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Open Loop

Open Loop Introduction

Open Loop is the best place to start with Loop.

  • Become familiar with Loop by watching it operate with Closed Loop disabled.
  • Take it slow and safe to become a successful Looper.

Practice with Simulators

You can build Loop without connecting it to any hardware.

  • You can use your phone, a partner's phone or a simulated phone on the computer
  • You can practice with a simulated CGM and / or a simulated pump.
  • You can use Dexcom Share or Nightscout as a CGM to follow your own glucose.
  • You can "dose" the simulated pump and your real pump at the same time and watch the glucose predictions.

Loop 2 - Open Loop

Loop 2 SAFETY WARNING

When you are operating in Open Loop mode, Loop 2.2.x (or FreeAPS) offers recommendations for insulin delivery adjustment and displays them on the HUD.

  • If you tap on the recommendation line, Loop applies that recommendation without asking for confirmation
  • This is true for temp basal and automatic bolus
  • To protect against accidental command of increased or decreased insulin dosing, make sure your phone is locked when not in use

Glucose Prediction

Pay attention to the prediction in the Glucose Chart Loop 3 / Loop 2. Practice with the user interface while you manually control your insulin delivery. Compare the recommended insulin after entering carbs for a familiar meal. If you do not understand the predictions or recommendations, do not enable Closed Loop. You may need to adjust settings or learn more about how the app works. Loop tries to keep predicted glucose in the Correction Range and, more importantly, above your Glucose Safety Limit (suspend threshold in Loop 2.2.x).

There's a lot to learn and understand. New loopers may need to adjust the following Therapy Settings, typically in this order:

  1. Basal Rates
  2. Insulin Sensitivity Factor (ISF)
  3. Carb Ratios (CR)

Using an algorithm that updates glucose predictions and adjusts insulin delivery every 5 minutes requires accurate settings. Entering carbs and absorption time is a new skill that takes time to master.

Eventual Glucose

Watch the eventual glucose, current glucose and prediction curve in the Glucose Chart Loop 3 / Loop 2 to understand Loop recommendations for insulin delivery adjustment. Loop is looking at current glucose, glucose momentum, carbs on board, insulin on board, and retrospective trends to predict an eventual glucose. Its current decisions are based on predicted, actual and eventual glucose.

If there is a dip in the predicted glucose below the Glucose Safety Limit, Loop will not recommend insulin even if the eventual glucose is above your Correction Range.

  • In Closed Loop mode, Loop automatically decreases insulin delivery using a temp basal of 0 U/hr until the predicted glucose exceeds the Glucose Safety Limit
  • When you tap on the Bolus icon in the Toolbar, Loop recommends insulin delivery only after predicted glucose is above Glucose Safety Limit
  • In Closed Loop mode, Loop automatically increases insulin delivery only after predicted glucose is above the bottom of the Correction Range

If the Loop predictions don't match your experience, your settings may need to be adjusted.

Testing

Open Loop mode shows you glucose trends without the influence of temp-basal or automatic-bolus from Loop. This is particularly helpful if you haven't used Medtronic sites/pumps or Omnipod prior to Loop. You may find that your basal rates and carb ratios can change significantly coming from other brands of pumps or from multiple daily injections (MDI).

Take the time to establish a good basal profile using the pump you plan to use for Loop while in Open Loop mode.

Test your insulin sensitivity factor (ISF) during Open Loop after your basal rates are established. Loop uses your ISF every 5 minutes to update predictions, so it's worth testing before turning on automated insulin dosing with Closed Loop mode.

Meal Entry

Loop recommends increased insulin dosing as soon as you save carbs.

Meal Entry is an important concept - there's a whole page devoted to it - but here's a quick summary. You tap on the plate icon in the Toolbar to start a meal entry.

  • Meal Entry:
    • In the Add Carb Entry screen, you must enter Amount Consumed, defaults are ok for other rows
    • The meal entry is not saved when you tap continue - Loop takes you to the Meal Bolus screen
    • In the Meal Bolus screen, you can save the carbs and accept or override the recommended bolus
    • Review the recommended bolus for the carb entry
      • Does the recommendation make sense based on your prior experience
      • Pay attention to the glucose prediction chart embedded in the Meal Bolus tool
      • Practice modifying when the carbs are expected and how long they are expected to last
      • Practice modifying the bolus recommendation - note how the prediction changes
      • When you are confident, you can save the carbs and deliver the bolus

Carb Absorption

Loop uses carb absorption as a component to every meal entry. Watch your meals and try to estimate how long they impact your glucose for various types of food. Notice when Loop would suspend basal or increase insulin delivery and ask yourself why it would be doing that. Ask if this is the same decision you would make. This effort will help smooth the transition to closed loop.

Manual (or Correction) Bolus

At any time, you can enter a bolus using the Bolus (double orange triangles) icon in the Toolbar. Loop offers a recommendation if the glucose prediction supports one. Review the Eventual Glucose section above to understand when Loop will recommend a bolus. The Loop recommendation can be modified by editing the Bolus amount.

More detail is provided at this link.

Troubleshooting

If you use a RileyLink, determine how far the link can be from your phone and pump, and plan where to carry the link. DASH Omnipod users do not need the RileyLink but should determine how far their phone can be from the pod without communication problems.

Learn to troubleshoot Red Loops and the cause of potential loop issues. You'll be less frustrated starting on closed loop if you know how to address these issues

Familiarize yourself with the "Bolus May Have Failed" notifications and how to handle them. Double-check the displays to verify that the bolus didn't enact before trying to give the bolus again.

Caregiver training

Caregivers for Loopers should learn how to use Loop. Consider giving caregivers an individualized quick info sheet on Loop. School staff or your child need to know how to handle a site change at school. Try to watch Nightscout while you get to know Loop so that you can become better at remote troubleshooting problems you might encounter.

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