As I am sure you know, ANSYS general-purpose CFD codes are applied across such diverse industries as off-road (construction) vehicles, alternative energy, and oil and gas. This requires us to develop software that meets the modeling needs of the world’s largest user-base of engineering simulation. Which means our code can’t be everything to everyone. That is why we provide users with the ability to incorporate their own industry-specific capabilities. This level of openness that creates the opportunity for our users to implement their own cutting edge physics. This post will talk about how general-purpose CFD tools can be customized to model blood damage in medical devices.
But giving everyone the opportunity to become a developer doesn’t come without risk. Of primary concern is the potential to introduce errors into the simulation output via errors in the user code. These types of errors can lead to improper decisions about device performance that could lead to failure or a lack of performance during testing, or, even worse, after the product is released.
Highlighting the importance of this issue, ANSYS co-authored a paper with the US FDA summarizing the need for verification, which is the process of identifying and removing errors in computational code. We took advantage of our combined expertise in blood-damage modeling to develop benchmark examples that utilize the hemolysis index equation:
HI(%) = α*(τ)^β*(t)^γ
The hemolysis index, commonly referred to as HI, is an empirical correlation that is used to predict the effects of shear stress (τ) and exposure time (t) on blood damage in blood-contacting devices. The coefficients α, β, and γ are determined through bench-top testing of hemolysis in controlled shear flow environments. HI is typically estimated for one pass through a device and then extrapolated to multiple passes.
Integrating the HI relation in a computed flow field provides a numerical prediction of blood damage. The integration can be performed using either particle tracking or scalar transport approaches. Both of which are discussed and analyzed in the recent publication.
ANSYS continues to develop their expertise in this area by leading the MDIC Blood Damage Working Group. The team is comprised of scientists and engineers from industry, regulatory, and industry service providers. The goal of this group is to develop bench-top models that can help us understand how flow and other factors affect hemolysis and thrombosis in medical devices. The results of these investigations can then be used to develop “regulatory-grade” blood damage models, whose credibility is formally established for specified applications.
So goodbye for now, but expect me to say HI to you again in the near future.
Learn more at our Healthcare Industry Webcast Series
ANSYS hosts a monthly healthcare webinar series, where key healthcare industry solutions are presented by industry experts. These webinars take place on the 2nd Tuesday of each month at 11 am Eastern Time U.S. Please see this page for recordings of past webinars and to register for upcoming webinars.
ANSYS Advantage articles by Ension on blood pumps, Cardiovascular Engineering and Change of Heart articles make for great additional reading on how ANSYS users apply our CFD technology to cardiovascular device development.