Wide vs. Narrow Pressure Ranges (APAP)

Saw this thread that includes a discussion of pros/cons for default range of 4-20 cm H2O versus narrowing of settings to higher minimum and lower maximum pressures.

viewtopic/t184286/Switched-from-PR-Syst ... e&start=45

Was recently thinking about narrowing my settings from 8-15 cm since my leaks are worst at pressures higher than 13. Guess I'll start gradually knocking down the max pressure to see if I can keep AHI below 3. However, for the last six months, OSCAR data shows that 34% of the 99.5% pressures are >14 cm (99.5% pressure is very close to peak pressure). Even if I can't go below 15 cm, it's not the end of the world since dry mouth has been solved by using one Xylimelt per night (these things really work ).

While researching CPAP articles on PubMed, I came across one of the only controlled studies designed to study what happens to various clinical parameters with a wide pressure range (4-15 cm) compared to a narrower range (8-12 cm).

--> "Randomised short-term trial of high-span versus low-span APAP for treating sleep apnoea" https://pubmed.ncbi.nlm.nih.gov/26066701/

Patients had starting AHI of 39.4 and 33.5 cm, and had not used PAP therapy prior to study (ie, newbies). Here's what they found:

"After 3 months of therapy, we found no differences in residual AHI or ESS (Epworth Sleep Scale). However, the group HS (4-15 cm) proved less adherent than group LS (8-12 cm), respectively, with median 87 % (IQR, 60.5-97.5) versus 94 % (IQR, 80.0-98.3) of the nights using ≥4 h (P = 0.014) and mean (±SD) usage 5.7 ± 1.6 versus 6.4 ± 1.2 h/night (P = 0.049). The group HS reported more frequently nasal congestion, excessive oronasal dryness and nocturnal awakenings of at least moderate intensity, the latter with statistical significance (P = 0.005)." There were no significant differences in leak rate frequency between groups (latter my summary).

Your mileage may vary.

ElusiveSleep wrote: ↑

Fri Jul 15, 2022 2:14 pm

Saw this thread that includes a discussion of pros/cons for default range of 4-20 cm H2O versus narrowing of settings to higher minimum and lower maximum pressures.

viewtopic/t184286/Switched-from-PR-Syst ... e&start=45

That is not a good source of information.

The important thing is not this "range" it's the MINIMUM PRESSSURE that matters.

For most people. the max pressure, as long as it's high enough for your possible needs DOES NOT MATTER.

I agree with Palerider, because with an unrealistically low starting pressure, (4 or 5)
the machine cannot possibly react quickly enough to prevent most apneas.
Many pappers need at least an 8 to give the machine a good starting point.

ElusiveSleep wrote: ↑

Fri Jul 15, 2022 2:14 pm

Was recently thinking about narrowing my settings from 8-15 cm since my leaks are worst at pressures higher than 13.

Are the leaks disrupting your sleep?

ElusiveSleep wrote: ↑

Fri Jul 15, 2022 2:14 pm

However, for the last six months, OSCAR data shows that 34% of the 99.5% pressures are >14 cm

Not sure how you measured that, but if you mean "on 34% of the nights" the you're saying "my pressure is at or above 14 for only 0.5% of the night, and that only on 34% of the nights.
What is your median (50%) pressure? Is it higher or lower than 13?

palerider wrote: ↑

Fri Jul 15, 2022 7:15 pm

The important thing is not this "range" it's the MINIMUM PRESSSURE that matters.

Agree. Especially given the statistics that show what a small percentage of your time you do spend above 14.

Which brings us back to the unreported info: What percentage of your time are spending in large leaks? And do leaks that are not large leaks disrupt your sleep, or cause such things as dry eyes?

chunkyfrog wrote: ↑

Fri Jul 15, 2022 9:41 pm

the machine cannot possibly react quickly enough to prevent most apneas.

I’ve heard this claim before. Is there any studies that support the idea that “machines” are slow to react?

dataq1 wrote: ↑

Sat Jul 16, 2022 4:27 pm

chunkyfrog wrote: ↑

Fri Jul 15, 2022 9:41 pm

the machine cannot possibly react quickly enough to prevent most apneas.

I’ve heard this claim before. Is there any studies that support the idea that “machines” are slow to react?

The APAP computer is programmed to adjust the fan speed alternately with sensing
response. This means time is needed for the sensor message to reach the CPU,
and then the fan to speed up, as needed-the more steps, the slower it will reach
treatment levels.
How else would it be able to reach and maintain an effective pressure?
Don't you understand how these things work at all?

chunkyfrog wrote: ↑

Sat Jul 16, 2022 6:55 pm

Don't you understand how these things work at all?

Is there any studies that support the idea that “machines” are slow to react?

BTW, react to what?

dataq1 wrote: ↑

Sat Jul 16, 2022 9:42 pm

chunkyfrog wrote: ↑

Sat Jul 16, 2022 6:55 pm

Don't you understand how these things work at all?

Is there any studies that support the idea that “machines” are slow to react?

BTW, react to what?

Purposefully pretending to not understand something is a logical fallacy. Your posts are consistently filled with misinformation, aggression and fallacies. I have zero patience for this type of behavior. If I wanted to deal with this crap I would go visit the political discussion pages. Congrats you earned my foe list. Thats two in a week which is more than I've ever used it before. Are people getting more whiney and stupid or have a I just lost my patience. Hmmm. Something to ponder.

Anyone wondering about wide vs narrow ranges and just how important the minimum pressure really is...
there's a really good example here in this thread. Prime example of how the machine taking its own sweet time to get up to therapeutic pressures can lead to a lot of crap happening.
viewtopic/t184719/Adjusting-Settings-on ... se-10.html

babydinosnoreless wrote: ↑

Sun Jul 17, 2022 10:38 am

dataq1 wrote: ↑

Sat Jul 16, 2022 9:42 pm

Is there any studies that support the idea that “machines” are slow to react?

BTW, react to what?

Purposefully pretending to not understand something is a logical fallacy. Your posts are consistently filled with misinformation, aggression and fallacies. I have zero patience for this type of behavior. If I wanted to deal with this crap I would go visit the political discussion pages. Congrats you earned my foe list. Thats two in a week which is more than I've ever used it before. Are people getting more whiney and stupid or have a I just lost my patience. Hmmm. Something to ponder.

This is just one of dataq1's attempts to take away credibility when he sees something he doesn't agree with.

He's not even asking the right question. He obviously hasn't thought deeply about their behaviour and applied any critical thinking for himself.

Technically, CPAP machines are quite capable of moving up pressure very quickly, but they don't. We know this from simple observation, when one turns on a machine, it will move from 0 cm to ones starting pressure almost immediately, within a second. But, observing a session, one will never see a significant jump in pressure in a second or two, but a much longer period, 30 seconds to multiple minutes.

It does this so sensitive patients don't feel an abrupt pressure change, and because there is no way of knowing what to change the pressure to. We also know that the rate of pressure change is a part of the algorithm and not simply the machines ability to change rapidly because with ResMed (AirSense), it's a configuration item (Response Soft or Standard).

We see it *all* the time. People post their charts, we see the pressure increasing, and events occuring.

Prior to moving to AirCurve I did my own comparisons between Soft and Standard.

Standard outperformed Soft, for me:

Days . . . AHI . . . . Pressure . . . . . . . . . . . . . Mode
113 . . . 0.36 . . . . Min 11.2 Max 20.0 . . . . . Standard
16 . . . . 0.51 . . . . Min 11.2 Max 15.0 . . . . . Soft
82 . . . . 0.38 . . . . Min 11.0 Max 13.4 . . . . . Standard
24 . . . . 0.46 . . . . Min 11.0 Max 13.0 . . . . . Soft

Disregard the Max differences, my machine was never hitting the Max pressure and I was doing the adjustment to create a new entry in the OSCAR statistics page. But as you can see Soft response clearly doesn't perform as well as Standard, and the difference is the rate of pressure increase.

Dog Slobber wrote: ↑

Sun Jul 17, 2022 12:10 pm

Technically, CPAP machines are quite capable of moving up pressure very quickly, but they don't.

Thank you for your comment.
This OSCAR snip is a fair example of the my machine's responsiveness. Within 3 seconds the pressure is being increased upon the observation of a non-zero flow limitation assessment.
I would grant that folks here might argue that the magnitude of pressure change maybe lacking, but it doesn't look like the machine is lacking in response time.

BTW, in this example there are no OAs, Hs, occurring for 60 minutes prior to the snip, there are no leaks, and no snores. The only thing that is detected are flow limits at 05:09:52. The measured pressure begins to increase at 05:09:55.

dataq1 wrote: ↑

Sun Jul 17, 2022 2:37 pm

Dog Slobber wrote: ↑

Sun Jul 17, 2022 12:10 pm

Technically, CPAP machines are quite capable of moving up pressure very quickly, but they don't.

Thank you for your comment.
This OSCAR snip is a fair example of the my machine's responsiveness. Within 3 seconds the pressure is being increased upon the observation of a non-zero flow limitation assessment.
I would grant that folks here might argue that the magnitude of pressure change maybe lacking, but it doesn't look like the machine is lacking in response time.

BTW, in this example there are no OAs, Hs, occurring for 60 minutes prior to the snip, there are no leaks, and no snores. The only thing that is detected are flow limits at 05:09:52. The measured pressure begins to increase at 05:09:55.

No the measured pressure begins to increase at 05:09:46
And you *not* stating the position response-time position accurately.

The position is; if the pressure is set too low, then the machine may not have the time to get to where it needs to be and prevent events.

Picture this:
in the graph you presented the machine needed to get to about 13.5cm(epap) to address those flow limitations. It was at about 12cm and took about 32 seconds to get there. Now, what would have happened had the machine been at 10cm instead of 12cm? Assuming a similar increase rate it may not have gotten to 13.5cm soon enough to address the Flow Limitations and they may have developed into Hypopeas or OAs.

What if your minimum pressure was at 8cm? 6cm? 4cm?


When ones minimum pressure is too low, not getting there in time occasionally happens. How often it happens is dependant on how far away from one's optimum minimum pressure the machine happens to be at.

Dog Slobber wrote: ↑

Sun Jul 17, 2022 8:21 pm

For example, in the seconds preceding the *very visible* pressure increase, there could have been FLs measured at 0.2, or 0.1 or 0.05. Large enough to trigger a pressure increase, but not large enough to be represented on a trace at that level of granularity.

Thank you, since it's my OSCAR graph, I can increase the resolution of the seconds prior to the observed 0.24 FL. (I did say that that FL at 05:09:52 was the first non-zero FL). So here is the graph. The cursor readings all along the prior 60 seconds were all zeros. I could be persuaded that the pressure began to increase at 05:09:46, some 6 seconds in advance of any reported change in FL. However that would conflict with the steady-state of the FL measurements. (unless of course the pressure-time graph is out of sync with the FL-time graph)

dataq1 wrote: ↑

Sun Jul 17, 2022 2:37 pm

The measured pressure begins to increase at 05:09:55.

Dog Slobber wrote: ↑

Sun Jul 17, 2022 3:39 pm

No the measured pressure begins to increase at 05:09:46

dataq1 wrote: ↑

Sun Jul 17, 2022 9:35 pm

I could be persuaded that the pressure began to increase at 05:09:46, some 6 seconds in advance of any reported change in FL. However that would conflict with the steady-state of the FL measurements.

Just saw the latest posts, and there seems to be some subtle suggestion about my assertion that the the time prior to the FL increase was clean of other events. So here is the period prior to the FL at 05:09:52