CapstoneEngineerMagazineFall2026 - Flipbook - Page 11
presence of clothing under the cuff, arm positioning or the
size of the cuff, can throw off the readings.
Incorrectly sized cuffs can cause erroneous readings in
both directions — if the cuff is too large, the sensor can
provide a falsely low reading, and if it’s too small, it can
provide a falsely high reading. Ultimately, this can result in
a patient being misdiagnosed or prescribed medication that
their body doesn’t need, potentially causing confusion among
practitioners or health problems down the line.
Dr. Amanda Koh, an associate professor and honors
program coordinator for the department of chemical
and biological engineering, is currently working on a research
project that will provide insight into blood pressure cuff
accuracy, with the end goal of creating a universal blood
pressure cuff that is capable of capturing an accurate reading
regardless of arm size.
The idea for this research originated when Koh had a
conversation with Dr. Keri Barron of the Capstone College of
Nursing, who has an interest in cardiovascular health in rural
communities.
“If we are using this as a foundational measure to track
whether a patient’s blood pressure is going in the direction
we want it to go in, and the cuff that we choose is inaccurate,
then that can impact the healthcare provider’s effectiveness,”
Barron said.
Based on this conversation, Koh’s initial goal was to
develop a universal blood pressure cuff that could accurately
measure the blood pressure of an individual regardless of the
size of their arm. As Koh’s research focuses on soft materials
used in creating sensors, including pressure sensors, which
are similar to those in blood pressure cuffs, it was a natural
project for her lab group to pursue.
As Koh began to research, she realized one key detail that
is missing from the literature: although we know that the
size of the cuff matters as it pertains to accuracy, no research
study has yet answered why the size of the cuff impacts the
reading. To take a blood pressure reading, the cuff constricts
blood 昀氀ow around the upper arm, essentially closing the
brachial artery, which sits on the front of the bicep and
extends from just below the armpit to the elbow. Once the
昀氀ow within the artery is stopped, it is slowly reopened,
measuring the systolic and diastolic blood pressures as the
昀氀ow restarts.
“So, one would think that as long as the cuff can compress
the artery suf昀椀ciently, that should work. And yet, it doesn’t,”
Koh said. “In order to make a device that solves this problem,
I 昀椀rst need to know what the problem is. We know what the
challenge is, but we don’t know what the biological source of
the challenge is.”
Koh and her lab group are currently working with three
model arms made of silicone rubber in various sizes — small,
medium and large — a few of which they cast from human
participants using machinery in The Cube, the College’s
makerspace that houses state-of-the-art manufacturing
equipment.
The model arms are created so that a small silicone
tube, mimicking an artery, runs through the length of the
model. Both the arm and the tube inside have the same
ABOVE: A size small blood pressure cuff is secured around a
model arm that Dr. Koh’s group cast in The Cube, the College’s
makerspace.
stiffness as a real human arm and artery to serve as a realistic
biological model.
Using a peristaltic pump to mimic the heart’s movement
of blood throughout the body, the researchers 昀氀ow water
with 昀氀uorescent particles through the tube as a camera
positioned within the model arm captures how the particles
act as the cuff compresses and releases.
For each of the permutations of the set — small arm with
small cuff, small arm with medium cuff, small arm with
large cuff, and so on — the researchers observe the particles’
behavior in every correct and incorrect pairing.
In a separate set of experiments, the tubing is 昀椀lled
with a polymer and cured while the arm is being compressed
by the cuff. After curing, the cuff is released, leaving the
researchers with a physical representation of how the artery
was obstructed by the compression of the cuff. Using slices of
the polymer at different placements along the tube, Koh and
her team are comparing how the compression appears at the
beginning of the cuff and shortly after the cuff ends to see
what characteristics might change in a correctly sized cuff
versus an incorrectly sized cuff.
“Based on our data collection, there is a huge difference,
particularly in the occlusion, between the correct size and
the incorrect size,” Koh said. “But the goal here is to look
at what’s happening in situ when you have model systems
given that we know that it’s incorrect. If we see a pattern
where the correctly sized [cuffs] do one thing and the
incorrectly sized do another, then that’s the problem that
we have to solve.”
The next steps for Koh’s group are to build a standard
blood pressure cuff that is “MRI invisible,” meaning
it contains no metals, to measure a human participant’s blood
pressure while they undergo an MRI scan. This will allow Koh
to visualize what the blood 昀氀ow looks like in a real human
arm, allowing for greater understanding of 昀氀ow as she drafts
designs for the universal blood pressure cuff.
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