So a week ago Friday I decided to start with LOOP. I just followed the directions at https://loopkit.github.io/loopdocs/setup/build/installing/ It was a bit intimidating at times because all the involved systems are so big and unfamiliar, but I just followed the instructions step-by-step and the result was working software on my iPhone. The hardest part actually was signing up for the Apple developer account: somehow an essential button wasn’t appearing on the web page for me, so I was stuck until the button finally showed up after a few reloads of the page. And then the several-hour wait for the approval email from Apple.
I started the software open loop running to my old 723, which had firmware 2.4A. Unfortunately, I had forgotten that my old 723 was replaced under warranty because of some kind of hardware error, and the one I actually have is firmware 2.5A. It works fine in open loop, but the pump won’t accept any commands related to dosing insulin. (They took those commands out to protect us from the hackers who might surreptitiously give us fatal overdoses by radio.) When I first put the battery into the 723 it rebooted itself twice in the first 5 minutes because of internal errors, but after that it settled down and seems to be working properly.
In open loop I enjoyed seeing the loop’s prediction curve showing what it expected my CGM graph to look like in the future, and seeing the curve change over time as reality failed to match the expectations (typically because of my underdosing for meals.) The prediction graphs did cause me to be less aggressive in corrections because of the predictions that my rising trend would get better all by itself starting in 20 or 30 minutes if I just wait. I worked through multi-hour moderate highs when the suggested corrections were not enough, but I’m spending much less time low — my worst problem. It worked better when I found the bolus tool (the double down triangles in the middle at the bottom of the screen. To me, this is the “I want more insulin” button. It suggests a correction bolus that really does help, and acts as a conservative sugar surfing wizard while keeping me away from rage boluses.
I was able to get an ancient 515 demonstrator model from my endo’s office. It got an A21 error right away, then rebooted. A21 might mean a failure of the internal battery that keeps the pump running while you switch the AAA cell. After rebooting it seemed ok, so I entered my settings, put in a filled reservoir and tried to prime. The plunger moved to the reservoir at high speed, and then kept right on on going, spraying a hundred units of insulin out of the tube before giving an A33 error. That error might mean failure of the sensor that detects back pressure on the plunger: the pump never knew that it had contacted a filled cartridge. But the pump didn’t brick itself. After rebooting and many many rewind/prime attempts, I finally got the screen saying 0.0 primed which means it did sense a filled reservoir. By then there were only 60u left in the reservoir, but I decided to run closed loop with it.
LOOP is outstanding. Far away from meals it keeps me more or less in a flatline with no attention from me at all. And I’ve been making my carb ratio and correction sensitivity more aggressive, which is helping LOOP get a good response after eating.
It’s clear that LOOP was designed for the convenience and comfort of the pump user, not the pump manufacturer’s legal staff. It is wonderful to be able to get a meal bolus with a minimal number of keystrokes; the (user-adjustable) safety guardrails in the software are quite thoughtfully designed to protect against blunders without being intrusive.
After the initial 60u ran out I went through the same ordeal with the next reservoir. Multiple A33 errors and reboots. By the time the pump would let me stop priming there was only 12u left. This is not sustainable.
After the 12u ran out, I decided to prime against the eraser-end of a pencil rather than against a reservoir filled with insulin. It took a half hour, but I managed to get out of priming mode with the plunger at about the 160u mark. So I filled a reservoir to 160, screwed it into the pump which pressed out just a few drops of insulin, and have continued looping. Quite a nuisance, but LOOP is so wonderful that it’s worth it, and I’ll keep doing it this way until I break the pump because it doesn’t know to stop the motor when there’s too much backpressure. (This also probably means it can’t detect occlusions, but I’ve only had one in the last 5 years.)
Any tips on finding another pump? I found nothing suitable the past couple days on craigslist or ebay. MedWow shows some expensive pumps that might work if they are not scams, but the LOOP documentation at https://loopkit.github.io/loopdocs/setup/requirements/pump/ says “Medwow has been fairly frustrating for most people; poor response rate, high prices” and then goes on to describe all the ways we can get scammed when web-ordering a used pump from a random posting. So that makes me extra wary.