Why did my pulmonologist tell me to set my pressure to 13-15 if I have an Auto CPAP?

[mileena]

I have a Philips DreamStation Auto CPAP. My doctor knew that and read my SD card. He said to switch my pressure to 13-15 cmH2O. I had previously had it at 14-20 I think, and the original prescription from another doctor was for 4-20. My question is if I have an Auto CPAP, what do the pressure settings matter since isn't supposed to be automatic anyway?

[palerider]

I have a Philips DreamStation Auto CPAP. My doctor knew that and read my SD card. He said to switch my pressure to 13-15 cmH2O. I had previously had it at 14-20 I think, and the original prescription from another doctor was for 4-20. My question is if I have an Auto CPAP, what do the pressure settings matter since isn't supposed to be automatic anyway?

Because the machine isn't magic, it raises pressure because of breathing problems, then tries to lower it back to the minimum pressure set. This causes repeated problems until the minimum is high enough to prevent most issues.

4-20 is the factory defaults, your "another doctor" did nothing.

13-15 is probably almost as dumb, if you were getting good results at 14-20, reducing the max pressure in most cases does nothing good.

[Midwest_non_sleeper]

I have a Philips DreamStation Auto CPAP. My doctor knew that and read my SD card. He said to switch my pressure to 13-15 cmH2O. I had previously had it at 14-20 I think, and the original prescription from another doctor was for 4-20. My question is if I have an Auto CPAP, what do the pressure settings matter since isn't supposed to be automatic anyway?

....reducing the max pressure in most cases does nothing good.

...and can actually be harmful if it's set too low when the machine wants to go higher to correct a collapsing airway, but can't because it's set too low - resulting in a collapsed airway and an apnea event.

[raisedfist]

It would be hard to guess since we can't read your doctor's mind. But in general, just because APAP is automatic, doesn't mean that it can't be set for failure. Set it to 4 - 20 with a DreamStation, and you are double guaranteed a terrible night.

[D.H.]

A setting of 13 to 15 will never go below 13 and never go above 15 (excluding ramp time). It's a fairly narrow range, but it might be right for you.

In general, you should set the max lower than the machine max if you're experiencing clear air events or other distress or discomfort when the machine hits the higher pressures.

[mileena]

Thanks everyone for good answers. When I was on the road and using li-ion battery power, I tired not to go too high with the pressure, or my batteries would be more drained in the morning and take longer to charge, or even run out while I was sleeping. I found the colder the atmospheric temperature was, the less time the batteries lasted.

[Okie bipap]

I use a narrow setting on my machine. I am currently running 18 to 21. I was using 17 to 20, but I was still showing periods of snoring, so I raised my pressure range. There is nothing wrong with a narrow pressure range if it controls your sleep apnea. The only way to know is to try it for a few nights and see how you do. I could have left my upper limit at 20 since I very seldom ever went over 19.

[AmSleepnBetta]

I was using 17 to 20, but I was still showing periods of snoring, so I raised my pressure range....The only way to know is to try it for a few nights and see how you do. I could have left my upper limit at 20 since I very seldom ever went over 19.

MAIN POINT OF REPLY (I did not intend to hijack the thread, but have rambled on elaborating and done so. Please accept my apologies mileena and All.)
Thanks for that report, Okie, about snoring--not events--justifying more pressure. I've been slow to learn that is needed. I have chased the holy grail and found a lot of 0.0 AHI (0.1 the past 3 months--after starting over 3 years ago at neighborhood 60.0). But as you can see from yesterday's graphic workup it is not a picture of restful sleep. Thanks to you and everyone in this thread I'm going to raise that minimum APAP pressure 1 cm starting tonight and "for a few nights" to try to shave those always-present FR whiskers off (that is, to suppress snores and flow limitations). I hope my few and new episodes of palatal prolapse do not increase. (I don't understand the mouth exhalation thing in my PP because I wear what I believe is a very effective mouth seal; the blockage must still allow enough air to escape through the nose.)

I'm still trying to understand snores and flow limitations. My home brew actigraph at the top of the graphic raises that old question in my mind. Did the chicken or egg come first? The snore or the shift in position? It's murky, because as you can see (maybe everyone sees this in their SH graphs) there are large snores when first turning on the Autoset with the mask on and, again, when returning from a break, the latter at about 05:10 of the FR graph.

Looking at the right edge of the four grey vertical rulings (numbered 1-4, left to right):

1: This is a rarity among the FR spikes (on this and other nights) because the head shift to the right of about 15 degrees (red color) is not associated with a significant snore or FL. But the motion does have the usual accompanying "spikes" in TV and PR--even SpO2. I believe this is only a comfort seeking motion.


2: This more lasting motion scores a hit, a spike, on all but FL--even though small for PR.

3 and 4: Differ from "2" with larger spikes.

What is usual with these graphs is to see almost every motion accompanied by a significant snore (rarely only a FL). But, probably due to losses to filtering of accelerometer data , numbers of FR spikes are not accompanied by indications of motions.


When I look at my graphs it seems I can conclude that almost every sudden but small increase in either PR or TV will indicate some level of motion. TV increases are almost always coincident with motions and FR spikes--much moreso than PR increases.

Suggestions for the following madness would be appreciated: I've been thinking about ways to go beyond the green vertical bars that indicate only the relative accelerations in the upper graph (accelerations relative to g, that is, as in weight (lb) = mass (slugs) x g, where g=32 (ft/sec)/sec). Daydreaming here: Short of gathering and analying data from load cells under the bed's four legs, maybe--and maybe doing the same with accelerometers on each limb (or more), I can't see how to assess the amount of effort expended in different motions of different body parts. I'd like to see if simply looking at TV and PR spikes wouldn't be good enough for most of us to evaluate restless and snore caused motions. I have seen writeups where sleep activity/"work" was measured via oxygen use. Anyway, my 3-axis accelerometer has been great in showing me that I must not sleep inside an arc 30 degrees to either side of supine.

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