Flow Limitation

[BillMar]

I have been using CPAP for about 6 weeks which has made a huge improvement in my sleep. My AHI for the entire period is 4.01.

Yesterday when I saw the doctor I asked that the machine be set to APAP at a range of 8-16, instead of a fixed 8.0 to see if I could improve my AHI. he was reluctant to do so saying it might be difficult to adjust to, but ultimately agreed.

I did not sleep particularly well last night, and noticed this morning in the Sleepy Head stats, that there were 11 "flow limitation" events recorded. In the prior 6 weeks none were recorded. So I was surprised by the occurrence and the number.

What exactly are "flow limitation" events? Do they suggests some sort of machine failure, for example to cope with the higher pressure settings. (The max pressure was 12 or so from 6-7 AM. Most of the night the pressure was in the 8-9 range.) Or something biological...

Thanks

BillMar

[Nyre]

From what I read Flow limitations can be a precursor to OSA which will tell the machine to adjust its pressure accordingly to avoid an OSA event. Stuff noses can also cause flow limitations as well.

[retired_guy]

A simplistic way to look at it is a spike in flow limit indicates an apnea event that never had the chance to grow up and become a hypo, or oa.

The fact that you didn't sleep all that well is predictable. It takes a little time whenever you make any changes for your body to figure out the "new you."

What was your apnea events last night, (oa, ca, hypop) compared with previous nights? Not that you can tell anything conclusively based on one night, but might be interesting.

Lastly, I'm not sure I'd have gone from straight 8 to 8-16. I think I would have chosen 7 for the low, and not more than 12 for the max to begin with. But you're ok where you're at, it'll just take a little adjusting.

[BillMar]

A simplistic way to look at it is a spike in flow limit indicates an apnea event that never had the chance to grow up and become a hypo, or oa.

The fact that you didn't sleep all that well is predictable. It takes a little time whenever you make any changes for your body to figure out the "new you."

What was your apnea events last night, (oa, ca, hypop) compared with previous nights? Not that you can tell anything conclusively based on one night, but might be interesting.

Lastly, I'm not sure I'd have gone from straight 8 to 8-16. I think I would have chosen 7 for the low, and not more than 12 for the max to begin with. But you're ok where you're at, it'll just take a little adjusting.

Thanks for input. Helpful. The last 30 days I have been on CPAP the results are:

4.15 AHI composed of CA 2.22; OA .62; HA 1.31 and 0.0 Flow Limitation Index
With the new pressure settings (last night)
4.78 AHI composed of CA 3.53; OA .23 ; HA 1.02 and flow limitation index of 1.02 (11 events)

More than 50% of the AHI index over the time I have been on CPAP has been CA events.

[quiescence at last]

yes. as noted above, the flow limitations are biological. it means the air that you wanted to go thru a nasal passage or throat was slowed down based on a restriction in the flow path, whether it was congestion, relaxed muscles, the long-haired cat lying on your face, the pillow placed lightly over your nose and mouth by a partner that needs to muffle the noise.

QAL

[Sleepster]

there were 11 "flow limitation" events recorded. In the prior 6 weeks none were recorded. So I was surprised by the occurrence and the number.

I'm not sure, but perhaps flow limitations are recorded only when you're in auto mode. They are used by the machine to make adjustments to your pressure. Flow limitations can consist of reductions in air flow, or changes in the shape of the inspiratory (positive) portion of the flow rate graph. The claim is that they precede obstructions and therefore the pressure is raised in an attempt to prevent them.

How much time are you spending at pressures above 8?

[retired_guy]

Bill, I believe that as you get used to your new settings the CA's will calm down. So keep in touch and let us know what your results are for the next few days.

It was kind of interesting to see your OA and Hypop's dropped rather correspondingly to increase in flow limit events. Not surprising, and your numbers are really very good indeed. So good work, and know you'll get a good nights sleep tonight now that you're a "pro" with the auto settings.