Continuous Glucose Monitoring
It goes without saying an accurate non-invasive (optical) glucose measurement would have a stunning impact on improving diabetic’s lives and reducing the World’s healthcare costs - Allan Stephan
image by: Dexcom
My hiking shoes were just laced up when there was a frantic vibrating in my pocket. I reached inside, took out the iPod-sized medical device and checked the screen. Up at the top, where my blood glucose would normally read, was a series of glowing question marks. Great.
It had been over a week since I’d inserted my last continuous glucose monitoring (CGM) sensor and it had started acting up earlier that morning, with missed readings. Each of these disposable sensors lasts for about a week, transmitting the number representing my blood sugar level in real time to a small handheld receiver. It figured that just as I was about to head out on a Saturday morning hike with my husband and two daughters, it would choose that moment to finally die. It always happens like that.
I found my husband in the kitchen, packing some water and snacks. “My CGM just died,” I said. “I’m going to stay here and wait for the new sensor to start up.”
“That’s lame. Can’t you just take a bunch of extra test strips?” he asked, referring to the tiny plastic strips my fingerstick blood glucose meter uses. But unlike my CGM, this device only gives me a reading each time I lance a drop of blood from a finger. I could feel my heart rate rising at the prospect of hiking without the constant blood sugar feedback I’d come to depend on since I first started using CGM technology six years ago.
In the last 28 years of living with type I diabetes, I’ve lived through a progression of treatment technologies. When I was diagnosed at the age of 11 in 1986, my parents were handed a couple bottles of insulin, a box of syringes, a vial of glucose testing strips, and a prescribed diet of an exact number of bread, protein, fat, and fruit exchanges to be eaten at each meal and snack. For the rest of my life.
Back then, I’d lance my finger and place a huge drop of blood on a long strip pulled from a tall white vial. Wait 60 seconds. Wipe the blood off. Wait another 60 seconds. Then I’d compare the color at the end of the strip with the range of blues on the bottle to get a general idea of what my blood sugar was, two minutes ago. The colors ranged from that of a robin’s egg (too low) to the blue of a summer’s sky (just right) to dark cobalt (far too high).
Electronic blood glucose meters became available a few years after my diagnosis, and I received my first one in 1990. They offered far more precise blood glucose readings in much less time than the old visual strips. While the size of these fingerstick meters has shrunk considerably (my first meter was the size of a large portable hard drive and the one I use now is shaped like a snack-size candy bar) their function hasn’t changed much in the past 25 years.
My current fingerstick meter sucks a miniscule drop of blood from the tip of a finger and spits my blood glucose number back at me in 5 seconds. I very rarely give myself a shot with a syringe these days. I have a constant stream of insulin infused in my hip via my insulin pump, which looks a lot like an old fashioned pager. I can pop in my current blood sugar number and the amount of carbohydrates I’m eating and the pump will calculate the precise dose of insulin to give, to keep my numbers in the right range.
That’s the theory anyway. In reality there are tens if not hundreds of factors that make my blood sugar rise and fall on a moment by moment basis. The weather. Lack of sleep. Exercise. Lack of exercise. A cold coming on. Stress. My period. For all these reasons, I’m grateful for the latest diabetes technology: the continuous glucose monitoring system.
Via a teensy wire inserted in my side with a plastic transmitter stuck on top, I get a blood sugar reading every five minutes on a handheld receiver that looks like an mp3 player. I can view a graph for the previous three, six, or 24 hours that shows how my number is trending: steady, up, down. Arrows too, if it’s rising or falling at an unnerving clip. It even emits a piercing alarm if my number rises above my set threshold, or below it.
I still use my handheld glucose meter, as CGM readings can lag slightly behind blood values and the device needs to be calibrated twice a day with a fingerstick reading. But I’ve come to depend on the little device that lives in my pocket in my attempts to keep my blood sugar in the right range and avoid both high and low blood sugar—the results of which can be the destruction of blood vessels, nerves and tissues, and death, respectively.
Those risks are why I’d shuddered at the thought this particular morning. The last time I went hiking without my CGM I had narrowly avoided disaster.
My sensor had recently gone out but I was determined to go for a late afternoon walk with my husband and our toddling daughter. My blood sugar was a bit high so I figured the exercise would do me good. I took a tiny amount of insulin to help bring the level down.
Our home lies on the edge of a drippy Washington state rainforest. We’d hiked up through the trees and had nearly reached the top of our favorite hill with a sweeping lookout over the wooded valley. Suddenly, my legs felt like I was walking through caramel, that slugging, dragging feeling you’ve likely had in a dream. The energy had simply drained from me. I fumbled in my pockets for my blood glucose meter, the first thing I do whenever I’m feeling off. It took me longer than normal to go through the motions: open the vial of strips, insert one in the device, use my lancer to draw a drop of blood out, place the strip against my finger to sweep the blood in.
5…4…3…2…1. The reading flashed on screen: 35 mg/dl.
“I’m a little low,” I said to my husband. “I need to sit down.” I sat on a nearby rock and started shoving Smarties into my mouth. The truth is that 35 is more than a little low. It’s nearly blackout time. I had no idea my blood sugar was dropping so fast without the CGM alerting me to it. My heart was pounding. Sweat beaded up on my forehead and started trickling into my eyes. My entire body shook and shivered.
I must have eaten 10 rolls of Smarties in two minutes. My hands and face and clothes were covered in pastel dextrose dust. I begged for water, worrying now that I’d choke on them, my throat dry as bone.
Slowly but steadily a calm began to seep up from within. The shaking subsided and the fog cleared from my brain. I checked my glucose again: 85. I’d be okay. This time. So this morning, I told my husband to go ahead and take the girls hiking himself. You’ll have a great time without me, I told him. Won’t have to wait for me to check my sugar every five minutes.
After they left, I got my CGM supplies out and readied to put a new sensor on. I ripped open an alcohol swab and cleaned a circle of skin on my side. Love handles come in handy here. I opened the package containing the new sensor and insertion device that looks like an enormous syringe. When my skin was dry, I peeled the tape from the end of the new sensor and stuck the entire contraption to my side. I always hold my breath for the next step: slowly pushing the plunger in, I can feel the needle piercing my skin, a full inch in. Usually, this hurts like hell.
I slowly back the plunger out and the needle withdraws. I can’t see any of this as there’s a plastic casing around everything. The inserter unclips, then I pop the little plastic transmitter onto it. Done. I grab the handheld receiver and select the “Start Sensor” function. A small green countdown circle appears in the upper right corner. The new sensor warm-up has begun. I won’t get any readings for the next two hours while the sensor does some FDA-approved thing. So I wait.
This part is far worse than the quick pain of insertion. Now, I feel naked without being able to take a quick glance at the CGM receiver to see where my glucose level is. I grab my meter out of my purse and take another reading. Still the same as when I woke up. That’s good.
I haven’t eaten breakfast yet and am starving. But if I eat some carbohydrate-laden food, I’d have to take some insulin to counteract it, keep my blood sugar from going up. But with that, there’s always the risk that I’ll take a little too much, landing me with a low blood glucose in an hour or two. I know this anxiety is ridiculous: There are diabetic people everywhere who take insulin for meals without a CGM in their pocket. I did the same for well over 20 years. And yet without my trusted device there to tell me what my blood sugar is up to, at this exact moment, I’m hesitant to make any move that could result in error. I fry up two eggs and eat them slowly. They’ll tide me over.
I look around our home. Disaster. I might as well spend my two hours cleaning, so I get the vacuum. While I’m working, there’s a twang of something in my body. A zap of tiredness. It passes in microseconds but leaves behind the what if? Sometimes that’s the only warning I have that my blood sugar is about to drop. Panic. My heart races as I rush back to the kitchen where I left my meter laying on the counter. My hands are trembling as I grab a strip from the tube, jab, and countdown.
It’s the same number as before. All good. But I’m in full-on adrenaline mode now and have to sit down and wait for it to pass. Maybe I should grab a magazine to read instead and vacuum later. I check my CGM receiver again and see that the warm-up symbol has advanced. Just over an hour to go.
As I’m sitting there, trying to figure out what to do with the next hour, irritation grows. I feel paralyzed. Sick of depending on these stupid devices. I feel like crying. This happens at least once per day.
Sometimes, I try to remember what it was like when I was a kid with diabetes. For years I had nothing but insulin, syringes, and my bulky glucose meter that I probably only used once or twice a day. Now I’ve got a $6000 pump hooked up to me infusing human-like insulin, a sexy handheld meter, and my CGM spitting out glucose readings constantly on another screen. I try to imagine living without any one of them, and I simply can’t. I hardly remember what it’s like to take multiple daily shots of insulin and the thought of testing my blood sugar only a handful of times per day makes me wince.
All of these devices can and do fail. My insulin pump has broken numerous times over the years and had to be replaced. Pump tubing kinks, insulin goes bad in the heat. Hands covered with unseen food residue causes errant fingerstick meter readings. My CGM sensor simply falls off my body sometimes or the receiver breaks when it falls to the floor. Diabetes technology has given me the confidence to travel, have a family, live an active, mostly normal life. But knowing that any one of the things I depend on to live can be taken away at any moment can make me feel more vulnerable than if this technology didn’t exist at all.
Even with all the benefits of diabetes technology advancement, I’ve still considered ditching all of these devices. They are expensive, and they don’t always work. I’ve come to depend on them to live a full life, and that makes me feel defenseless against their flaws. There are some in the diabetes community who advocate going back to basics: limiting carbohydrates, multiple daily injections of insulin, fingerstick blood sugar checks only, to avoid the known anxieties that come with the constant feedback of CGM.
Then there’s the other camp, those working tirelessly to bring about technology to improve the lives of those living with diabetes, such as the artificial and bionic pancreas projects and CGM in the Cloud. My weekly two hours without CGM reminds me not of what my life was like before it, because then I couldn’t imagine the wonderfully secure feeling of the device quietly monitoring the unseen. It reminds me that my future with diabetes technology will be even better, despite the sometimes paralyzing fear of its failing to do the work my pancreas can’t.
Back to the kitchen again. This time I grab a square of dark chocolate from the cupboard. It is delicious. A handful of almonds wouldn’t hurt either. I try to distract myself for the next 45 minutes. Logically I know that my blood sugar will be fine during that time. I could check it with my meter at any moment for goodness’ sake.
Sometimes I think I have a sort of blood sugar PTSD during these warm-up times as flashbacks of near diabetes disasters arrive from my memory, unwelcome. The hot afternoon I spent carrying groceries in from the car, my baby daughter left on the floor of the kitchen in her car seat. I feel woozy, check, and am 28 mg/dl. I shovel in handfuls of marshmallows as the edges of my vision start to grow dark. Or the time on an overnight trip on our sailboat when I couldn’t stop vomiting. Was it seasickness or the 450 mg/dl glucose meter reading, a result of kinked insulin pump tubing?
I try not to think of diabetic friends I’ve known that did not survive such disasters.
My CGM receiver buzzes again in my pocket. This time the calibration symbols are on the screen. I check my glucose with my meter, then punch in the number, twice. I wait, probably not aware I’m holding my breath again. The reading pops up at long last at the top of the screen and the new graph begins.
Right then, my family comes tumbling in through the front door. My oldest daughter a stream of steady commentary about all the things she saw in the woods, my youngest wailing that she’s hungry as she heads for the kitchen. I hug them all and tuck the CGM receiver back into my pocket, assured that it’s watching over me again.
Source: Sara Dawn Johnson, Modern Life Without a Pancreas, The Atlantic, September 23, 2014.