Watchpat data different then my CPAP machine

[Kramer]

I’m new to the group. I am a 53 year old male, 5 8 and about 200 pounds.  I take lot of high blood pressure medication.  I also have moderate right side heart failure,   I have been using CPAP since 8/19.  I have a ResMed aírsense 10 set with initial pressure of 6 min and 12 max.  On the myAir app I usually hit 100 With my ahi is usually under 1.  I thought I was good.  I switched to a new Sleep dr recently. My original sleep study I had ahi of 8 and the dr wanted me to take a new sleep study with the watchpat device.  I did and I also wore my CPAP.  The Sleep study came back with an ahi of 6 but during rem my ahi was almost 13.  Also my o2 level went under 90 foR almost 10 minutes.  Also new term for me Was rera which was quite high which I assume was not allowing me to get Into deep sleep.  The. Dr wants me to come in for a titration but due to COVID  I have to wait until they reopen.

My insurance is not good so I am wondering if I need to pay for titration.  I downloaded sleepyhead a couple of days ago.  I have been lurking on these boards and went in a changed my settings whereby min pressure is now 7 instead of 6 and epr is on 3 but only on ramp.  Last night was my first night sleeping with new settings and my machine said I had an ahi of 0 and my o2 never went below 92.  I know this Is only one night but still excited.  My questions are:

1:  why did my machine give such a different result then the sleep study?  The night I took my sleep study my machine counted .9 ahi and the sleep study came back at 6.
2:  does anyone think I need a titration?  My first study was also an in home study so I never went to a clinic.  Maybe I have another disorder besides sleep apnea.  My ahi was only 8 On my initial sleep study but I somehow developed right side failure.
3:  in sleepyhead I do not believe reras are counted.  Are these something I should worry about?  Are these not allowing me to get into rem sleep? 

I Appreciate the help in advance

[OpalRose]

Do I understand correctly that you used your Cpap along with and at the same time as the Watchpat device?

The Cpap would show as a "treated" result, whereas the Watchpat device should be worn alone and would show as "untreated" apnea.

[Kramer]

Yes, I had the CPAP device on.  Also, just something I forget to tell you is that I had severe o2 levels with my initial test.  They sent me to get my lung function tested and it came back all good.