Thanks for taking the time to go through my project Alejandro!
- How do you adjust the length of the nasal pillows strap?
One of the main ideas behind my design is that the machine and straps are tailored to the individual. When a person is prescribed a CPAP machine they usually go into a sleep center, try on a few masks and take one home not knowing how it's going to treat them when they try to use it at home. I wanted to change this experience so instead of going in the sleep center to pick up your machine and mask you would go in to be fitted for your machine. This would mean 3D scanning the head, and then printing the head cushion and nasal pillows. Those files would stay with the user for good and be used for future replacement parts (Currently, companies send out an abundance of replacement parts every month, many users I talked with have boxes full of these pieces)
As far as the strapping I intended for it to be fit for you as well during the initial experience. Both straps are designed to be stretched over your head and nose, so I didn't intend for the users to be able to adjust the strapping, rather it would be fitted and the elasticity of the material would gently press the pillows against the nose. This decision came from finding a large community of users deconstructing their masks and using panty hose for strapping. The consensus was that by using a stretch material with a larger width it created less pressure points than current thinner strapping. One of the complaints with current straps is that they leave creases on the user's face for a long time. My mom uses one of these masks and some days those creases don't disappear until 3 or 4 PM. The other comment about using a stretch material for the nasal pillows was that it secured them in place fine and created a much more comfortable sensation.
- How heavy is the PAP machine? Would it move sideways when you are sleeping? Is there a way to prevent that? Would it be possible to redesign the PAP machine and make it a bit thinner?
The PAP machine weighs just over 8 ounces (half a pound). This came from research on current CPAP Centrifugal blowers used in standard PAP machines. I referenced one of the most quiet blowers on the market for size dimensions. A key insight into my research was that by moving the blower closer to the nasal pillows and drastically reducing the length of tubing the machine would run at a much lower speed which means a quieter experience and less dampening materials needed in the housing. I verified that this is a logical assumption with a few professionals involved in flow dynamics and these types of blowers. I did bring up the question about reducing the size of the blower, and we agreed that it could potentially use an even smaller blower, however, the larger the blower the quieter it will run. So by shrinking the size, it would run harder and louder and the only way to verify how small is too loud would be to do a whole lot of testing. I felt that shrinking the blower without any hard evidence on how small it could go would be dishonest and misleading.
As far as movement on the top of the head: I tested many strap iterations, such as a horizontal strapping method. The horizontal strap proved to be a lot worse for people who slept on their back as it wanted to fall right off the back of the head. What I found while testing my mockups was that when the PAP machine was in contact with the pillow it was entirely weightless, you would have no idea that it was there. So I placed the blower towards the back of the head as it served as a good axis of rotation for any sleeping position and had more contact to be supported by the user's pillow.
- Could there be a way to adjust the position of the PAP machine? Some people sleep on their back, while others sleep sideways. I believe a little adjustment there could be interesting.
I'll look into this some more, thanks for the suggestion!
Other than that, where you explain the struggle with this kind of machine, I'd add a graphic explaining better the weak points. Maybe leaving the images as proof, but not the main source of information.
Last thing, in order to improve grip, most head mounts have a silicone stripes on the inner part. It's just a detail, but it really helps. This is an example:
This could be interesting, I'll look into it!