Session data

[dr.wise]

I'm using a Philips Respironics APAP. I noticed that the AHI is sometimes much lower when I get up in the middle of the night to use the bathroom than displayed in the morning, so I wanted to look at AHI by session. 

I exported session data (OSCAR_drwise_Sessions_2018-11-12_2021-02-27.csv) but don't understand some of the results.

First, session numbering doesn't start at 1 each night.

Second, the AHI column is all zeroes.

Am I misunderstanding the concept of sessions?

[Sleeprider]

Please follow the instructions in my signature links to Organize Your Oscar Chart, and post a screenshot image of the full night. We will be able to see the sessions and any issues. The chart is much better than a CSV table. Also see Attaching Files and Images.

[dr.wise]

       

Thanks very much. I'm including two screenshots to provide the basic graphs first and then the second to include the AHI values.

How is AHI calculated? It looks like it might be recomputed frequently, maybe every minute or two?

[staceyburke]

I know this is not what you asked, but I see a lot of positional apnea.  If you look at the rows H and O, you will see grouped events and that shows positional apnea. 

Positional apnea is when you get in a position during sleep where you cut off your own air way.  It can happen because you sleep on your back or to high of a pillow.  It is caused by chin tucking where the chin goes down to the sternum.  It can NOT be helped  with any pap machine, you have to get and stay out of the position that caused it,

If it is not as simple as side sleeping or changing a pillow you may need a collar.  Please look at the link at the bottom of this post.  It will have some charts showing people without collars and the same people with collars.  Many people have been helped with the use of a collar.

[dr.wise]

Thanks, Stacey. That's very plausible! I'll start by paying attention to staying on my side and keeping the pillow low.

[Sleeprider]

At a pressure of 5.5 to 20 your minimum pressure is clearly too low and the result is all the flow limitation, RERA, hypopnea and obstructive events.  I agree there is likely a positional aspect to the clusters of apnea.  When I look at your charts, we see clusters of apnea at 23:45, 02:30, and 04:20 which have sharp increases in inspiration time and spikes in minute vent.  That tells us you are expending more inspiratory effort to get the air you require. The spikes in minute vent are recovery breathing from periods where you are air-starved. It all adds up to many arousals that are sapping your sleep quality.   The Philips Dreamstation is very slow to increase pressure, and is reactive, rather than preventive, so I'm going to recommend higher minimum pressure.

You need a minimum pressure of about 9.0 cm to put you close to your 90th percentile of pressure.  By using that as a minimum you will prevent most obstructive events, and  your pressure will fluctuate less and be less disruptive to your sleep.  That is the starting place.  Once the problems from having pressure too low are gone, we can look at your charts and see if positional apnea is still an issue.  When we talk about "positional" we are not talking about sleeping on your back, but in sleep positions that cause the cervical spine to bend and obstruct your airway, simply chin-tucking.   I will link to the positional apnea and soft cervical collar wiki so you can read that.  I'm hopeful we will see significant improvement with the pressure adjustment.  You noted in your first post that your second session often has higher AHI, and this is likely because your are sleeping a bit deeper and not arousing to stop the positional events.

Positional Apnea http://www.apneaboard.com/wiki/index.php...onal_Apnea
Soft Cervical Collar http://www.apneaboard.com/wiki/index.php...cal_Collar

[pholynyk]

To get back to your original quest: "How is the AHI graph calculated?"

It is basically a running count of the number of 'events' in the previous 60 minutes. As such, I don't consider it particularly useful, since I can see the clusters in the Event Flags chart at the top, and also see which types of events are occurring.