Delivering on a promise

Medical device designers know that their inventions will be tested, measured, and re-tested before they ever become commercialized – and that analysis will be driven by the juxtaposition of three priorities: marketing, technology, and regulatory requirements.

A need for new medical technology is identified by the market and instigated by needs and opportunities revealed in medical challenges, treatment, and surgical advancements. Sometimes adverse events – such as fatal infections transmitted by contaminated, reusable endoscopes – expose the need for better technology. Once a demand is recognized, engineers can develop new solutions and move technology forward in the interest of improved public health and medical outcomes.
 

Designing devices for FDA harmony

Designs for new medical devices follow a rigorous path before they are submitted to global regulatory bodies and the Food and Drug Administration for PMA or 510(k) approval. Testing and measurement for what the FDA refers to as “validation and verification” is a critical part of the process. The new device must be proven to meet accepted standards and repeatably and reliably perform in accordance with its own marketing claims. The FDA reviews the results before giving its stamp of approval, ensuring that the product’s labeling is consistent with its demonstrated performance.

For device designers, the three disciplines comprise a three-legged stool supporting their work from start to finish. While developing a concept, engineers establish output specifications and devise design of experiments (DOEs) to test performance against those specs, then modify designs accordingly. Repeatability and reliability are the two guiding forces in testing. Specs must be met in repeatable scenarios, with a limited degree of variance; the test methods must stand up to reasonably expected variations in operators, tools, and environments, with repeatable results.
 

Benefits of a reliability block diagram

The testing and measurement process is created to demonstrate the device’s efficacy and safety. A reliability block diagram (RBD) is a commonly used tool to guide the process. An RBD is a drawing and calculation tool used to model complex systems. Incorporating a series of images (blocks) representing portions of a system, the RBD is used to calculate predicted failure rate, mean time between failures (MTBF), reliability, and other system parameters. Changes to design are reflected in the RBD diagram, where calculation results also change. This mapping process allows engineers and product managers to create appropriate specifications, testing and measurement protocols, and marketing claims that will guide the device’s final design and approval.

The structure of the reliability block diagram defines the logical interaction of failures within a system that are required to sustain its operation. It predicts reliability based on a calculation model, using standard literature and component documentation, where available. It may also document critical sub-assembly testing as well as system-level tests performed to fit anticipated uses for the device.

The RBD is a tool for analyzing potential component failures to help define a device’s specifications and instructions for use and maintenance. These failures may be independent or dependent upon one another, that is, one component failure may increase the likelihood of another. Statistical analysis quantifies these probabilities. The likelihood of component or system failures along a device’s expected useful lifetime is also calculated, sophisticated mathematics.

Dave Yavorski, VP of quality of Proven Process Medical Devices Inc., explains, “We work hand-in-hand with our customers to quantify and test for specified output requirements that meet combined goals for marketing, manufacturability, validation/verification, and regulatory approvals. We leverage our experience with the FDA to coach our clients and help them understand the required data outputs and reporting structure that support a robust DHR.”

A design history record (DHR) is submitted to the FDA and includes all testing documentation. Yavorski adds, “This is fundamental to the work we do every day and to the service we provide.”

Combined experience, engineering skills, and objective tools like the RBD are needed to build achievable metrics, and to scientifically test and document a product’s performance in meeting them. These practices are fundamental in an industry where, with sufficient oversight and proof of performance, innovation can bring enormous benefits.

Proven Process Medical Devices Inc.
www.provenprocess.com