Last night I was up until 2 am feeding my daughter low foods and waiting for her blood sugar to go up. It’s something I haven’t done in six weeks and haven’t really missed. Today, of course, I walked around yawning all day wondering how I was going to get through the day. I realized that up until a short while ago, nights like this were the rule, not the exception. Yet, I was amazed at how quickly one forgets how exhausting it is to manage T1D the “usual way.”
Let me explain.
In October my daughter, Tia, or “the professional lab rat” as we often refer to her, enrolled in a pivotal trial for the Medtronic 670G Hybrid Closed Loop System. In November, she started using the system in Hybrid Closed Loop (HCL) mode, or “Auto Mode” as it is called on the pump. It has been truly a life-changing experience for us to use this technology that is expected to be on the market in April 2017. We can’t wait until everyone can get their hands on this!
While the pump is in Auto Mode, the pump modulates the basal rates throughout the day and night delivering micro-doses of insulin when the sensor glucose readings are above the target BG. The target blood sugar is preset to 120 throughout the day and night. The algorithm takes into account your current sensor glucose, your active insulin, your sensor glucose rate of change, and based on all of those variables will either deliver a micro-bolus of insulin or will not deliver insulin every five minutes all day long. It also learns your patterns, so it adjusts based on what has happened in previous days.
A Hybrid Closed-Loop system means you still have to bolus for meals as you would with all current pumps: you need to count carbs and enter them into the pump and the pump calculates your dose based on your insulin to carb ratio and then you need to press a button to deliver the bolus.
Since the system is a “basal rate modifier” it cannot deliver enough insulin by modifying the basal rate to compensate for a missed meal bolus. However, if your insulin to carb ratio isn’t precise, the pump can make up for it through the auto mode. But forget to bolus, and you will go high.
The system also has some safety features in place. For example, if you run above 250 for three hours, the pump will alert you to check your BG and take action, i.e. bolus for the high BG. The pump only delivers micro-boluses of insulin at this point. It won’t deliver a full unit of insulin or more on its own. Similarly, if you are above 300 for an hour it will request a BG check. If you have been low and it hasn’t delivered any insulin for two and a half hours, it will also request a BG check and suggest that your treat your low to make sure you are safe. If you don’t take action to check your BG when the pump alerts you to do so in these situations, you will be “bumped out” of Auto Mode into “Safe Mode” where the pump delivers a pre-calculated basal rate based on your past insulin needs for another one and a half hours. If you still don’t take action, it will revert back to your pre-programmed basal rates.
I admit that when I first heard about all these safety features, I threw my hands up in the air in despair thinking–this system wasn’t designed for *real* diabetics. Tia’s going to be bumped out of Auto Mode all the time. Come on! She’s a teenager! She has better things to do than to pay attention to her blood sugars! She also ignores her pump alerts, so I didn’t think all the alerts coming from this new pump would make any difference.
What I didn’t realize was that when she is in Auto Mode, she would not be spending as much time over 250. She’s actually gone from being in range 60% of the time to being in range 80% of the time. (“In range” is 80 – 180). And the most amazing thing is that this has happened with less work on our part. There are actually fewer alerts and alarms, less lows, and low foods consumed when she does go low.
Overall, it’s been quite an amazing experience!
Earlier this week her pump started draining batteries at a furious rate, so we had to get it replaced. When starting on a new pump we have to give it 48 hours in open loop mode so that the pump has time to learn her patterns before going into Hybrid Closed Loop and Auto Mode. That’s why last night, when she was not yet back in Auto Mode, I was up feeding her low foods at midnight and waiting for her BG to come up. Tonight I’m up because at midnight I can switch her pump back into Auto Mode. I can’t wait until I’m able to let the pump take over again. That’s when I get to go to sleep and know that she’s back in good hands.
Disclaimer: I am in no way affiliated with Medtronic Diabetes, and I do not receive any financial compensation or products from them in return for my opinions. I was not asked to write this blog by anyone at Medtornic, the people running the study, or anyone involved with the study. My daughter participates in many trials using many different devices. This is the first time she is in a pivotal trial where she has had the opportunity to use a closed-loop system at home for an extended period of time.