mylife CamAPS FX (mmol/L)

Introduction to Closed Loop

A healthy pancreas releases insulin according to the body’s needs. As a result a normal, narrow range of blood glucose is maintained. In type 1 diabetes this function of the pancreas is lost, leading to the need to inject insulin to control blood glucose. By inserting a very thin catheter under the skin we can mimic the action of the pancreas by using an insulin pump to infuse the correct dosage of insulin for the body’s needs. A continuous glucose sensor, also known as continuous glucose monitor (CGM), measures glucose in the subcutaneous tissue allowing the calculation and delivery of insulin required in a continuous and uninterrupted fashion.

The continuous glucose sensor and the insulin pump are two of the three necessary components of a closed loop system also known as an artificial pancreas. The remaining component is a computer or a smart device running a closed loop algorithm that calculates the insulin dose based on the glucose sensor readings. Those three interlinked components form what we call a “closed loop”.

What is CamAPS FX?

CamAPS FX is an app that runs on an android phone. The app is designed to work with a pre-defined selection of commercially available insulin pumps and continuous glucose monitors.

The app also allows data upload to the cloud for data visualisation and remote monitoring.

Modes of Operation

The CamAPS FX app operates in one of two modes:

(1) Auto mode Off (open loop)
Auto mode Off is the mode of operation most familiar to current pump users. In this mode of operation, the pump operates at the pre-programmed basal profile, or as instructed by the user.

Auto mode Off is the default mode of operation on system start-up.

(2) Auto mode On (closed loop)
Auto mode or closed loop mode is the mode of operation where:

a) Insulin delivery is directed by the app replacing pre-programmed basal insulin delivery.
or
b) The ‘app’ is attempting to enter Auto mode but a condition is preventing it from doing so, for example, when CGM data become unavailable. The ‘attempting’ status continues until the condition preventing the start of Auto mode is resolved. When in ‘attempting’ mode, insulin infusion will revert to the pre-programmed basal rate after approximately 30 minutes.

SMS-based Remote Monitoring

The CamAPS FX app supports SMS-based remote monitoring during Auto mode On and Off. All app generated alarms and alerts will be sent via SMS message to up to five ‘Followers’.

How closed-loop work?

The CamAPS FX app uses a mathematical model of insulin action to determine insulin infusion leading to a target glucose of around 6mmol/L.

For the model of insulin action to operate correctly, information is needed at setup and then during the system operation. The body weight is used to approximate glucose and insulin concentrations within the body. The total daily dose of insulin is an initial indicator of insulin sensitivity, which is further refined by analysing continuous glucose monitor (CGM) data, previously administered insulin infusion and boluses, and meal intake.

Previous insulin infusion and boluses, together with CGM and meal data are used to update insulin sensitivity and other subject specific characteristics. The mathematical model then uses these characteristics together with information about active insulin and active meals to predict future glucose concentrations and to determine the optimum insulin infusion leading to the target glucose level.

In certain situations such as when CGM glucose is low or is decreasing fast, the control algorithm may further reduce insulin to reduce the risk of hypoglycaemia.

Instructions for use are available in electronic format at www.camdiab.com and via the app. PDF viewer is required to read the electronic instructions. For a paper copy of instructions, please contact [email protected].