Sierra

If you read page 33 of that Clinical Guide I gave you a link to above, it "explains it". However, it is a really confusing explanation. I think the only thing that is clear is that if you have no SD card, no detailed data is stored. I would get a card and look at the data yourself with OSCAR. OSCAR is the equivalent of what they call ResScan.

The AirSense 11 is a bit different but not much. The SD slot is still on the left side but at the top. This video shows how to insert it and where it is. https://www.youtube.com/watch?v=MFMUU7BAaTQ

The over the air stuff is just summary data, and does not have the detailed data that is recorded on the card. It works by connecting to your local cell phone network and probably uses 4G. That is why you have to take the comments based on it from your support vendor with a bit of a grain of salt. They do not see the detailed data. As I said it is more of a compliance monitoring tool. Looking at the data stored on the card is much more informative. They should be able to run software similar to OSCAR to look at the data, but they really can't unless you bring the card in for them to download the data from the card. And of course if there is no card in the machine the data is being lost instead of captured.

You can control your own machine by using the clinical menu. You can find out how by reading this AirSense 11 Clinical Guide. That said you should not change settings without a good understanding of how the settings impact the machine performance. OSCAR can help you a lot in this, but you still need to understand what each setting does.

You can post OSCAR Daily Report screenshots here for comments.

On the A10 ResMed the SD card is on the left hand side behind a flexible door you pry up. They typically come with a 4 GB SD card from the factory, but for some reason (possibly not honorable) some dealers remove the card. The card is the only place all the detailed data is stored. If it came with one, all the data should be still there for you to download with OSCAR. If not, you can put in a SD card from 4 GB up to 32 GB. No real advantage in more than 4 GB, so you may have one laying around from a camera or some other device where it is no longer needed.

The data that gets sent over the air by the machine is very limited summary data, and is mainly used for compliance purposes that some are obligated to provide.

Are you using OSCAR to track your results? It can be very helpful in determining what is happening during the sleep.

On a ResMed, make sure the EPR is set at 3 cm, and on a DreamStation the same with the Flex.

One of the best ways to make exhale easier is to increase the EPR (expiry pressure relief) to 3 cm. This reduces pressure on exhale only. Higher pressure on inhale is helpful to make breathing easier. On the DreamStation machines I believe this is called Flex. On the ResMed machines it is good to use the Auto for ramp time, and make sure the ramp start pressure is high enough.

It does take some time to get used to sleeping with a CPAP, and can be a bit annoying until you settle into it.

I am a bit pressed for time today but here is my quick response. Yes, higher than necessary pressure can cause CA events. In a nutshell what I have done is switch from Auto to fixed pressure CPAP mode. I then have experimented with lower and lower pressures trying to find a point where CA events are minimized without causing OA events to rise significantly. In my case that has turned out to be 11 cm. I have also set my EPR to 3 cm full time and that seems to minimize hypopnea events.

I forgot to answer your question about how the CPAP machine detects the difference between CA and OA events. When flow stops it starts to oscillate the speed of the fan. It then watches to see what happens to the pressure. If the pressure does not oscillate with the fan speed or does not oscillate significantly then it determines the airway is open and classes it as an CA event. It holds the pressure the same and does not increase it. And if the pressure does oscillate with the fan speed it determines the airway is obstructed, and then will increase pressure to try and clear it. If the flow stop for 10 seconds or more it gets recorded as an event. If less than 10 seconds it is not recorded. If you zoom in the scale with OSCAR you can see the machine doing this activity. If the machine cannot distinguish between CA and OA, usually when mask leakage is high, then it records it as an unidentified event. Hypopneas are flow restrictions without a complete loss of flow and are determined just based on flow.

You are correct in that the CPAP machine can report irregular breathing while you are still awake as apnea events. When going to sleep the ResMed machines minimize this effect by not counting any events until the ramp period is over. The newest machines when the ramp is set to Auto for time will detect when you go to sleep and end the ramp time. But, as you suspect when you are waking up this feature is not in effect and that period of time can increase the apnea count. About the only good way to get a handle on that is to use a freeware program called OSCAR which can read the data from the SD card on your machine and produce graphs of your whole night's sleep so you can see when apnea events occur.

Some call these false apnea events "Sleep Wake Junk", and disregard them. However, it is quite possible to have real central apnea (clear airway) events while obstructive events are low. Central and obstructive events are very different. Obstructive events are more common and can be reduced or eliminated by pressure from the CPAP to open the airway. Central events on the other hand occur with the airway open and more pressure is of no value. The better machines like the ResMed do not increase pressure in response to central apnea events. Central apnea events can be caused by many things, but the root element is the body deciding not to breathe. In most cases this is caused by a CO2 and Oxygen imbalance that is not stable. You have too much air, then too little, but the body has trouble bringing the balance under control. This is something you can see with OSCAR graphs.

If you download OSCAR you can post the graphs here for comments on what might be going on. You need a PC or Mac, and an SD card reader. I struggle with this issue and on average my CA events are about double the OA events. I have tweaked things with my CPAP and pretty much gotten it under control with my total AHI averaging currently at 0.82. But it takes time, and is not always successful. Here is a link to an article on potential causes. When you are on CPAP the first suspect is the CPAP itself. Using higher than require treatment pressure can cause CA events to go up.

https://www.mayoclinic.org/diseases-conditions/central-sleep-apnea/symptoms-causes/syc-20352109

These are the ones we got off Amazon. They are quite fine, but Amazon offers lots of choices, so there may be better ones. They collect dust faster than the coarse ResMed versions, and I replace them every 4 months. We were letting the ResMed ones go much longer than that, and that now appears to have been a mistake.

https://www.amazon.ca/gp/product/B07Z953DQG/ref=ppx_yo_dt_b_search_asin_image?ie=UTF8&psc=1

I see we bought them in November 2021, so we have been using them for a while now...

I think now, that the real secret to preventing this issue, may be to do a "big blow out purge" each time you replace the filter by turning the Mask Test feature on with the inlet filter out and the mask disconnected from the machine. that would ensure the highest possible air flow with no risk of blowing debris into the mask vent.