The Patient Who Became the Inventor: How Living With a Broken System Fixed It

When the Experts Don't Have the Answer

The thing about chronic illness that healthy people rarely understand is the paperwork. Not just the insurance forms and the referral chains, though those are their own particular punishment. The real paperwork is internal — the endless documentation a patient keeps in their own head, cataloging symptoms, tracking patterns, building a case that nobody in a white coat seems to want to hear.

Sarah Kreps kept that kind of paperwork for eleven years.

She was twenty-six when the symptoms started: fatigue that sleep didn't fix, episodes of dizziness that came without warning, a heart that seemed to forget its rhythm at inconvenient moments. She went to her primary care physician. She was referred to a cardiologist. She was told her tests were normal. She was told she was anxious. She was told, in the patient way that doctors deliver bad news that isn't technically bad news, that some people just feel this way and the best thing is to manage it.

She managed it. She also kept the paperwork.

The Diagnosis That Arrived Late and Changed Everything

It took a decade and seven physicians before someone finally said the words: postural orthostatic tachycardia syndrome, or POTS — a disorder of the autonomic nervous system that affects blood flow and heart rate, particularly when a person moves from lying down to standing. It is estimated to affect somewhere between one and three million Americans, the majority of them women, and it is famously underdiagnosed. The average patient waits five years for a diagnosis. Kreps waited eleven.

POTS is not, by most clinical definitions, life-threatening. It is, by the experience of nearly everyone who has it, life-altering. The symptom that Kreps found most debilitating was the unpredictability — the inability to know, on any given morning, whether her body would cooperate with the day she had planned. She had left a career in marketing. She had stopped making long-term commitments. She had learned, as chronic illness patients do, to hold her life loosely.

The diagnosis helped. Having a name for the thing gave her access to a community, a literature, a set of management strategies. What it didn't give her was a solution to the core problem: her body's inability to regulate itself during position changes, particularly in the hours after waking.

The existing medical devices for monitoring POTS symptoms were clinical-grade, expensive, and designed for hospital settings. The consumer wearables on the market in the mid-2010s tracked steps and sleep but couldn't capture the specific physiological data — heart rate variability in real time, positional changes, recovery time — that would have actually helped her manage her condition.

So she decided to build one.

The Bedroom Lab

Kreps had no engineering background. She had a marketing degree, a library card, and a laptop. She also had something that no biomedical engineer working on a research grant had: she was the patient. She knew exactly what the device needed to do because she needed it to do those things, every day, in her actual life.

She started with off-the-shelf components — sensors available through electronics hobby suppliers, open-source code bases designed for wearable projects, a used 3D printer she bought secondhand from a college student in her neighborhood. The early prototypes were ugly and unreliable and she wore them anyway, because even imperfect data was better than none.

"The medical establishment designs for the average patient in a controlled environment," she said in a 2021 interview. "I was designing for one specific patient in an uncontrolled environment. That's a completely different problem."

It took her three years of iteration to produce something she would have been comfortable describing as functional. During that time, she connected with a small online community of POTS patients who had been following her work on a patient forum. Several of them started testing early versions and sending her feedback. The device was being refined by its users before it had ever entered a clinical setting — a development process that looked nothing like how medical devices are supposed to be built, and worked better because of it.

What the Patient Knew That the Doctor Didn't

The insight at the core of Kreps's device wasn't technical. It was experiential. She knew — from eleven years of living in her body — that the most dangerous moments for a POTS patient aren't dramatic. They're transitional. The thirty seconds between lying down and standing. The moment after a meal. The slow accumulation of standing time over a day.

Existing monitoring tools were built around events: a spike, a crash, a measurable episode. Her device was built around drift — the gradual physiological shifts that precede an episode and, if caught early enough, can be interrupted. It wasn't smarter than the clinical tools. It was differently smart, informed by a kind of knowledge that doesn't show up in research papers.

In 2019, she filed a patent. In 2020, she partnered with a small medical technology company in Minneapolis to bring the device through FDA clearance. In 2022, it became commercially available.

The clinical reception was cautious, then curious, then genuinely interested. A cardiologist at a major academic medical center who began recommending it to her POTS patients described the device as solving a problem she hadn't known how to articulate. "We knew patients needed continuous data," she said. "We didn't know how to get it in a form they could actually use in their lives. Sarah figured that out because she was living the problem."

The Outsider Advantage

There is a version of this story that frames Kreps as an exception — the rare patient brilliant enough to engineer her way out of a medical system that failed her. That framing is both flattering and wrong. Kreps is not exceptional in her intelligence. She is exceptional in her persistence, and in her refusal to accept that the absence of a solution meant a solution didn't exist.

What she had that the medical establishment lacked wasn't technical skill. It was motivation that no grant cycle could manufacture. She wasn't solving an interesting research problem. She was solving the problem of her own life, and that urgency produced a clarity of purpose that academic medicine, for all its rigor, rarely achieves.

She was also unencumbered by the assumptions that shape how medical devices get designed. She didn't know what wasn't possible, so she didn't rule it out. She didn't know which approaches were considered inelegant, so she tried them anyway. She didn't have a mentor telling her to stay in her lane, because she hadn't known there was a lane.

The device now has several thousand users, most of them people who, like Kreps, spent years being told to just learn to live with it. Most of them are living with it differently now — with data, with warning, with a little more control over the days their bodies had been quietly stealing from them.

She built it in a spare bedroom. She built it because she had no other option. And it turned out that having no other option was exactly the right qualification for the job.