As follow-up to last month’s narrative of a cardiac abnormality thankfully detected by wearable devices, this engineer details the monitoring system he subsequently donned for a month.
Two-plus years ago, my contributor-colleague John Dunn described his most recent experience with a wearable cardiac monitor. And, as any of you who read one of my last-month blog posts already know, I more recently followed in his footsteps. I don’t yet know the outcome of my heart health study; my follow-up appointment with the cardiologist is a week away as I type these words. Regardless, I thought you might still find it interesting to learn about the gear I toted around, stuck to my chest (and in my pocket) for 30 days, and my experiences using it.
The system I used was Philips’ MCOT (Mobile Cardiac Telemetry), specifically its “patch” variant:
Here’s an overview video; others, plus documentation, are at the product support page:
I took several “selfies” of the sensor in place on my chest but ultimately decided to save you all the abject horror of seeing any of them. Instead, I’ll stick with these stock images:
My initial scheduled meeting with the cardiologist took place on December 12, 3+ weeks after our “introduction” at the emergency room. I’d been on both beta blockers (to regulate my heartbeat) and blood thinners (in case my prior irregular rhythm had resulted in the formation of a clot) since my initial visit to the hospital in mid-November. The cardiologist ordered the monitor, which arrived a bit more than a week later; I began wearing it the day after Christmas.
Here’s the box that the system comes in:
The first thing I saw was the initial sensor patch, along with the return shipping packaging bag. Below it was the template I used for proper placement each time I stuck a patch on my chest:
The bulk of the contents were contained in two inner boxes, the first labeled “Getting Started” and the second referred to as “Monitoring”. Inside the first:
were several primary items:
along with installation and operation overview instructions:
The monitoring device, both here and in subsequent photos accompanied by a 0.75″ (19.1 mm) diameter U.S. penny for size comparison purposes:
whose dimensions and Android operating system foundation, along with the legacy presence of an analog headphone jack alongside the USB-C port:
and a multi-camera rear array in a specific arrangement:
suggest it to be a custom-software derivative of Samsung’s Galaxy A52 smartphone, introduced in March 2021:
It came with the translucent green case pre-installed, by the way. Here are some other overview images of the smartphone…err…monitoring device (its left side was unmemorable so I didn’t bother):
Next up was a small scrub pad used to further prepare my chest for patch application, after initial hair shaving. And, of course, there was the sensor itself:
Its edge arrived already abraded; I’m guessing that it had already been popped open, with its rechargeable battery subsequently replaced, at least once prior to its arrival at my residence:
Now for box #2:
More instructions, of course:
along with more patches, a more detailed instruction booklet, and the dual-charging unit:
The AC/DC adapter has two USB-A outputs:
which can be used in parallel:
One, connected to a red USB-A to USB-C cable, is used for daily recharge of the “monitoring device” (smartphone). The other (black, this time) cable terminates in a charging dock for the sensor, which I used every five days in conjunction with (and in-between) the patch removal and replacement steps:
Here’s how the initial “monitoring device” bootup went (since this was a custom Android-plus-app build, I wasn’t able to grab screenshots directly from the smartphone, perhaps obviously):
After initial charging of both the monitoring device and sensor, I continued the setup process:
Here’s what a patch looks like when you first take it out of the package; top:
and bottom:
Pressing down on the sensor while aligned with the patch base snaps it into place:
A briefly illuminated LED subsequently indicates that the sensor is correctly installed, at which point the monitoring device is able to “see” it (broadcasting over Bluetooth, presumably Low Energy):
At this point, you can peel away the protective clear plastic cover over the back side adhesive:
All that’s left is to press it into place on your chest…and then peel off the existing patch, pop out and recharge the sensor and redo the installation process five days later:
Lather, rinse, and repeat until the total 30-day cycle is over, which the system thoughtfully tracks on your behalf. Then ship it all back to the manufacturer.
The monitoring device, which regularly receives data transmissions from the sensor, periodically then uploads the data to the “cloud” server over an LTE or EV-DO cellular data connection.
If you forget to keep the monitoring device close by, data won’t be lost, at least for a while. There’s an unknown amount of memory onboard the sensor (yes, I searched for a teardown, alas unsuccessfully), albeit presumably not the full 2 GBytes allocated to this alternative device designed solely for local data logging. But the monitoring device will still alert you (both visually and audibly) to the lost wireless (again, presumably Bluetooth’s LE variant) connection:
You’ll also be alerted if the sensor’s integrated battery drops to a low level and recharge is necessary (I proactively did this every five days, as previously noted, since I’d received six total patches):
If you feel like something’s amiss with your “ticker” (heart pounding, fatigue, etc.) you can tap on the icon at the center of the display and the monitoring device will send an alert “flag” for subsequent correlation with the potential cardiac arrythmia data collected at that same time:
And in closing, here are some shots of other monitoring device display screens that I captured:
By the time you see this, assuming I don’t need to reschedule for some reason, I will have met with my cardiologist and gotten the (hopefully positive) results. I’ll follow up in the comments. And please also share your thoughts there! Thanks as always for reading.
—Brian Dipert is the Principal at Sierra Media and a former technical editor at EDN Magazine, where he still regularly contributes as a freelancer.
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