Touchscreen meets insulin pump in Tandem’s new t:slim

by Adam Brown

“Design is a funny word. Some people think design means how it looks. But of course, if you dig deeper, it's really how it works … To design something really well, you have to get it. You have to really grok what it’s all about. It takes a passionate commitment to really thoroughly understand something, chew it up, not just quickly swallow it. Most people don’t take the time to do that.”

Those were the words of the late Steve Jobs in an interview with Wired in February 1996. More than a decade later, Tandem Diabetes Care took this idea to heart with its new t:slim touchscreen insulin pump, which it designed after conducting a remarkable 4,000 in-depth interviews with patients, healthcare providers, and caregivers. Tandem really wanted to get inside the minds of people who take insulin – pumpers and non-pumpers alike. The new pump was approved by the FDA in November 2011 (see new now next in diaTribe #38) and launched just last month. I was able to get trained on the t:slim at Tandem’s San Diego headquarters soon after it launched, and what follows is my experience wearing the device over the past week. So far, three themes have emerged: some clear differences from other pumps, a focus on simplicity and convenience, and an attention to safety.

Part One: Differences from Other Pumps

Adam’s Favorites

• iPhone-like touchscreen

• Rechargeable battery

• Highly customizable “personal profiles” for insulin delivery

From the minute I opened the shipping box, it was clear that the t:slim pump was somewhat different from other pumps I’ve used – included with the pump were a USB charging cable and adapters for both the wall and car. Even the included user manual comes on a credit-card-like thumb drive. But the most obvious difference between the t:slim and other pumps is the touchscreen. I found this to be the most compelling feature of the pump and a major departure from the button-driven devices I’ve used since I began pumping in 2002.

The Touchscreen

Most important, the touchscreen is easy to use, intuitive to navigate through, and responsive. I appreciated the screen’s very bright, high contrast, full color design, which also incorporates highly readable bold font and large icons that make selection easy and mis-taps rare. Unlike some other medical device touchscreens, I also appreciated that the t:slim screen did not require a lot of finger pressure to use – it’s right on par with using an iPhone or Android smartphone. The one minor shortcoming of the t:slim touchscreen is it doesn’t have the smartphone swiping (i.e., to navigate up, down, left, and right) that I’m so used to. Instead, you must hit a down or up arrow key, though this was a fairly minor inconvenience because few of the menus take up more than one screen length.

The Battery

Another departure from other pumps is the t:slim’s rechargeable battery, which lasts seven days on a full charge. A dead battery would take about 90 minutes to completely charge, and on average it takes about a minute of charge time for every percentage point of battery life (i.e., if the pump is at 80% battery life, that’s about 20 minutes to fully charge it). Tandem recommends plugging in the t:slim for 10-15 minutes every day to “top it off” – I did this while I showered (see water resistant information below) or when sitting next to my computer, and the t:slim would always return to 100% battery life. The pump can be charged whether or not you are connected to it.

Although a rechargeable battery is new to insulin pumps, I found it refreshing and fairly easy to remember to plug it in – I’m used to doing it for my Dexcom Seven Plus CGM, my LifeScan OneTouch Verio IQ blood glucose meter, my cell phone, my laptop, my iPod, and pretty much everything else these days. The included charger cable is the very common micro-USB computer cable used for many consumer electronics, and I was happy to see Tandem include a wall adapter and car adapter. There are also a variety of battery packs, solar chargers, and the like for those who will not have access to electricity (Tandem is not currently selling these but they are easy to find online). I was glad to hear this is an option since I know many pumpers that are into outdoor camping and backpacking where charging would be a challenge.

Personal Profiles

The third biggest difference between the t:slim and other pumps is setting up the pump’s insulin profiles and bolus calculator settings. Traditionally, a pumper sets up basal rates by time of day in one menu, an insulin to carb ratio by time of day in another menu, a correction factor by time of day in a third menu, and a target blood glucose or range by time of day in a fourth menu. The separate menus do not interact, meaning that a change in one parameter (e.g., the time a basal rate changes) is not reflected in the other menus. On past pumps, at least for me, this process has sometimes resulted in a disjointed insulin profile, with parameters that do not match up. Tandem has improved and streamlined this process, which is good news in our view because we worry a lot about optimizing glycemic management. In a recent dQ&A survey, fewer than 60% of patients and 50% of educators thought that their insulin pumps were configured optimally – very disappointing from a patient perspective!

In the t:slim’s personal profile menu, all four parameters – basal rate, correction factor, insulin to carb ratio, and target glucose – are set for a particular time of day. These appear in a single menu and are saved together. The entire day’s worth of settings is then saved within a particular profile, which you give a custom name and can easily and quickly duplicate. I have one profile called “Home” that is based on my level of activity at home and my normal diet and wake up time. But I also have a “Travel” profile with different settings, as well as a “Sleeping in” profile for going to bed later and waking up later. It’s very easy to toggle between these profiles, and it’s all located in one centralized menu. You can have up to six different personal profiles and up to 16 time segments within each.

A New Delivery Mechanism

Instead of a conventional piston driven delivery, where a mechanical screw drives a syringe built into a reservoir (the way a Medtronic, Animas, Roche, or Insulet pump works), the t:slim uses a micro-delivery technology. This means that very small amounts of insulin are shuttled from the reservoir to the infusion set, and the full insulin supply is never directly exposed to the user’s body (as it is with other pumps). Notably, the pump can deliver in increments of as little as 0.001 units, compared to 0.025 for the Animas OneTouch Ping and Medtronic Paradigm and 0.05 units per hour for the Insulet OmniPod. While I cannot say that I noticed a difference from these novel accuracy and safety features in my blood glucose numbers over the last week, I can say it was comforting to know that the pump has these innovations. Perhaps Tandem will eventually conduct studies to examine whether these are indeed beneficial for glycemic control, fewer pump-related accidents, etc.

Changing an Infusion Set and Cartridge

The one area where the t:slim was different from other pumps – but in a way that created more hassle – was when it came time to change a reservoir and pump set (the t:slim works with any luer lock infusion set). The process took me an average of around nine minutes with the t:slim, more than double the average of four minutes it took me on the Medtronic Paradigm and Animas OneTouch Ping. The process is slow for a few reasons: 1) the pump takes a bit of time to automatically clear air out of the new cartridge (I appreciated this, since air bubbles can cause some unexplained and frustrating highs); 2) because of the micro-delivery technology, it takes the pump a couple minutes to prime and fill the tubing with insulin; and 3) you are guided via step-by-step on-screen pictures and prompts, which take extra time to clear relative to the Animas and Medtronic pumps. As we understand it, the cartridge change process is a leading cause of calls into manufacturers’ support lines and one of the reasons Tandem included this extra guidance. In the future, I think Tandem could improve the process by prefilling the cartridges with insulin (similar to the Asante Pearl) or perhaps speeding the priming process by allowing users to turn off the pictures once they have the process down. On the plus side, the cartridge does hold 300 units of insulin, a notable feat considering the t:slim is about 25% slimmer than the Animas OneTouch Ping, the Medtronic Paradigm, and the Roche Accu-Chek Spirit insulin pumps. As a reminder, only the Medtronic Paradigm 723 and Roche Accu-Chek Spirit hold 300 units.

Part Two: Focus on Simplicity and Convenience

Adam’s Favorites

• Very simple menu layout, intuitive user interface, and fast navigation

• Bolus menu design

• Quick bolus feature

The marketing tagline for the t:slim is “touch simplicity,” which is most evident in the device’s user interface. The pump is very similar to the user interface concept and button design pioneered by the iPhone: 1) a touchscreen to use it; 2) a button on top that blacks out the screen and locks it; and 3) a button on the face of the device that immediately takes you back to the home screen at any time. Since the home screen is really the hub of the pump’s software and the starting point to perform any action on the device, I really liked having a single button take me there immediately. It was much faster than on other pumps I’ve used, where you keep hitting a back button to exit a menu.

The Menu Design

I did not need to open the instruction manual to figure out the t:slim’s menu layout, and the overall design made navigating through the pump quite fast. Taking a combination meal and correction bolus for 30 grams of carbs and a blood glucose of 165 mg/dl took me an average of nine seconds on the t:slim, compared to double the time (18 seconds) with the Medtronic Paradigm and nearly triple the time (26 seconds) with the Animas OneTouch Ping. I know a matter of seconds may not sound like a lot, but when you’re bolusing multiple times a day (I take an average of six boluses per day), every day, that adds up.

The t:slim’s home screen displays the most critical pump information: two large buttons called “Bolus” and “Options,” a battery life indicator (in both percent and an icon), an insulin reservoir indicator (in both units and an icon), the time and the date, and insulin on board (IOB) in both units and time remaining. IOB is my favorite part of the home screen because I use it so religiously, and it’s such a meaningful improvement for me over other pumps that only display IOB in units remaining and hide this vital information in a status menu.

The Bolus Calculator

Since bolusing is the most common interaction a user has with a pump, I appreciated that this was front and center on the home screen. Clicking the “Bolus” button immediately takes you into the bolus menu, where you can enter carbs and/or a blood glucose level if the carb calculator is turned on, or just insulin units and a blood glucose if the carb calculator is turned off. You can quickly override the calculator’s dose by clicking a box at the top of the screen and inputting your own number of units. “Options” allows you to suspend insulin, set up profiles, load a new reservoir (what Tandem calls a “cartridge”), set a temp basal, and view history.

The bolus screen is a perfect example of how the t:slim’s user interface is simple and convenient. The side-by-side, large block design makes it very clear what can be entered, while a running tally at the top totals the insulin dose. A tab at the bottom allows you to click and view the full delivery calculation in a nice vertical arithmetic layout. Entering a blood glucose value or number of carbs pulls up a touchscreen numeric keypad (like dialing a phone number), and cleverly, Tandem has included an addition sign that will tally the carbs from multiple foods. This struck me as a great addition considering how tiring diabetes math can sometimes be.

Extending and Quick Bolusing

After entering the information for a bolus, the final screen before delivery gives you the option of extending the bolus – this was just a toggle switch and was available for every bolus, unlike on other pumps where you must preselect an extended bolus before entering anything into the bolus calculator. The t:slim also has a great quick bolus feature that uses only the screen lock button on top of the pump. Increments can be in units of insulin or carbs, making the t:slim the only pump that offers either option for a quick bolus. I used this feature to program and deliver a bolus without looking at the pump (!) and to very quickly take a bolus without unlocking the pump screen and using the carb calculator.

Part Three: Safety

Adam’s Favorites

• 10 seconds to cancel a bolus

• A plethora of confirmation screens, alerts, and warning messages

It’s great to make a cool looking, sleekly designed insulin pump, but it’s also a medical device infusing insulin. Consequently, I was glad to see a vast array of safety features built into the t:slim – confirmation screens galore, alerts when you have not completed an action for 90 seconds (e.g., you were in the middle of calculating a bolus and forgot to deliver it), red bold text to draw attention to important items, an automatic screen lock following a bolus or when the screen is tapped three times in quick succession (e.g., to prevent accidental touchscreen taps while in your pocket), and a user interface feature called “dynamic error handling” that prevents the user from selecting illogical items in real-time (e.g., you can enter 100 grams of carbs, but the pump prevents you from adding another zero for 1,000).

My favorite safety feature of the pump was the cancel/stop bolus button. After programming and confirming a bolus, the t:slim gives you approximately 10 seconds to cancel the bolus before it ever starts delivering it. On other pumps, programming and confirming a bolus initiates delivery immediately, so unless you have lightning fast fingers, cancelling the full amount of the bolus is very challenging. I found this feature of the t:slim valuable when I had second thoughts about the bolus I just gave. The cancel bolus button also appears right on the home screen as a red “X” during the 10-second grace period, so there is no need to dig into a menu and hunt around for this feature.

Part Four: The t:slim’s Durability and Cost

Durability

As an outdoorsy and active person, I was initially concerned about the t:slim’s durability. Tandem has told me that if a user accidentally cracks the screen, the pump will be replaced under warranty. While I can’t say I did my own extensive crash tests, I know that many young attendees at the recent Children with Diabetes Friends for Life conference had “contests” to try and break the trial t:slim pumps, and it was pretty challenging for them to do so – I think in the end it took one t:slim pump thrown at another one to crack it (and it was still fully functional)! The starter kit comes with a hard plastic case that wraps around the pump for additional protection, and the t:slim touchscreen also has a pre-applied protective film. I have not worn the pump long enough to have too many accidental drops, but the durability will be on the top of my mind as I get more experience with the device.

Water Resistance

Unlike the Animas pumps and Insulet’s OmniPod, the t:slim is not completely waterproof. According to the company, the t:slim has been tested in three feet of water for 30 minutes (what’s known as an IPX7 rating, similar to Medtronic pumps) – essentially, it’s “water resistant.” However, I must confess that I’ve broken multiple pumps due to water damage, so this is a concern for me. The pump worked fine after I submerged it in a cup of water for ten minutes, though I will need to wear it for a longer period to fully test its durability and water resilience.

Cost and Insurance

And of course, the very, very important question is cost. Insurance companies typically pay for a new insulin pump once every four years, though this can vary. Tandem has already signed contracts with some major insurers, and is currently working with customers on a case-by-case basis to obtain insurance coverage. We understand that the t:slim has a higher list price (about $6,995) than the Medtronic Paradigm Revel (about $6,500), Animas OneTouch Ping (about $6,300), and Insulet OmniPod (only around $600 for the starter kit, although “pods” are more expensive than sets on an ongoing basis), so that is an important consideration for those who must pay co-insurance. However, Tandem has a large staff dedicated to reimbursement, so if you are interested in getting the t:slim pump, the best way to figure out your situation is to contact Tandem directly.

Closing Thoughts

I was impressed and plan to keep the t:slim assuming my insurance will help cover some of the cost (fingers crossed!), though the devil will be in the details since I changed to my current pump fairly recently. That said, I’m definitely still interested in trying the upcoming Animas Vibe (integrated with the Dexcom Gen 4 CGM), Insulet’s smaller second-generation pod, and Medtronic’s MiniMed 530G with low glucose suspend – as a reminder, all these devices are currently under FDA review or will be submitted to the FDA soon. Indeed, this is a great time for patients with so many innovations coming, and I had a great week trying out something so new. For more information on Tandem’s t:slim, see new now next in diaTribe #38 and Tandem’s website at http://www.tandemdiabetes.com/products/t-slim/.