A newly developed computer program merges the operations of continuously implanted glucose sensors and insulin pumps in diabetics, bringing researchers closer to an artificial pancreas that could provide much better control of insulin levels, minimizing complications of the disease. The new results, published Friday in the medical journal Lancet, show that the computer can safely monitor glucose levels at night, a period when patients are at greatest risk of falling into potentially dangerous hypoglycemic episodes without realizing it. "This is an important step in diabetes control because it shows that, with this system, people can sleep safely with minimized risk of hypoglycemia," Dr. Eric Renard of Montpellier University Hospital in France wrote in an editorial accompanying the report.
Technology has been advancing in diabetes control in the last few years, and the biggest developments have been the adoption of continuous glucose monitors and insulin pumps. The monitors, embedded beneath the skin, provide regular updates on blood glucose levels, sounding an alert when they fall too low or climb too high. The pumps infuse a continuous low background level of insulin into the bloodstream, allowing the user to increase the amount after a meal or when otherwise necessary. An estimated 10% to 15% of the 3 million Americans with Type 1 diabetes now use one of the two devices or both. But researchers have been slow to successfully merge the two types of device because of problems ensuring that blood sugar levels do not get too high or too low.
One problem with the continuous infusion pumps is that sugar levels get too low during the night. That is a particular concern with children because their blood sugar levels can fluctuate widely in the best of times. Many concerned parents check their sleeping children several times during the night to ensure that their levels have not fallen too low, which can lead to dizziness, shakiness, seizures, coma and, in the worst cases, even death. "Without a doubt, the biggest worry for parents of kids with Type 1 diabetes is that their child will have a low-blood-sugar emergency during the night, when they are hard to identify," said Aaron Kowalski, director of the Juvenile Diabetes Research Foundation's Artificial Pancreas Project, which sponsored the new study.
Diabetes researcher Roman Hovorka of the University of Cambridge in England tested a new computer algorithm, or program, that responds to changing insulin levels to determine how much insulin a patient should receive. Researchers tested it in 17 children and adolescents who were hospitalized at night at Addenbrooke's Hospital in Cambridge for the study. The algorithm decided how much insulin the children should receive, but nurses adjusted the insulin pumps to the correct settings to ensure that no potentially dangerous mistakes were made. Some of the children received standard treatment, in which nurses administered insulin when a continuous monitor suggested it was necessary.
The researchers found that the children monitored by computer increased the amount of time their blood sugar levels were within target ranges from 39% to 52%. During the course of the trial, there were nine nighttime events of hypoglycemia among those receiving standard care, but none among those monitored by computer. The biggest effect occurred when the children exercised before going to bed: In that case, their sugar-level control increased from 48% to 78%.
"These studies show that automated systems not only can help people manage diabetes by maintaining good control, they will also improve quality of life for people with Type 1 diabetes and their families by lowering the risk of hypoglycemia," Hovorka said in a statement. He did not speculate about when a commercial device might be available.
All of the researchers have received money from companies that manufacture pumps and monitors, but those companies had no role in the study.
-- Thomas H. Maugh II
Photo: An implantable insulin pump manufactured by Medtronic. The pump must be refilled every three months. Credit: Medtronic