As healthcare technology becomes increasingly advanced, it more important than ever to ensure patient safety by regularly testing medical equipment.
Why test?
Hospital monitoring equipment plays a central role in the day-to-day working of any facility, so ensuring that this equipment is accurate through regular testing and calibration is a vital part of patient care.
We all know the disastrous results of faulty or inaccurate equipment: problems with patients can be missed or misread, and costly inquiries can ensue.
In fact, a British Medical Journal study found that one in four operating room errors are due to equipment problems – many of which could be avoided by simple device checks before surgery.
So while much of the industry’s focus is on innovations in healthcare equipment, it’s important to remember the test devices which interact with and safeguard this equipment.
(Credit: Rigel Medical)
How test devices work
There are many types of testing devices, from simple electrical safety analysers to more complex vital signs simulators. All perform the core function of putting healthcare equipment through its paces to ensure patient safety in real medical situations.
Electrical safety analysers are ideal for testing high volumes of medical and laboratory equipment which don’t require patient-lead testing, such as beds, hoists, infusion pumps, CPAPs and centrifuges.
One way to test medical equipment is by using a patient simulator, which mimics vital signs – such as heart-rate, body temperature, blood pressure, and respiration.
It obviously isn’t practical or reliable to test the accuracy of these monitors on patients or volunteers. A patient simulator device plugs directly into monitoring equipment and, through electrical signals, simulates various types of vital signs from electric cardiogram (ECG) to invasive blood pressure (IBP).
All of these tests can be performed relatively fast by in-house engineers, independent service operators, or by the manufacturer’s own service engineers under the hospital’s contract.
What’s “under the hood”
Human vital signs are complex signals, particularly when we’re talking about ECG waves as these are very small.
At the heart of a good patient simulator design is a solid, low-noise analogue circuit design, with excellent isolation from sources of 50/60Hz mains-frequency and other electrical noise.
Because human vital signs vary just as much as people do, there is an incredible array of variables and parameters to consider. In the case of ECG, first there is the amplitude of the waveform – on the order of 0.5 – 5mV. To reproduce the smallest ECG waveforms with the required accuracy, a resolution of around 1uV is needed.
There is also the rate of the waveform. While typical ECG waveforms may be limited to the range 30-300bpm, a patient simulator can often output performance waves at anywhere from 0.05 to 100Hz. Additionally, simulating distinctly non-biological sharp-edged Pacer waveforms of around 100uS in width requires output frequencies on the order of 10’s of kilohertz or more.
There are other parameters too, such as ST elevation and adult/neonatal selection, along with a host of different arrhythmia waveforms. That is not even taking into account respiration, temperature and invasive blood pressure simulations, each of which needs its own output. It is also in addition to the nine independent outputs required for correct simulation of a 12-lead ECG. This means a powerful processor is needed to store, process and output these signals – typically a 32-bit microcontroller with some DSP capability.
The on-board software to make all of this work includes a very complex design, but the product needs to be as simple as possible for the operator to use. And as any design engineer will tell you, achieving true simplicity is not a trivial task.
Making the user interface as simple as possible requires a huge amount of thought and planning from the start. A product should feel intuitive and easy to use without referring to the documentation. Let’s face it, reading the manual is a niche activity. Buttons should be in just the right place to fall under the user’s fingers. The more often a task is carried out, the fewer interactions should be required to do it. You should present exactly the right amount of information to the user, and no more.
(Credit: Rigel Medical)
For our latest patient simulator design, the PatSim200, we took a clean-sheet approach. We spent countless hours shadowing biomeds to understand what they really wanted from a vital signs simulator.
From that knowledge, we designed a completely new enclosure from the ground up. We made it robust, ergonomic, and portable. We included a rechargeable battery to help cut running costs and help the environment.
Using a micro-USB connector for charging makes recharging easy and familiar, too.
Front and center we put a large color display, with a home menu that displays all the currently running vital sign parameters – no hopping around frustrating menus. We even skipped the traditional splash image so the user can get straight to work.
Next, we analysed biomed workflows to eliminate unnecessary operations and button presses. This helped us to craft a consistent and intuitive user interface that makes the job quicker, which was a key priority for our users.
The technology in practice
The way users interact with test devices varies. Designers and engineers usually don’t see their products in use on the hospital floor, but it’s important to be aware of how the device works in the real world.
Are there aspects of your design which could be prone to obsolescence? Will it be obvious to users if your product becomes inaccurate or faulty? Does it require external testing and calibration? All of these factors can have implications for patient safety.
Good electrical safety analysers and patient simulators will be compatible with most equipment in the field – assuming you can lay your hands on the right leads for the job. Plus in-house and external engineers are experts in their field and they should be able to advise on when equipment needs to be replaced.
The good news is that patient simulators and other testing technology are at their most advanced and cost effective ever – which is changing hospital managers’ approach to testing. The latest innovations in test devices are around making the products easier and faster to use, as well as more portable, which will help to encourage regular testing of medical equipment.
Because today’s market-leading test devices are so quick and easy to use, engineers can save minutes on every test – which over the course of a year can really add up.
The future of testing
What does the future hold for monitor testing? Hopefully in the future, testing of hospital equipment will be more connected and data-driven, meaning that testing can be more responsive, with results uploaded and processed in real-time.
But until then, engineers and product designers will have to continue leading the way in enabling the regular testing of healthcare equipment.
In the biomed field, we know that engineers and their test equipment don’t save lives, but it is a key part of ensuring quality patient care.
