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AHI usually higher in first hours of sleep, then decrease later - JUllian - 10-09-2020
I'll ask this generically here, but will provide detailed examples if a general answer is not feasible.
My average AHI is around 3. Looking at my OSCAR daily reports, the number of apneas/hypopneas is usually noticeably higher in the first 2 or 3 hours of sleep (AHI would probably be 4-8 or so , decreasing to almost none in the later 4-6 hours of sleep. Leaks don't differ in this way. Is there a common reason for this to happen? (If relevant: I do take 5mg melatonin half hour to an hour before going to bed, not good at avoiding TV/phone "blue light" sources before sleep, and do fall asleep pretty quickly.)
John
RE: AHI usually higher in first hours of sleep, then decrease later - Sleeprider - 10-09-2020
I think an Oscar chart would be very helpful. From your written description, you're using an Autoset with fixed pressure and unknown EPR settings. I think we can be a lot more effective if you give us the Oscar daily detail chart. Instructions for organizing and posting an attachment are in my signature links.
RE: AHI usually higher in first hours of sleep, then decrease later - JUllian - 10-09-2020
(10-09-2020, 09:40 AM)I\ll ask this generically here, but will provide detailed examples if a general answer is not feasible. Wrote: My average AHI is around 3. Looking at my OSCAR daily reports, the number of apneas/hypopneas is usually noticeably higher in the first 2 or 3 hours of sleep (AHI would probably be 4-8 or so , decreasing to almost none in the later 4-6 hours of sleep. Leaks don't differ in this way. Is there a common reason for this to happen? (If relevant: I do take 5mg melatonin half hour to an hour before going to bed, not good at avoiding TV/phone "blue light" sources before sleep, and do fall asleep pretty quickly.)
John
Sleeprider has recommended attaching OSCAR chart.
Last night's charts for the full night, the first half (before "bathroom break"), and second half:
[attachment=27257]
[attachment=27258]
[attachment=27259]
RE: AHI usually higher in first hours of sleep, then decrease later - Sleeprider - 10-09-2020
Now we can see that you are experiencing a great deal of upper airway restriction that is causing flow limitation, giving rise to a lot of hypopnea. With this information we can tell you will benefit from using EPR and a higher pressure, preferably in Autoset mode. My suggestion is to set your machine to Autoset mode. Use a minimum pressure to 7.0 and set maximum pressure at 10.0. Turn on the EPR full-time in the comfort settings and use a setting of 3. This will result in a starting pressure of 7.0/4.0 (inhale/exhale), and will increase if and as needed to 10.0/7.0.
The use of this bilevel pressure is effective in reducing both flow limitation and hypopnea. You did not have any obstructive apnea, so we know that an exhale pressure of 6.6 is probably adequate, and that is the basis of the maximum pressure. You're going to find this pressure change improves AHI and is much more comfortable as it will make your breathing easier. If you zoom into the flow rate on your chart, you will see a lot of flat-topped inspiration waves. This reflects the flow limitation (limited maximum flow rate) that results from an airway restriction most of the night. By having a higher inhale pressure than exhale pressure, the CPAP functions as a bilevel and gives you a push of air when you need it, helping you overcome that flow limitation and making it easier to breathe. The difference between inhale pressure (IPAP) and exhale pressure (EPAP) is call "Pressure Support" (PS) in bilevel therapy, and your Resmed Autoset is capable of providing up to 3-cm of pressure support as EPR.
RE: AHI usually higher in first hours of sleep, then decrease later - JUllian - 10-10-2020
Thanks much, Sleeprider, for the very clear instructions and explanations for improving my AHI and making my breathing easier. I will make the changes you recommend and let you know in a week or so how I'm doing.
I remain curious about the general question of the distribution of apneas/hypopneas during sleep. Do they tend to be distributed somewhat evenly through the night, or do they tend to be concentrated earlier (as mine have appeared to be) or later during sleep hours, or is no generalization possible (idiosyncratic, depending on the individual, or varying unpredictably even within the individual)?
John
RE: AHI usually higher in first hours of sleep, then decrease later - Sleeprider - 10-10-2020
Well we see everything here, and it seems CPAP therapy is a very individual thing. What we need to consider is, what is a hypopnea? It is a decrease in respiratory volume of 30% to 50% from what was recorded in the previous 90 seconds or so. As you first go to bed and settle in to sleep, you respiration slows and volume begins to reflect the lower level of activity and exertion. We sometimes see hypopnea flagged from that, but I suspect you have some variable respiratory volume, resulting from alternating flow limitation and recovery breathing, and we would need to look at a closer zoom to better understand that. During the times you have hypopnea, your flow limitation is high and we can see in the flow rate graph lots of spikes on both the inhale and exhale side. Try zooming in to where the respiration wave is clearly visible, about 2-3 minute segments, and take a screen shot. I'm sure you will see your respiratory volume varies, and that is the cause of the hypopnea being flagged.