Resmed S10 Fit Test: Does it matter?

So I'm new to CPAP. Finally got my mask, an F20 large, and my machine, an S10. This is my first night attempting to use it all. The machine has a fit test mode and, no matter what I do, I fail the test. However, I now have the mask on and it feels decent.

How much does the fit test matter and, if I need to loosen the mask to feel more comfortable and a little air leaks out, does that mean it won't work?

Which ResMed "S10" did you get? There are different models, and that affects the answer to your question.

If you have an AutoSet and pressure is set to factory default settings of 4-20 cmH2O, the fit test will be at 20 cmH2O and will probably not be relevant, assuming your machine doesn't raise the pressure that high during a night of therapy.

The fit test is really just a way to help you find a good mask tightness. It is certainly not required that you run the mask fit test (I may have run it four or five times in two years). I suggest just trying it for a night and seeing how much it leaks. Getting the right tightness of the straps is a balancing act between too tight and too loose. The machine can tolerate a certain amount of leaks without affecting your therapy. Leaks are more often a problem because of noise or the leak resulting in an uncomfortable flow of air against your face, eyes, etc.

While the machine will display a red "frowny" face if the leaks are too high, that is a pretty coarse evaluation. I do recommend putting an SD card in your machine and then using OSCAR to see how your therapy is going, how much air is leaking, etc.

Alternatively, you can set essentials to plus, and view whatever is available on the screen.
Depending on your machine--it could be plenty, or next to nothing.

Yes it matters and yes it can potentially affect the therapy/treatment in a negative manner depending on how bad the leak is.

Use available software to evaluate the leak in detail.

OSCAR https://www.sleepfiles.com/OSCAR/
http://www.apneaboard.com/wiki/index.ph ... stallation
http://www.apneaboard.com/wiki/index.ph ... rpretation