I've been using a ResMed Air Sense 10 for over a year with the default auto setting 4 -20. The average pressure has been about 12. My previous machine was set by the sleep lab at 6.
Last week I bought a Z1 Auto for travelling and used it 4 nights. Overall, I am happy with the machine, not as quiet as the home unit, but quieter than the hotel HVAC and I slept as good as when home. However, the morning report said the pressure was only 4 with the auto set at the default 4 -20. Last night I raised the min to 6 and it started about 6.2, then dropped to 6.0 for most of the night.
I just downloaded the ResMes software (thanks, I wish I had it a long time ago) and got the detailed reports saying my median has been 10.6; 95% percentile was 13.2.
Also the Z1 only detected a total of 4 AHs over the 4 nights, 2, 1, 0 & 1, while the ResMed Says AHI is 1.3 or about 10 in an average 6 hours night.
Could the Z1 be defective?
WELCOME! to the forum.!
Much success to you with your CPAP therapy.
Each manufacture uses their own proprietary software and algorithms, there will always be a difference in each machine whether it be Resmed, Philips, F&P, or whatever. I have owned and used Auto machines from five different manufacturers. The Resmed always wants to go to a higher pressure than any of them because it's so sensitive to Flow Limitations, I actually have to limit the upper end pressure in the settings to keep it from going too high (higher pressure than I really need). My F&P Auto Icon never gets anywhere near my Resmed and I could leave the upper Limit wide open (20cm) and it never goes above 12cm whereas the Resmed would climb up around 15 or 16. My Z1 Auto stays even lower than my F&P Auto, as does my Transcend Auto.
You'll have to learn what your machines want to do and use your Sleep Test numbers as a reference point to set your lower and upper pressures where you want them. I think you are on the right track by increasing the lower pressure setting on your Z1, your Z1 is just never going to get up where it needs to be unless you force the pressure up where you need it by increasing the low end setting, as you are doing.
I think the Resmed is probably the most accurate and sophisticated in terms of its algorithm (although it can get too high in certain cases) so use your Resmed as the model to set up your Z1. Increase the low end of the pressure range on your Z1 so that it runs closer to the your average pressure that you get with the Resmed. I don't think your Z1 is defective, it just is an inferior auto algorithm - they haven't been in this business very long like a company such as Resmed or Philips, so although it's a nice size travel machine it just doesn't rival the big boys in sophistication. But you can force it to do what you want/need in terms of therapy pressure.