Berlin Heart: enhancing life-critical testing of paediatric cardiac equipment
Author : Brad Armstrong | Director of Marketing Content & Customer Journey | NI
01 August 2021
NI_EXCOR_Berlin Heart_T&M_case study
German MedTech company, Berlin Heart develops & produces innovative ventricular assist devices (artificial heart pumps) for mechanical circulatory support of patients with end-stage heart failure. Through its EXCOR® Adult & EXCOR® Pediatric product lines, it is the only company in the world offering systems that can support patients of every age & size, from newborn babies all the way to fully-grown adults.
This case study was originally featured in the August 2021 issue of EPDT magazine [read the digital issue]. And sign up to receive your own copy each month.
In this case study, Brad Armstrong, Director of Marketing Content & Customer Journey at software-centric, computer-based test & measurement firm, NI tells the story of how it helped develop a robust, accurate and reliably repeatable measurement & control system to enhance both product development and verification testing of these critical systems…
EXCOR Pediatric is a mechanical, pulsatile circulatory support system (paracorporeal ventricular assist device or VAD) that is used for short to long-term support of the ventricular pumping function. It is used for children with life-threatening heart failure, after all other options have been exhausted, bridging the patient to recovery or until a transplant can be performed.
However, the system is complex and testing it manually involves a significant amount of effort, due to the large number of steps involved. There is also a risk that human operators could mis-measure or even entirely miss important steps, allowing a less-than-perfect VAD to be released to a care facility, with potentially catastrophic consequences.
When looking to develop an automated test system to mitigate these risks, Berlin Heart selected T&M firm, NI because they already had a long history with the company and had confidence that its products were robust and capable of providing the accurate and repeatable measurement and control the system demanded.
NI were challenged to deliver an automated test stand for use in the development and verification of the EXCOR® Active control software that would be responsible for supporting the patient’s circulation. To do this, the test stand had to physically simulate pressures analogous to the systolic and diastolic pressures that form a blood pressure measurement, including generating extreme pressures to simulate an alarm condition.
Project goals included improving the repeatability, robustness, accuracy and time taken for tests, allowing for earlier detection of errors, faster software verification and a more robust end product. In working towards these goals, NI identified the need to develop a measurement and control system that would grow with the demands of the development process, as well as being robust enough to be used for long-term re-verification of new versions of the software.
The anatomy of the test stand
Multiple NI products were selected to meet the current measurement and control needs, as well as providing expansion capabilities for the future.
The NI 9263 analogue output module controls proportional valves that set pressures to simulate the systolic and diastolic pressures seen in the implantation of the VAD, while the NI 9205 analogue input module monitors pressure sensors that measure these pressures. An NI 9481 4-channel SPST relay module controls solenoid valves to simulate errors, such as pneumatic leakages and blockages.
All of these modules are housed in a cDAQ-9174 CompactDAQ chassis, which allows communication with a laptop via USB. NI’s NIDAQmx C API provides a software interface on the laptop to control the NI modules, based upon automated test scripts designed for development and verification tests.
Challenges & benefits of the new test stand
NI_EXCOR_Berlin Heart_T&M_case study_The test stand
The biggest challenge was scaling down from an adult version, as the mechanical valves were causing clots and needed to be redesigned to be trileaflet – mimicking the aortic valve. Also, the pneumatic system requires repetitive compressor checks running at 150bmp for an hour. The test stand overlays each pressure waveform to create a density plot and checks the variance to ensure that each compressor works all the time, every time.
Following development of the test stand, testing effort was greatly reduced, by around 75%. Also, test precision and repeatability were significantly improved, saving time lost to testing errors and allowing for faster implementation and verification of development software and hardware changes.
It was estimated that prior to implementing the new test stand, manual software verification would require around four weeks. With the new automated test stand, this has reduced to just one week, with the potential for further improvement as the system evolves.
The development of the test stand was challenging, not least because of the criticality of the VAD that was to be tested. However, the modular approach taken has provided a future-proof solution, while the robustness of the hardware ensures that the test stand is suited to both development and long-term verification testing.
Berlin Heart have found that the new test stand allows for rapid detection of issues in the development phase, providing safety-critical feedback much earlier than with manual testing. In turn, this results in faster verification and integration of tested software changes, allowing it to bring these potentially life-saving enhancements to patients more quickly than before.
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