Automated Insulin Delivery System Nomenclature

Abstract

Dear Editor,

A number of novel technological advances have been made toward the development of closed-loop devices (i.e., artificial pancreas systems) that effectively treat and diminish the burden of diabetes.

We are submitting the following letter in support of the recent Biester et al. (March 2017, pp 173-182) publication in Diabetes Technology and Therapeutics entitled, Let the Algorithm Do the Work: Reduction of Hypoglycemia Using Sensor-Augmented Pump Therapy with Predictive Insulin Suspension (SmartGuard) in Pediatric Type 1 Diabetes Patients. This article reports on outcomes of individuals (1–21 years of age) with type 1 diabetes who used the MiniMed^™ 640G insulin pump system. We hope that this letter will provide readers additional information and clarity with respect to terminology used to describe insulin delivery devices that are sensor integrated versus sensor augmented.

We greatly appreciate your time and consideration of our submission and look forward to hearing from you.

Sincerely,

Ohad Cohen

In the past, all systems that automatically monitored glucose and delivered insulin based on monitored glucose levels were referred to as artificial pancreas devices. However, the term “artificial pancreas” has been an over-encompassing misnomer for insulin delivery systems whose algorithms may or may not deliver all requisite insulin. The Medtronic MiniMed 530G system (Medtronic, Northridge, CA) with the threshold suspend feature, approved by the Food and Drug Administration (FDA) for commercial use in the United States in 2013,¹ was considered an artificial pancreas device. Even today, the MiniMed 670G system, the first FDA-approved hybrid closed-loop (HCL) insulin delivery and continuous glucose monitoring (CGM) system,² is included on the FDA's Artificial Pancreas Device System website. The more specific HCL terminology delineates the MiniMed 670G system as a therapy that automatically increases, decreases, and suspends insulin delivery to target sensor glucose (SG) levels, while still requiring user input for meal boluses and correction boluses that address blood glucose (BG) >150 mg/dL. Harmonization and clarification of terminologies are required to differentiate systems that automate insulin delivery to different degrees, as we move toward the development of device systems that fully and automatically control all aspects of insulin delivery per a closed-loop algorithm.

The Medtronic MiniMed family of devices that automate insulin delivery is collectively referred to as sensor-integrated systems with SmartGuard^™ technology. In that regard, it is important to recognize that sensor-integrated pumps differ from sensor-augmented pumps. The difference between these terms is that a sensor-integrated pump takes action in response to the CGM sensor data, whereas a sensor-augmented pump merely displays CGM sensor data and does not take action (e.g., Medtronic MiniMed Paradigm^™ REAL-Time Revel™ System). Thus, display of sensor data is necessary but not sufficient for a system to be called sensor integrated. The functionality of MiniMed sensor-augmented pumps and sensor-integrated pump systems with SmartGuard technology is shown in Table 1 and includes the following features:

1. Low Glucose Suspend, Threshold Suspend, and Suspend on low as part of the MiniMed Paradigm Veo™, MiniMed 530G, and MiniMed 630G systems: these suspend insulin delivery for up to 2 h when SG levels reach a preset low limit. The preset basal rate automatically resumes after 2 h unless the user chooses to resume the preset basal rate manually.

2. Suspend on low as part of the MiniMed 640G and MiniMed 670G systems: this suspends insulin delivery for, at least, 30 min when SG levels reach a preset low limit unless the user chooses to resume the preset basal rate manually. After the minimum 30-min suspend time, the preset basal rate automatically resumes if certain criteria are met that suggest SG levels have recovered. The pump will also resume basal rate infusion if the autosuspension reaches the 2-h mark, regardless of SG levels at that time. In addition, the user can choose at any time to resume the preset basal rate manually.

3. Suspend before low in the MiniMed 640G and MiniMed 670G systems: this suspends insulin delivery before SG levels reach a preset low limit and resume preset basal insulin delivery when SG levels have recovered. Specifically, the pump suspends insulin delivery when SG levels are predicted to approach the preset low limit within 30 min. The pump will automatically resume preset basal insulin delivery within 30 min to 2 h if similar criteria as outlined in feature 2, mentioned previously, are met. In addition, the user can choose at any time to resume the preset basal rate manually.

4. Auto Mode (MiniMed 670G system): basal insulin delivery is fully automated based on the control algorithm to target 120 mg/dL. The control algorithm uses the SG value, its rate of change, the amount of active insulin, the algorithm-determined insulin sensitivity, and several safety features (e.g., the maximum amount of basal insulin for a given time period) to deliver a basal insulin dose every 5 min. The user can stop Auto Mode insulin delivery at any time. The user is still required to enter meal carbohydrates, accept bolus correction recommendations (if BG >150 mg/dL), and periodically calibrate the sensor.

Table 1.

Current Terms of Medtronic Insulin Delivery and Automated Insulin Delivery Systems and Their Technologies or Algorithms

Device type and function	Feature	General nomenclature	Medtronic-defined product
SAP Sensor data display on pump	Sensor data display on pump	SAP	MiniMed Paradigm REAL-Time Revel system
			MiniMed Paradigm REAL-Time 522/722
Sensor-integrated pump Sensor data display on pump and pump acts on sensor data	Suspends insulin at preset sensor threshold	LGS; TS; suspend on low; low suspend feature	SmartGuard LGS (described in feature 1)▪ MiniMed Paradigm Veo^a systemSmartGuard TS (described in feature 1)▪ MiniMed 530G^a systemSmartGuard Suspend on low (described in feature 1)▪ MiniMed 630G^a systemSmartGuard Suspend on low (described in feature 2)▪ MiniMed 640G^b system▪ MiniMed 670G^c systemSmartGuard Suspend before low▪ MiniMed 640G^b systemSmartGuard Auto Mode or HCL technology▪ MiniMed 670G^c system
	Suspends insulin in advance of preset sensor threshold	PLGM; PLGS
	Automatically adjusts basal insulin based on sensor data. User input required for meal boluses.	HCL system; HCL control
	Automatically delivers meal, correction, and basal insulin	Artificial pancreas; autonomous system for glycemic control; closed loop

Also operates in SAP mode.

Also operates in SAP mode with LGS, TS or Suspend on low feature.

Also operates in SAP mode with LGS, TS, or Suspend on low feature and the PLGM/PLGS feature.

HCL, hybrid closed loop; LGS, low-glucose suspend; PLGM, predictive low-glucose management; PLGS, predictive low-glucose suspend or suspension; SAP, sensor-augmented pump; TS, threshold suspend.

We hope that this letter will assist in the understanding of the emerging terminology derived from the introduction of novel automation in insulin delivery for the treatment of patients with diabetes.

Product Disclosure

The MiniMed 640G system is only available in select jurisdictions outside the United States. The MiniMed 530G, 630G, and 670G systems are commercially available in the United States, require a prescription, and have different indications, components, warnings, and contraindications associated with them. For more details, please see (www.medtronicdiabetes.com/important-safety-information).

References

Food and Drug Administration, Center for Devices and Radiological Health. MiniMed 530G System (P120010) approval letter, September 26, 2013. www.accessdata.fda.gov/cdrh_docs/pdf12/p120010a.pdf (accessed February 14, 2017 ).

Food and Drug Administration, Center for Devices and Radiological Health. MiniMed 670G System (P160017) approval letter, September 28, 2016. www.accessdata.fda.gov/cdrh_docs/pdf16/P160017a.pdf (accessed February 14, 2017 ).