. The smartphone includes an application on which the patient enters information immediately before eating. But instead of the complex calculation patients typically do to estimate their carbohydrate intake, this app only asks whether the meal consumed will be breakfast, lunch, or dinner and whether the carbohydrate content will be typical, larger or smaller than usual.
Both of the studies compared data reflecting five days on the bionic pancreas system with five days of participants' usual care using their own insulin pumps. The adult trial enrolled 20 participants who lived at home and managed their own care during the usual-care period. While on the bionic pancreas, participants needed to stay within a three-square-mile area of downtown Boston, which enabled constant wireless monitoring of the blood sugar levels by study staff. They were accompanied by a study nurse 24 hours a day and slept in a hotel; but were otherwise free to do as they chose, including exercising at a gym and eating in restaurants.
The adolescent trial enrolled 32 participants, ages 12 to 20, attending a camp for youngsters with type 1 diabetes, who followed the same activity and meal schedule as other campers during both phases of the trial. They were closely monitored by study and camp staff and via wireless monitoring during their time on the bionic pancreas. Participants in both phases of both trials were alerted if blood sugar levels dropped into a range requiring carbohydrate administration, including during nighttime monitoring.
In both studies, the time on the bionic pancreas produced what Russell calls, "two results that almost never go together. Participants' average blood glucose went down while the incidents of low blood sugar also dropped. The fear of hypoglycemia can limit attempts to bring the average blood sugar into the range that dramatically reduces the risk of long-term complications, so it was remarkable that we saw both of these results at once. Both groups had quite good levels in the usual care arms – averages of 159 for both adults and adolescents – but the difference while they were on the bionic pancreas was dramatic, with average blood sugar levels of 133 for the adults and 142 for adolescents." Fewer instances of hypoglycemia on the bionic pancreas also reduced the need for carbohydrate doses to raise blood sugar.
MEDICA.de; Source: Massachusetts General Hospital