dsm wrote:... Have you *ever* seen SV pressure support for you go higher than 20 CMs ? (allowing the epap is say 10 CMs) - if yes then you would have a real dose of *severe* cental apnea. I think JohnBFisher has said his can (23) - that is *very* high & reflects a serious effort by the machine to 'inflate' the user. ...
Yes, DSM, I can confirm that my machine will swing my pressure from EEP (equivalents to EPAP on Respironics) to EEP + almost PSmax. (I regularly see between 20 and 23cm H2O as the top number). So, as I fall asleep, I just stop trying to breathe. It takes over. Though it still can awaken me, I
*REALLY* do not mind the effort the ASV machine makes to compensate for my failure of my central nervous system to trigger nomral breathing.
On the downside of this high pressure swing, my mask can leak like a sieve. And there is no doubt there is a correlation between the leak rate and how I feel the next day. Good or better and I can function the next day. Poor or worse and I'm a basket case. Good or worse and I wake up with a headache. (I should really check my O2 saturation and heart rate during the night).
Why do I think these strong swings indicate a failure of my central nervous system? When I look at the data from my ASV unit, I see that I have those wild swings for a long time (60 to 90 minutes), then it suddenly settles down into a very small swing range (EEP to EEP+PSmin). That lasts for about 30 to 60 minutes. Then it heads back to the strong swings. And back to the low swings. And repeats until I awaken.
That almost certainly is following my sleep stages. It also indicates that I am probably not breathing well at all during Stage 1 and Stage 2. But I seem to suddenly transition to good breathing pattern. I assume (based on the duration) this is during deep sleep and REM sleep. Of course, without a full sleep study, I don't know for certain. This is just a guess based on the reading I've done over the past 20 years. But add to this that I have a known neurological condition that can impact the brain stem, and I would be willing to put some money on this horse.
Add to this that my pulmonary function tests indicate I have problems due to my obesity, which diminishes the volume I can breathe. I don't rule out Obesity Hypoventilation Symdrome (OHS). Decreased volume does NOT help. I understand that complicates my case. However, that normally only causes increased central apneas during deep sleep (Stage 3 of Non-REM sleep) and REM sleep. Central nervous system issues cause an increase in central apneas during Stage 1 and Stage 2 of Non-REM sleep. That seems to be what is occurring.
Plus the ABG test seems to show that hypoventilation occurs even during the daytime and it occurs due to lack of drive. There's lots of data in the ABG test that I don't understand as thurough as I would like. But it definitely indicates it is not just "anxiety" on my part. It's an issue while I am awake. And in this instance, those readings occurred 30 minutes after walking a couple of miles.
So, this is just one example of why I recommend people with problems with their therapy use a fully data capable machine. The information you can SEE with the graphs is amazing and very helpful.
Short answer: Unfortunately, yes a swing from EEP to EEP + PSmax is possible. It's not common. But it does happen.