Our Changing World: New tech aimed at improving heart health at home

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The workshop at the Institute of Biomedical Technologies (IBTech) at Auckland University of Technology (AUT) looks exactly as you would expect a workshop to look. Shelves with tools and spare parts, a work bench with a drill press and other benches with lamps and half-built projects. A 3D printer whirrs away between the shelves on one side of the room.

This is where some of the products aimed at improving healthcare across the country are developed and refined.

Blood pressure monitoring

From the workshop, the prototype is tested in the clinical room, a space with a hospital feel. There Dr Tet Chuan Lee, a senior lecturer in mechanical engineering at AUT, sets up a prototype blood pressure monitoring device. About the size of a shoebox, the back holds all the mechanics and electronics. Poking out of the front is a syringe filled with water which is attached to a small cuff that can slip over the end of a finger.

The prototype cuff looks like it is made from a balloon. It is actually made from the tip of a glove.

"When you're doing this kind of thing, you're wanting to try things very quickly," says Tet Chuan.

"So you just work out, okay, what's the quickest way I can kind of do that."

The device is one of several being developed at IBTech, where researchers are working on ways to measure heart rhythm and blood pressure more easily, more comfortably and more accurately outside hospitals and clinics.

The goal is to help people manage heart conditions at home, detect early warning signs and reduce pressure on health services.

"Cardiovascular disease is world-wide the biggest killer," Professor Andrew Lowe, director of IBTech, tells Our Changing World.

"Just under a third of the population will have a cardiovascular event and as we age as a population, it's getting worse and worse."

The future of blood pressure monitoring

Andrew says current techniques for measuring blood pressure make a lot of assumptions about the patient, such as arm size, muscle vs fat composition, and stiffness of the arteries.

These things affect the way pressure gets from inside the artery to the arm where it is usually being measured.

And most blood pressure devices these days use a population average to estimate what's going on between the heart and the surface of the arm.

That's great if you're close to the population average, says Andrew. "But if you're not, that tends to cause quite a large discrepancy in blood pressure and unfortunately, that discrepancy happens most when people are sick, because at that point they're least like the normal average person."

So one of the projects involves developing sensing technology which can model an individual, rather than making assumptions based on population averages.

The prototype

Tet Chuan's prototype involves taking a blood pressure reading from the finger rather than the arm. Water is used instead of air because it does not compress, which can improve the signal.

While the pressure is much like you would feel from a normal arm cuff, it is less uncomfortable and over very quickly.

Tet Chaun says the device increases pressure while measuring small oscillations in the pressure waveform. Those measurements can then be used to build an individualised model of the tissue and pressure response.

He says the technology could be useful not only for taking a blood pressure reading, but for tracking the actual shape of the oscillation between the systolic and diastolic readings.

"The actual shape of how it goes between those values potentially carries quite a lot of information", says Tet Chuan. "But there's not really a good way of measuring that non-invasively."

If you're in hospital and not sick enough to have an arterial catheter inserted, but doctors want to closely monitor your blood pressure, the current option is to take frequent arm cuff readings. That doesn't make for a restful time.

But Tet Chuan says the new device could do more rapid measurements more frequently, every 15 seconds or so, or it could potentially be calibrated with one big inflation and then be left a little less inflated and take continuous readings.

"If this works, this will be probably one of the first new ways of measuring blood pressure since about 1960," says Professor Lowe.

He says there are competing technologies in the field, including approaches based heavily on artificial intelligence, but the AUT team believes its physics-based approach has a strong chance of success.

Sit back, relax and have your heartbeat monitored

PhD candidate Matin Khalili demonstrates another prototype: an office chair fitted with sensors.

Two small round electrodes are attached to the back of the chair, while a soft strip of fabric on the seat acts as a grounding electrode. All it takes to get a reading, is for someone to sit down in the chair.

"We developed a system with three capacitive electrodes that can measure your ECG from your back, your chest, or your hand, or even in a chair," says Matin.

"I think that's ideal for elderly care or even in waiting areas."

Heart arrhythmias, such as atrial fibrillation where the heartbeat flutters, are associated with strokes. The risk is there whether the unusual rhythm is occurring continually or only occasionally.

"Actually, the abnormal rhythms for about one third of people, they're not continuous," says Andrew.

Arrhythmias are diagnosed using electrocardiograms (ECGs), which measure the electrical impulse that causes the heart to beat. The challenge is that arrhythmias are not always happening when someone is being monitored.

Currently, people with suspected arrhythmias may be sent home with a Holter monitor that records ECG data for 24 or 48 hours. But Matin's device is being designed for longer-term and more comfortable monitoring.

The flaw with capacitive electrodes though, is they not only capture electrical heart impulses, but other "noise" too. If someone shifts in the chair, moves their arm or changes posture, the ECG can be distorted by motion artefact which makes the signal harder to interpret.

Matin's research focuses on measuring both the ECG and the noise at the same time, then removing the noise from the signal to leave a clear reading.

If after removing the noise, you are left with no signal - at least you know that motion artifact was the issue.

Andrew says for patients, the benefit of this sort of device could be longer monitoring, at home, without adhesive electrodes, which can irritate the skin.

"If somebody wears it for a week, that is likely to catch about 80 or 90 percent of the arrhythmias, whereas if it's 24 hours or 48 hours, it's maybe 60 percent," Andrew says.

"So there's quite a big diagnostic benefit there."

The same information could also help people understand what may be triggering their arrhythmias, such as sleep position or exercise.

From workshop to the home

Andrew says both the arrhythmia monitoring and blood pressure projects have government support to begin clinical trials.

The long-term hope is that people with heart conditions could be monitored more reliably at home, while clinicians receive better information to guide care.

"If you can support somebody with good management of heart failure in the home, you can delay hospitalisation and reduce the risk of death," Lowe says.

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