Closed-loop (CL) therapy systems should be safe, efficacious, and easily manageable for type 1 diabetes mellitus patient use. For the first two clinical requirements, noninferiority and superiority criteria must be determined based on current conventional and intensive therapy outcomes. Current frequencies of hypoglycemia and diabetic ketoacidosis are reviewed and safety expectations for CL therapy systems are proposed. Glycosylated hemoglobin levels lower than current American Diabetes Association recommendations for different age groups are proposed as superiority criteria. Measures of glycemic variability are described and the recording of blood glucose levels as percentages within, above, and below a target range are suggested as reasonable alternatives to sophisticated statistical analyses. It is also suggested that Diabetes Quality of Life and Fear of Hypoglycemia surveys should be used to track psychobehavioral outcomes. Manageability requirements for safe and effective clinical management of CL systems are worth being underscored. The weakest part of the infusion system remains the catheter, which is exposed to variable and under-delivery incidents. Detection methods are needed to warn both the system and the patient about altered insulin delivery, including internal pressure and flow alarms. Glucose monitor sensor accuracy is another requirement; it includes the definition of conditions that lead to capillary glucose measurement, eventually followed by sensor recalibration or replacement. The crucial clinical requirement will be a thorough definition of the situations when the patient needs to move from CL to manual management of insulin delivery, or inversely can switch back to CL after a requested interruption. Instructions about these actions will constitute a major part of the education process of the patients before using CL systems and contribute to the manageability of these systems.
[Show abstract][Hide abstract] ABSTRACT: Pursuit of a closed-loop artificial pancreas that automatically controls the blood glucose of individuals with type 1 diabetes has intensified during the past six years. Here we discuss the recent progress and challenges in the major steps towards a closed-loop system. Continuous insulin infusion pumps have been widely available for over two decades, but "smart pump" technology has made the devices easier to use and more powerful. Continuous glucose monitoring (CGM) technology has improved and the devices are more widely available. A number of approaches are currently under study for fully closed-loop systems; most manipulate only insulin, while others manipulate insulin and glucagon. Algorithms include on-off (for prevention of overnight hypoglycemia), proportional-integral-derivative (PID), model predictive control (MPC) and fuzzy logic based learning control. Meals cause a major "disturbance" to blood glucose, and we discuss techniques that our group has developed to predict when a meal is likely to be consumed and its effect. We further examine both physiology and device-related challenges, including insulin infusion set failure and sensor signal attenuation. Finally, we discuss the next steps required to make a closed-loop artificial pancreas a commercial reality.
Annual Reviews in Control 12/2012; 36(2):255-266. DOI:10.1016/j.arcontrol.2012.09.007 · 2.52 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The availability of safe and reliable insulin pumps, fast-acting insulin analogues and devices allowing for continuous glucose measurement, has renewed the project of a continuous insulin infusion modulated at all times by blood glucose levels, i.e. in closed-loop. The recent research efforts focussed on the development of innovative algorithms in order to set a safe and efficient functional link between continuous glucose measurement and insulin infusion. Indeed, the combined delays of insulin action when subcutaneously infused and glucose estimation from measured glucose in the insterstitium represent the main concerns. The building of simulation platforms has boosted the creation of algorithms based upon the principle of model predictive control. The obtained validation of these control algorithms in hospital environment allows now the first ambulatory trials of wearable artificial pancreas models thanks to communication platforms which integrate the key-elements of the system.
Médecine des Maladies Métaboliques 12/2012; 6(6):490–494. DOI:10.1016/S1957-2557(12)70468-6
[Show abstract][Hide abstract] ABSTRACT: The “Dead-in-bed” syndrome refers to a few subjects with type 1 diabetes (T1D), very young and without forerunners sign except for a high frequency of severe hypoglycemia. These unexplained deaths are up to 10 times more frequent than in the paired non-diabetic population, the sequence could be due to hyperinsulinemia, hypoglycemia, hypokalemia, parallel activation of the sympathetic system and genetic predisposition to trigger severe and fatal rhythm and/or conduction disturbances. However severe nocturnal hypoglycemia is common and rarely causes such dramatic consequences. Hypoglycaemia causes QT prolongation systematically but whose magnitude varies among individuals, probably because of genetic predisposition as in long QT syndrome family. Autonomic neuropathy seems harmless and may even be protective by reducing sympathetic response. Prevention could go through a screening of subjects at risk among youth with T1D. Glucose sensors and closed loop pumps are the first to offer solutions to many of them..
Médecine des Maladies Métaboliques 03/2013; 7(2):178–184. DOI:10.1016/S1957-2557(13)70522-4
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