Titration or Observed AHI Pressure?

CROWPAT · Post by **CROWPAT** » Sat Oct 20, 2007 8:22 am

I have had two titrations over the last six years. Both recommended 13 for pressure. I have used 11-13 for the last four months and see an anomaly on my software. AHI is generally below 1.0 when the machine is running at 11 (about 75-80% of the time). At 12 AHI goes up and at 13 it goes even higher. The sleep studies both showed centrals beyond 13 so I don't go there anymore. AHI averages around 4 night after night with some variation, but never down on 1 or less like I would prefer. Should I stay at 11-13 or move to CPAP mode at 11 and recognize that 11 is not enough to take care of all of the apneas? 90% pressure is around 11.5 or so.

Snoredog · Post by **Snoredog** » Sat Oct 20, 2007 8:57 am

I would just put it in CPAP mode at 11.

IF those events needing 12 or 13 cm pressure are central they can drive up the pressure from 11 if there is only 2 of them. IF there are 3 then they should be scoring as "NR" on the report.

So if you have any NR's on the report, then those are either "obstructive" events that pressure cannot eliminate or they are central which don't generally respond to pressure.

Sometimes the changing pressure of autopaps can cause those centrals, but I doubt very much the machine is the cause of them if they were seen on your diagnostic PSG.

Switch to CPAP mode and use 11, only switch back to auto mode should you suspect a pressure change is needed. Machine will still record sleep details in auto mode, you may have a few events that go unaddressed in that mode but I wouldn't worry about them.

ozij · Post by **ozij** » Sat Oct 20, 2007 1:39 pm

Suppose you sleep 10 hours a night, and suppose you spend 10% of the night at a pressure of 12. And supposes also that during the whole night, you had 4 apnea that needed a pressure of 12, all the rest were handled by lower pressures. 4 apneas in that 1 hour of 10% pressure translates into an AHI of 4. And if you had those 4 apneas is 4 15 minute sessions, that AHI is even more meaningless. And if you slept 8 hours, those 4 apneas occurring at 12 cms would calculate to an AHI of 6. And so on. And if it was 4 apneas, 5% of 8 of sleep needing 13 cms, your AHI for that pressure would be 12. The AHI (no. of apneas divided by time) increases when time decreases - for mathematical reasons.

There's is a reason the machine recommends a pressure based on where you spend 90% of your time. The AHI calculations for the residual times are artifacts - you can disregard them.

O.

RosemaryB · Post by **RosemaryB** » Sat Oct 20, 2007 6:37 pm

[quote="ozij"]Suppose you sleep 10 hours a night, and suppose you spend 10% of the night at a pressure of 12. And supposes also that during the whole night, you had 4 apnea that needed a pressure of 12, all the rest were handled by lower pressures. 4 apneas in that 1 hour of 10% pressure translates into an AHI of 4. And if you had those 4 apneas is 4 15 minute sessions, that AHI is even more meaningless. And if you slept 8 hours, those 4 apneas occurring at 12 cms would calculate to an AHI of 6. And so on. And if it was 4 apneas, 5% of 8 of sleep needing 13 cms, your AHI for that pressure would be 12. The AHI (no. of apneas divided by time) increases when time decreases - for mathematical reasons.

There's is a reason the machine recommends a pressure based on where you spend 90% of your time. The AHI calculations for the residual times are artifacts - you can disregard them.

O.

ozij · Post by **ozij** » Sun Oct 21, 2007 12:00 am

[quote="RosemaryB"][quote="ozij"]Suppose you sleep 10 hours a night, and suppose you spend 10% of the night at a pressure of 12. And supposes also that during the whole night, you had 4 apnea that needed a pressure of 12, all the rest were handled by lower pressures. 4 apneas in that 1 hour of 10% pressure translates into an AHI of 4. And if you had those 4 apneas is 4 15 minute sessions, that AHI is even more meaningless. And if you slept 8 hours, those 4 apneas occurring at 12 cms would calculate to an AHI of 6. And so on. And if it was 4 apneas, 5% of 8 of sleep needing 13 cms, your AHI for that pressure would be 12. The AHI (no. of apneas divided by time) increases when time decreases - for mathematical reasons.

There's is a reason the machine recommends a pressure based on where you spend 90% of your time. The AHI calculations for the residual times are artifacts - you can disregard them.

O.