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Improve Auto-Injector Design with Task Analysis
- 1. The Re-design of a Betaseron Injector
- 2. Problem: A non-user friendly medical device
- 3. We used Task Analysis to ensure that any changes made to the injector would not create further problems. TASK ANALYSIS RE-DESIGN
- 4. “Task analysis is defined as any process of assessing what a user does and why, step by step.” (BIOE 2580 Course Notes)
- 5. We video recorded 6 people to study the sequence of steps necessary to use the product.
- 6. 4 females, 2 males Within the ages of 12 – 40 years old All of the users were unfamiliar with auto-injectors except for one subject who takes daily insulin doses.
- 7. People made several mistakes They all made the same mistakes
- 8. Where to place the syringe?
- 9. Correct placement of syringe How people were doing it
- 10. The blue cap was left attached in the syringe assembly.
- 11. Several small errors leave the user wondering if things have been done correctly or not. That causes unnecessary stress, feelings of uncertainty, confusion and frustration. It is always a long tedious process for experienced users.
- 12. How to push the button? At first attempt user implemented a downward pulling of the button rather than pushing it.
- 13. “Now, holding the blue Mixject adapter cap, connect the syringe to the open end of the adapter by carefully turning the syringe clockwise until the two pieces are connected. It shouldn’t take much force. The syringe system is now assembled.” LONG PARAGRAPHS POOR RESULTS
- 14. Do people tend to assume things are done one way or the other instead of how they are really supposed to be done?
- 16. Do people fully read long paragraphs in instruction manuals?
- 17. We should… BUT what if the user does not do it? Is the injection going to be delivered safely? NO ✗ ✗
- 18. ✔
- 20. Changes to the Reconstitution Process & Instruction Manual
- 22. Original Design
- 23. Twist and push 1) Twist 2) Push
- 24. Overview
- 33. Pushes the needle into the skin (Penetration Spring) Contact ring attached to Penetration Spring (Blue Ring) Pushes piston of syringe, delivers medicine (Injection Spring) Holds Injection Spring compressed (Light Blue Piece)Purple Ring: -Pushes Green ring down -Pushes Light Blue Piece Green Ring: Holds Syringe Purple Ring Springs: Store Energy Smallest Springs: Weaker than the friction coefficient of skin
- 34. Safety Mechanism, The only feature kept from original You cannot push the button if you did not mean to.
- 36. The button Has been pressed
- 37. The ring has been released. Notice the springs In their relaxed position
- 40. NOT TO SCALE!! The springs have now been compressed inserting the needle and storing energy
- 41. The blue ring has already come to a relaxed position Sky blue piece is pushed triggering injection Springs rise with the Stored energy
- 48. Injection Spring is Released. Injection proceeds
- 51. The piston of the Syringe is pushed by the yellow piece
- 52. Insertion of needle Injection NOT TO SCALE
- 53. The purple feature loads the springs making the injector Reusable.
- 54. Twist and push 1) Twist 2) Push
- 60. SEPARATE MECHANISMS WILL ALLOW CONTROL OF THE PENETRATION FORCE AND CONTROL OVER THE INJECTION RATE, MAKING THE INJECTION LESS PAINFUL.
- 61. Changes to the Reconstitution Process & Instruction Manual
Editor's Notes
- Now I can return to explain our sketch.
- It evolved from a hand drawing sketch to a computer sketch. I will start by naming the parts of our design: That spring pushes the needle into the skin, the names appear inside the parenthesis The spring is attached to a blue ring, the blue ring makes contact with the purple ring Then we have the injection spring it pushes the piston of the syringe when released There’s also a piece which hold the red injection spring in place, that’s the light blue piece When the purple ring is pushed by the blue ring it pushes the green ring down and then pushes the light blue piece The rings attached to the purple ring store energy and act as a resistance force against the blue ring And the smallest springs hold the green ring and the syringe and are weaker than the friction coefficient of the skin
- The safety mechanism is the only feature that we kept form the original design. You have to push the injector down, when you do that the little red piece inside the circle will come down and you are able to press the button. So you cannot push the button if you did not mean to.
- After the button is pushed, the blue ring is free Pay attention to the button springs, they will be compressed. You will see it in action.
- Obviously the spring is not to scale. I did not have the appropriate software. Every time I tried to enlarge the spring vertically it would become wider at the same time and I couldn’t find a way to fix that. Anyways you can notice the springs have been compressed. When this happens the needle goes into the skin and at the same time the springs store energy from the spring of the blue ring and they also provide resistance to the penetration spring making the needle not to go very strong.
- The green ring remains compressed while the purple ring rises with the stored potential energy of its springs. When that happens the purple provides a push to the light blue piece that moves it.
- That push frees the injection spring.
- Again the red spring is not to scale, it becomes wider and at the same larger.
- When the red spring is released the yellow part pushes the piston of the syringe.
- In summary this is what happens.
- SPRING LIVE DEMONSTRATION. “The purple feature will make the job”