The Design History File (DHF)

Manufacturers of medical devices are required by the FDA to maintain a Design History File (DHF).  The DHF is a complete history of the device from inception through medical trials and all the way to its present design configuration.  Understanding the DHF requirements will be of great assistance to the independent inventor when he or she approaches potential device manufacturers.

The design process is very dynamic and one of the most important aspects of a device life cycle.  This is especially true given the requirements of the FDA for medical device manufacturing.  Many times, the multitude of steps between “I have a good idea” and “first unit sold” is complex and misunderstood.  Quality, effectiveness, safety, and customer satisfaction are established during the design stage.  Therefore, it is important to establish and maintain adequate control steps.  These steps make up the Design History File (DHF).

Imagine for a moment that an inventor has an idea for an adhesive bandage.  The DHF would contain the following entries:

• Design and development planning
  • Identifies people, activities, and responsibilities involved in the design process.  The people involved could be as small as you and your engineer neighbor, or as large as a Project Manager, Design Engineer, Manufacturing and Materials Management, the Legal Department., etc.
• Design Review
  • Documentation showing the design team members have performed reviews of design results at appropriate steps throughout the process. This review must be done by the people identified in the design and development plan, as well as an individual with no direct responsibility for the particular stage being reviewed.
• Design Input (what you want)
  • Specifically, what is the device?  This stage determines, in detail, what the design requirements are in relation to intended use.  Ambiguous or conflicting requirements (i.e., 3 pound device must be made out of 24K gold, but selling price must be under $5.00) must be dealt with at this stage. 
    • Example: Single use, disposable, absorbent strip for protecting minor wounds.  Must be flexible enough to wrap around non-uniform aspects of human anatomy.  A flesh tone color is ideal, but not required.  Packaging considerations should include individual as well as bulk (each, box, case).
• Design Output (what  you have)
  • Evaluation of concepts.  This can include review of concept drawings or of a concept model.  Include the acceptance criteria identified and used by the design team.
    • Example: Engineering drawing of the product, specification for the elastic strip,  specification for the adhesive, and information from prospective material suppliers on biocompatibility.
• Design Verification
  • Does what you have (Design Output) match what you determined you wanted (Design Input).
    • Example: Does the concept/specification/physical sample representing your design output give you the product you want to bring to market (i.e., do you have an adhesive strip bandage?),
• Design Validation
  • In defined operating conditions, on initial production units, does the device conform to user needs and intended uses?  Tests and clinical trials must be performed under actual or simulated use conditions.  Software validation (if any) and risk analysis should also be done at this time.
    • Example: Does the adhesive strip  work as intended?  Has it performed the way it should in it’s intended environment?  Are there risk factors that require changes or warnings (use in temperatures below freezing causes the adhesive to lose bond).
• Design Transfer
  • Has the device been successfully transferred from the design/development team to the manufacturing team/facility?
    • Example: Do the units coming off the actual production line (using normal processes, techniques, and machinery) match the verified/validated device?
• Design Changes
  • Documenting, reviewing, validating, and approving changes to the device after it has been transferred to manufacturing.

The Design History File (DHF) is a compilation of each of the items above, and will be a dynamic story of the evolution of the device (information will be added to the file anytime changes are made to the device).  This is a fluid and iterative process.  Depending on the project, design history files can resemble an encyclopedia.  This means that  it is perfectly acceptable to go from input to output and back to modify/redefine input based on what you have learned.  For example, during the output phase, unanticipated challenges could arise with procurement issues, process problems, or equipment constraints.  This may happen several times before you accept the design output and move on to verification.  These stages help avoid spending time and money in product development progressing to the design transfer stage before finding out manufacturing is unable to make the configuration as it is designed.  Ultimately, this process guides and refines product design to help ensure the end-user gets a quality device that performs as intended.

By understanding the value of the DHF, the independent inventor can increase the value of his or her invention to potential device manufacturers.  It is suggested that inventors take a few simple steps to document the evolution of their device. 

1. Maintain a design history log.  Document the steps and iterations that the idea went through.
2. Retain all relevant drawings and sketches.  Even simple and crude sketches can communicate the design process.
3. Retain any physical models or prototypes of the invention.
4. Annotated digital pictures are a great means to document the progress of a device.
5. Maintain a file of relevant websites, product literature and competing products.
6. Document the objectives of the design, and the features and attributes that make it unique.

In short, a little effort in compiling an informal device history will be of value to the device manufacturer as they begin the formal DHF process.  In addition, experience has shown that maintaining a basic device design history assists the inventor as well.  Often, inventors have found that the discipline of documenting their progress has been of great value in bringing focus to the inventive process.