Conflicting results from PSG and Dreammapper

[csl1]

Hello all. I had results from overnight PSG and MSLT tests today. There is a huge inconsistency with my Dreamstation data (ave AHI between 1 and 3, 90% pressure around 9) and the PSG results which showed around 18 hypopneas per hour and SpO2 averaging below 90%. It was the clinic PAP machine but it felt like a typical night to me. 

My sleep consultant says this happens sometimes and that the machine is not picking up the hypopneas and adjusting pressure. He has told me to fix pressure at 15 to see if this reduces desats. I know I will struggle with leaks at 15 but will give it a go. 

Was wondering if anyone else has heard of this?

[jwest]

PAP machine readouts are notoriously uninformative. The PSG is leagues more sensitive and should be our reference point.

If you share your OSCAR data here, we can examine it more closely and hopefully provide you with some more actionable advice. Is your doctor telling you to increase pressure because of the PSG O2 or is he seeing O2 desats from somewhere else? I'm a bit confused.

[Gideon]

Hypopneas are a reduction in your breath from normal. The issue is what is "normal".
A typical pap machine defines normal as a moving average and looks for a xx% reduction from this moving average. This does a very good job of determining a change based on the moving average. But what happens when the reduction is a long one with long simpling being defined as longer than the period of the moving average? In this case the hypopnea state becomes the normal, but it is already reduced from normal and as such doesn't detect the fact that you are still in a state of hypopneas. This impacts the auto algorithms to the point they don't recognize the hypopnea and will not increase pressure because they do not see the event.

It is cases like this that shifting to fixed mode, or a higher min pressure can really make a difference. Most here prefer the auto mode so I'd set a higher min pressure.
A proper pressure is one that treats most of the OA events ( we are not looking for zero).

[csl1]

Thanks for that. I can see how that makes sense. 

I tried fixing pressure to 15 last night but I struggled with it so may set it back to auto with a 10 or 12 min (was previously min 4).

What should I look for on Oscar to see if my pressure adjustment has worked? The AHI is not showing the 'normal' hypopneas so where do I look for them?

[OpalRose]

Your machine is compatible with OSCAR. Post a couple days data and we'll be able to answer your questions.

There are links in my signature line to guide you.

[Gideon]

The OSCAR team is looking at adding a line to the flow rate chart. This is not for sure but would be targeted for a release beyond 1.5 as we are evaluating release candidates at this time.

Unfortunately it will be manually set by the user at what they consider to be the "normal".

This is done by manually evaluating the zoomed view of the flow rate. Your best bet is to post several 3-minute views of what you think is your best breathing for evaluation here. The members here will help you.

[csl1]

That's great thanks.  Will sort some data uploads

[csl1]

Have attached 3 days including last night where pressure was fixed at 15.

Thanks

[jwest]

hey csl1

you should consider your leak rate, events, flow rate, flow limit, snore, etc. Don't worry, I'll explain a bit further, and feel free to ask any burning questions you might have, but there is a lot of helpful and telling data within the OSCAR daily readouts.

First off, your night at 15cm looks wayyyyyy better than the other two APAP nights. How is it better? Your AHI is lower, your snores are all gone (side note: remember snores can be a precursor to flow limitation / obstruction), your flow rate looks way cleaner (less volatility, straight edge, indicating consistent breathing), flow limitation was completely eliminated (~1.3 to 0).

Now, this doesn't mean you need 15cm. Your 95% pressure for the two APAP nights is about 10-11cm, so you can one of a few things: Bring your APAP min pressure up to, say, 9cm, or bring your set pressure down to whatever you feel like experimenting. For example, if the high pressure was really uncomfortable, then bring it down a bit more. If it was tolerable, bring it down by, say, 1cm to 14.

Also, as an aside, Gideon was suggesting you zoom in on the flow rate graph to about 3 minutes for the whole window, then share those photos so that we can see what your individual breaths look like.

[csl1]

Hi jwest

Wow it looks like it made a real difference.  I struggled with the fixed 15 so have switched back to APAP with an 11 minimum which was easier to handle.  Have attached the results for that and a zoomed in flow rate as suggested.

Thanks for all your help.  I was barred from driving on Monday as a result of the PSG results which was unexpected and will have a massive impact so it is good to know there may be some hope of improving things.