Low respiration rate triggers central apnea clusters

[Grandpapa-G]

I have been lurking and learning for more than 10 months now and have achieved a lot by reading the posts. My experience appears somewhat different than most. I have not been well-served with a cpap machine jn “auto” mode. My sleep is broken by one or periods (1-2 hour duration each) that are dominated by clusters of what is identified as central (clear air) apneas. The vast majority of these events last 10-12 seconds and only a few are longer than 15 seconds. Resmed claims something like 85% success in distinguishing Obstructive from centrals – but even this small error rate drives my pressure up to max when auto mode is employed. By carefully logging when these clusters appear I have concluded that I am probably awake or at least switching in and out of wakefulness. I have also noticed that during these periods my average respiration rate drops from 12/sec to 8/sec and the tidal volume increases proportionately. I should note that I have been told by my doctor that I have a larger than average lung capacity. It is really not surprising that, during these periods of lower respiration rates a number of 10-second-events would be present – but are these apneas? These periods are often (perhaps always) accompanied by lucid dreaming.
I have benefited significantly from the beginning of my use of CPAP therapy. At my present fixed pressure of 7.4 in H2O my typical apnea rates are 0.0 to 0.3 for obstructive and 4-10 for central. Oddly enough on rare occasions when I consume three or more glasses of wine over an evening these numbers drop to as low as 0.0/0.0 respectively.
In my initial in-hospital overnight sleep test (12 months ago) I was diagnosed with moderate (45 AHI) apnea and 6 months later, on a bipap in-hospital overnight test I had no obstructive or centrals. Some periods of low respiration rate were noted but no low O2 saturation levels were reported.

[Rcgop]

This sounds like me. Are you saying switching from auto to fixed (with the correct pressure) solved the problem. I am about to give up with what I am trying with the auto mode and try the fixed method.

I will go back and check my respiration rate and push my Dr for a tritation study. Never had one, just a home test.

[Grandpapa-G]

Rcgop,
I tried to do a home titration by carefully scanning my daily data and estimate what pressure would be appropriate if I disregarded the clusters. I came up with 8.5-9.0 and initially set the fixed pressure to 9. I dropped it slowly to 7.4 over the objection of the vendor - but she accepted the results (increased comfort and lower leak rate). The second sleep test was supposed to be a titration but it was a disaster (that's another story) except that it confirmed I was drifting in and out of sleep during the centrals.

[Sleeprider]

GG, I'm just curious what your average or median tidal volume is. Mine tends to stay in the 670 to 730 range and minute vent in the 9.8-10.8 territory, which is way above what I have seen as average here. Resp rate average is around 15. I used to have more centrals, but AHI has settled out to be around 0.5 over the past few months.

I think CA clusters are pretty common during sleep/wake periods, and we even refer to it as sleep-wake junk since it is pretty meaningless to therapy stats.

[Grandpapa-G]

GG, I'm just curious what your average or median tidal volume is. Mine tends to stay in the 670 to 730 range and minute vent in the 9.8-10.8 territory, which is way above what I have seen as average here. Resp rate average is around 15. I used to have more centrals, but AHI has settled out to be around 0.5 over the past few months.

I think CA clusters are pretty common during sleep/wake periods, and we even refer to it as sleep-wake junk since it is pretty meaningless to therapy stats.

My median tidal volume is 440-460 (day to day variation), the minute vent is 5.80-6.1 during the same days. I have just checked days when the number are low (wine over dinner..) tidal volume is 420,500 and minute vent is 6.4,7.2

[Sleeprider]

Looks pretty normal to me. Welcome to the forum and since you are now over 4 posts, you can attach images if you think it will help. Sounds like your centrals are not much of a problem and may be just an artifact of the lower respiration rate. It's not hard to trigger a CA just shifting position, holding your breath, or taking a drink of water. I have also experienced the same lower AHI when I have enjoyed some wine. Maybe just deeper sleep?

[PaytonA]

9'
.........My sleep is broken by one or periods (1-2 hour duration each) that are dominated by clusters of what is identified as central (clear air) apneas. The vast majority of these events last 10-12 seconds and only a few are longer than 15 seconds. Resmed claims something like 85% success in distinguishing Obstructive from centrals – but even this small error rate drives my pressure up to max when auto mode is employed.

Are you thinking that central apneas are driving the pressure up?

9'
By carefully logging when these clusters appear I have concluded that I am probably awake or at least switching in and out of wakefulness.

This degree of wakefulness would probably cause sleep wake junk with clusters of central apneas.

9'
I have also noticed that during these periods my average respiration rate drops from 12/sec to 8/sec and the tidal volume increases proportionately. I should note that I have been told by my doctor that I have a larger than average lung capacity. It is really not surprising that, during these periods of lower respiration rates a number of 10-second-events would be present – but are these apneas?

An apnea is a cessation of breathing. The machines are very good at detecting the cessation of breathing especially for 10 seconds which is what is necessary to be called an apnea in this milieu. The machine can not tell if you are asleep or awake so it can easily call an awake apnea (which we are not really concerned with here so it should be ignored) a sleep apnea. The machine registers apneas. It is up to us to interpret if they are sleep apneas or not.

9'
These periods are often (perhaps always) accompanied by lucid dreaming.
I have benefited significantly from the beginning of my use of CPAP therapy. At my present fixed pressure of 7.4 in H2O my typical apnea rates are 0.0 to 0.3 for obstructive and 4-10 for central. Oddly enough on rare occasions when I consume three or more glasses of wine over an evening these numbers drop to as low as 0.0/0.0 respectively.

It sounds like your vino gets rid of the sleep/wake junk but that is just a wild a**ed guess on my part.

9'
In my initial in-hospital overnight sleep test (12 months ago) I was diagnosed with moderate (45 AHI) apnea and 6 months later, on a bipap in-hospital overnight test I had no obstructive or centrals. Some periods of low respiration rate were noted but no low O2 saturation levels were reported.

If CPAP works better for you than APAP that is fine. Use the CPAP. As long as your O2 saturation remains good, there is nothing to worry about if your respiration rate varies.

Best Regards,

PaytonA