The longest yard
OK. Technically, it isn’t a yard. It’s 43 inches. So it’s a yard-and-a-fifth. That sounds more like something you’d order at an Irish drive-thru package liquor store than something that deals with diabetes, doesn’t it?
But what I’m talking about this morning is the length of my infusion pump tubing. I prefer sets with long tubes and short 90-degree cannulas. When it comes to cannula length, if you’re lean like me, or athletic and muscular (not like me), then you should use a short cannula—or an angled set. It you are normal, fluffy, or King Size, then you should use the longer cannulas. But when it comes to tubing length, the choice has more to do with lifestyle and wardrobe than anything else.
On the plus side, long tubes let you be more creative about where you place your set and where you carry your pump. But on the negative side, all that extra tubing seems to have a magnetic attraction to passing door knobs and the like. To be blunt and crude, frankly, I like the longer tubing simply so I can leave the pump on my belt or in my pocket when I go to the bathroom. I’m tall enough that I need the long tubing to reach from my stomach to my ankles.
But t:slim might cause long tube lovers to re-think their desires. Oh dear… that sounded rather pornographic, didn’t it? Allow me to restate: the t:slim might cause fans of the 43-inch long infusion set tubing to re-evaluate their choice.
Because it’s the longest yard. The t:slim, despite its racy look, is no thoroughbred when it comes to site changes. Here, I’ll take you through the process, and it starts with a luggage tag.
What’s in the cartridge, you ask?
I’m glad you asked, because the very first thing Rio and I did after the first site change was some Spanish Inquisition-style mad science on the discarded cartridge. I had read that inside the cartridge was a bag-like reservoir for the insulin, and we wanted to see it. The bag is a real reservoir, not a semantic mind game like other pump makers play. The t:slim bag holds a supply of insulin, 300 units worth, and then the machine uses a tiny micro-pump to out pull a unit or so at a time as needed. This is touted as being a great safety feature for two reasons; it’s supposed to assure bubble-free delivery; and it’s a literal, physical barrier between you and a fatal overdose of insulin.
I don’t know if it’s ever happened, but in theory, a traditional pump could freak out and deliver its entire contents to you all at once. I never lost any sleep over this fact when I wore other pumps, and I’m not sleeping any better now that I’m wearing a “safer” pump. After all, in theory, the t:slim could freak out, too, and deliver its entire contents. I’d be just as dead—it would just take a bit longer.
Anyway, getting the cartridge apart to see the bag inside turned out to be quite a bit more difficult than I expected. We were able to snap the part off, but getting into the main body took a hammer, two knives, a lot of swearing, and finally two pairs of pliers.
Yeah, we had to crack it open like a walnut.
For some reason, I expected the bag to be black, but it’s clear, and looks disconcertingly like a used condom.
Here’s where t:slim, once again, diverges from the pack. You attach an empty to the pump. It then sucks all the air out of the bag, at which point you fill it up in situ, as they say in archeology. Which leads me to another “surprise” the t:slim had in store for me.
Most pump companies have their own proprietary systems for filling the reservoir, the best designed probably being Med-T’s elegant docking collar that holds the insulin vial on one end and the “reservoir” on the other end. But when I opened up my first pretty black and white box of Tandem reservoirs I found a bunch of garden-variety BD 26 gauge, 3/8 inch needles, and a pile of 3 ml syringes. All of them individually and separately packaged, of course.
Well, I guess there’s no point in re-inventing the wheel, especially when the wheel needs to be FDA approved, but somehow this came as a surprise to me. It struck me as somehow counterfeit, like a sleek sports car that turns out to be a fiberglass kit on a VW chassis. It’s also more packaging to throw away, and more crap to carry around in my Go-Bag.
Anyway, to fill the empty cartridge that’s waiting for you on the pump, you must first unwrap the syringe. Then unwrap the needle. Attach the needle to the syringe. Draw the plunger down to fill it with air. Inject the air into a vial of insulin. Then draw the desired amount of insulin into the syringe. The max is a whopping 300 units, almost a third of a vial.
I gotta tell you, when you draw down 300 units of insulin in a fat two inch-long syringe, it’s an intimidating amount of fluid.
At this point it’s worth mentioning another nice feature of the t:slim. If the screen times out on you, when you wake up the pump up again, it remembers where you were: It doesn’t return you to the home screen.
If there’s a minimum fill volume, I couldn’t find it in the manual that doesn’t exist in the real world—the t:slim manual exists only as array of ones-and-zeros in the digital universe.
Now, at the top of the cartridge, next to the short length of tubing that extends out of it, is a small white dot. That’s the fill port. You just stick the needle into it, and inject the contents of the BD syringe into the port. That fills the baggie inside the cartridge.
Next, you attach your infusion set tubing to the t:slim’s cartridge hub. This part is a bit bizarre. Rather than attaching the tubing to a hub on the pump itself, like everyone else does, the t:slim’s luer lock connection is downstream about two inches. I can’t say for the life of me why this is. Maybe it had something to do with keeping the pump thin, but it makes the line oddly bulbous in a bizarre location, and makes the consumer-gadget-looking pump look like a medical device again. That said, carrying Mr. Pump in my pocket, the hub is hidden. But if I start using one of the belt cases, it will become more obvious.
All of that up to this point is pretty straightforward, but next comes the loooooooooooooooong part. The t:slim is painfully slow to fill the infusion set tubing. And I mean that literally. Why, this entire post was written while I waited for the pump to fill my tubing.
The t:slim primes at a rate of 7 units per minute. A 43-inch tube holds somewhere in the neighborhood of 30 units of insulin, so the prime time (pardon the pun) is six fucking minutes.
Of course, it feels like six fucking hours.
It’s by far the slowest --filling pump I’ve ever encountered. The reason it takes so long is because of the design we discussed earlier. The pump literally has to pump a unit of insulin or so at a time out of the reservoir bag and into the “micro-delivery” chamber, and from there send it on up the line.
It’s tedious. But it’s not like you have to do it every day, either. So how often do you have to do it? Humalog is approved for use in the pump for 48 hours and Novolog for 72; but you know what? You can carry a pen of either at room temp for a month. I have a hard time believing that you couldn’t leave either insulin in the cartridge for as long as it takes to use it up.
As I was getting the blues waiting for the first drops of insulin to come out the business end of my infusion set, I found myself wishing insulin were blue, not clear. My old eyes aren’t good enough to see the clear insulin marching slowly up the transparent tubing. If insulin had color, it would be easier to see it in our tubing. Easier to see bubbles, too.
Anyway, after your latte and manicure, and checking your stocks online, your tubing is finally full and you can attach the set to your bod. It’s a standard luer lock, so you can use anybody’s infusion sets. I started off with the Animas/Unomedical Inset—which has a crafty disposable inserter device that also stores the tubing, all in a portable plastic hockey puck. The set has a smooth, low-profile arrowhead-shaped hub with a fast and easy disconnect.
I haven’t field tested it yet, but I’m pretty sure that if you disconnected for an intimate encounter, you’d be highly unlikely to scratch your partner with it. I must put that on my “to do” list.
Once the set is in place, you need to fill the cannula, and the t:slim can be programed to remember how much your sets need. You also have the option to activate a site change reminder at 1, 2, or 3 days. Not four. Not seven. Why? Probably because we are supposed to change the site every two-to-three days.
But my thinking on this has been shifting recently. After all, we wear Dexcom CGM sensors for a full week (or more). What’s the difference between a CGM site and an infusion site? Both have sticky tape on our skin, probably made by the same company, as there are only a few makers of this kind of tape in the world. Both have something that pierces the skin—either a sensor or a cannula.
At any rate, if you are insulin-sensitive enough that 300 units will last you more than three days, and if your skin is tough enough to hack longer wear, the site change reminder is useless to you.
And that’s all there is to the site change. With a final blue splash, you’re pumping insulin again.
Next week: Profiling isn’t just for the FBI