I wish I'd joined this board earlier. I've just found out about hypocapnia today. I'm waiting for a sleep study for my central apnea but I fear I may wait a long time here in Canada post Covid. I'd be grateful for any advice or links to information on Central Apnea, hypocapnia and how to set up my machine using Oscar reporting to minimize the impact.
Generally I do pretty well with my Airsense 10 Autoset with pressure set between 5 and 10. I get few OA, and get more CA. I have long spells where my AHI is 2 or less. Even then I find myself waking up with a slightly rising heart rate most nights (my resting heart rate is 56 and I wake with it around 65-70). And I'm never quite sure why I wake, except that after a few seconds awake my heart rate takes off like a train and can hit 120-140. Oddly sitting partly up and leaning on my left elbow seems to be the best position to get my heart rate under control. Typically I get it under control using breathing techniques around 100 BPM or less but on occasion as I say it takes off.
Periodically however, and always following a night when I've had tachycardia, I end up with a bizarre phenomena, where every 5 minutes or so, my O2 level drops below 90 to as low as 85 (triggering an alarm at 88) even with my mask on. Around 92 I start to feel light headed and am woken up again. I use breathing techniques to get back to say 96, but as soon as I fall asleep again my O2 levels drop and I go through the cycle once again. Typically this sequence of events starts about 4 hours into sleep. I then go through the same exercise for several consecutive nights. I don't think I have a major issue with leakage, although I have nothing to compare with.
This morning, searching for information in frustration, I came across a study on Hindawi - Complex Sleep Apnea - published on 16 Feb 2014. In the study Complex Sleep Apnea is described and talks about the lack of CO2 in the blood stream leading to Central Apnea events, and that these events can happen at least 5 times an hour (in my case it's generally between 8 and 12).
The study refers to a period of suppressed respiration and when I check my Oscar reports I saw a period of low tidal volume that develops during sleep getting progressively lower over time. Say from 380ml to 180ml over three hours. The low point occurs just prior to me waking up.
It now appears that over the first three or four hours of sleep the level of CO2 in my blood stream diminishes to the point where I can have CA's of 20 to 30 seconds. But oddly enough, I don't always see a CA prior to waking. It's as though the level is so low my brain wakes me up. Then I end up with low O2 after handling the original tachycardia using breathing techniques, at which point it seems the low CO2 kicks in, and for the next few hours I have CA events continuously.
According to the article the latest technology ASV's etc minimize pressure to prevent 90% of OA but no more, judging that excess pressure is a risk for CA.
Is there any advice on how to set up an autoset machine for the best maximum pressure? Or links to information on the topic of Complex Sleep Apnea. Or suggestions or information about how to increase the level of CO2 in the bloodstream (though obvioulsy within reason!).
Thanks