A few  more things. Assuming you have a sleep study and need a cpap machine.

If you have a mustache you might do better with nose pillows rather than a mask.

My new machines are I think are Bi-pap. Both are Remstar's and I think the older one is a Auto M-series A-Flex. I think the other is similar but just a newer model.

Old or simple machines the pressure was set at one pressure. Period. You inhaled with the assistance of this pressure and you also exhaled against the same pressure. Modern higher end machines are smart machines. The pressure will adjust automatically to your needs. It will likely reduce when you roll on your side and increase while on the back. Technically over several weeks a high end machine computer will memorize your needs and adjust automatically almost instantly as you change positions or depth of sleep. They have memory your medical professional can analyze (although I have never taken my memory card out of either current machine). I say technically because I have found I need to limit my high reading or I will wake up sometimes "pumped up" with some air in my stomach. Machine manuals do not tell you how to adjust the machine - of course you are supposed to let a medical professional do that. My experience is I have more experience than some of the people that are supposed to know how to adjust the machine. There are on line discussion groups that will tell you the secret two keys to push to get into the adjustment mode for medical professionals. In the beginning, you need the "professional help" even though my experience is they are extremely limited in their knowledge of the machines. But in the beginning you need some help and guidance. After a few years you will probably have figured it out if you have any interest at all.

My newest machine is probably 10 years old. Back at that time I checked with my local hospital owned medical device store. They checked with my insurance and yes the insurance would rent it for a year (and pay the rental payments) then I could pay the co-pay and own it. They gave me a price for my co-pay. It was a very basic manually pressure set machine (like my original one). I checked on line and could buy two or three steps up to an auto machine and pay the total cost for only a few bucks more. I said phooey on the insurance. Now maybe the cheapest ones are auto flex, I don't know.

So what is auto flex? First off the machine adjust automatically to your pressure needs. Plus the one I have automatically drops pressure when you exhale, making the machine feel much more natural in the breathing process. Plus it is auto on and off. I take the headgear off for whatever reason, within about 20 seconds the machine shuts off. Put it back on, within the second breath is is auto back on. Really nice. Since losing weight sometimes I will sleep on my side without it for a while. turning on and off automatically is nice. The standard ones back then did not. The higher end ones also have a ramp feature (remember this is 10 year old info - they may all have that now). When they start up while you are still awake they start at a lower (programmable) pressure. For someone not used to a cpap this can help get to sleep more naturally. Then they ramp up the pressure as needed as you fall asleep. But probably the biggest comfort feature is that it drops the pressure drastically as you exhale.

There is probably more but that is what I can think of at this time. Getting a comfortable headgear is a must and there is where a professional in a walk in store can really be of benefit. I have used several different headgears over the years and the current one I have I really like. If you have a mustache it is very hard to get an air seal around the mustache hair. This I know. It requires cinching them down so tight they are uncomfortable. Or use something slimy like Vaseline to help seal. And a leaky mask does not lead to good sleep between the noise and discomfort. I personally use a head gear with nose pillows, but they have their own peculiarities. They do solve the mustache hair leaking problem though.

Modern machines are very quiet. The ones that auto adjust keep the blowing air out the exhaust hole to a minimum. If you have a super sensitive wife it could be a problem. If you have one that is concerned about your health (and low blood oxygen and lack of sleep CAN lead to very bad health problems) probably not. There are workarounds to any such problems.

I'm absolutely no expert. But I have been using multiple machines and headgear for quite some time. My wife also has one and uses it occasionally. But since losing weight she does not usually need it and does not travel with one like I do. It definitely helped her and her snoring back when she was heavier. She no longer has that problem thanks to a ketogenic diet  we both started four and a half years ago.

Hope some of this helps. If not you maybe some other AgTalk reader.