While the bihormonal system can help to prevent hypoglycemia, there are disadvantages to using glucagon. The primary disadvantage is that current formulations of glucagon are not stable beyond 8 h. This is why patients in the study had to change their glucagon pods every 8 h. In the future, new formulations of glucagon, currently under clinical trials testing, which are stable for multiple days is plan to use . In future studies, the next generation Dexcom sensors (G4 PLATINUM) with more reliable wireless interface can continue to use. And also, a fully wireless system that will have the mobile phone communicating directly with the sensors and the pumps without requiring the sensor receiver or the pump PDM to enable communication can develop.
Closed-loop control can lead to glucose levels ranging within the normal glycemic range of 70–180 mg/dL approximately 70% of the time. The system takes advantage of a secondary pump that can help to prevent hypoglycemia through the delivery of glucagon when a hypoglycemic event is pending. For the system, it is able to maintain subjects‟ glucose levels within the near-normal glycemic range for 72.5%. The system utilized two sensors which enabled continued automation when one sensor was missing. The purpose of having two sensors is primarily to help overcome the problems associated with sensor inaccuracy.
The attribute prevention of hypoglycemia to the use of the bihormonal system whereby glucagon leads to rapid glycogenolysis as the patient‟s glucose begins to drop and approach the target glucose. An additional disadvantage is that excessive glucagon delivery to a patient may lead to liver glycogen depletion. If liver glycogen depletion occurs, the patient‟s glucose will not increase and hypoglycemia could result. Furthermore, excessive glucagon administration can lead to side effects including hyperglycemia and nausea. The control algorithm limits glucagon delivery amounts as described in (10) None of the subjects experienced side effects of glucagon overexposure and a study using noninvasive imaging to estimate hepatic glycogen is underway to address the question of potential glycogen depletion resulting from repeated SC doses of glucagon. An additional limitation of our AP system is that it requires the patient to provide an estimate of carbohydrate intake into the system during meals. If a patient enters an incorrect amount, the algorithm will potentially deliver an incorrect amount of hormone in response.
The system utilized two sensors which enabled continued automation when one sensor was missing. The purpose of having two sensors is primarily to help overcome the problems associated with sensor inaccuracy. The setup required that both the Dexcom receivers and the Insulet PDM be hard-wired to a USB port, making disconnection during regular activities of daily living a common problem.
Lets conclude that the bihormonal APC algorithm presented here functioned well when the hardware was functional, especially in preventing hypoglycemia. Therefore the system is expected to perform well in an outpatient study once the hardware interconnections are made to be more robust.