Understanding min pressures

Yes, Pugsy, that's how mine look, meaning OA's with no flow limitations.

The majority of nights that I don't like look similar to that, meaning 10-20 minute clusters. The one in Sept. that was over an hour was more unusual. I would like to prevent clusters, period. Raising my max to 20 has helped for the times that the machine does respond.

AMK wrote:Yeah, I worded my question badly, though the answers still help. I'll try again. Pressure 8-20. Post-ramp, the min pressure the whole night never goes below 9.6. It is 9.6 immediately prior to a one-hour apnea fest. Would raising the min pressure to, say, 9, still help, even though as I said the min pressure never went below 9.6 the whole night? If I understand jnk and Ted correctly, the answer is, "Yes."

No, if it's 9.6 before the problem, it wouldn't matter if your min was 9, or 4. now, if your min was 9.8 or 10... then it would help.

palerider wrote:

AMK wrote:Yeah, I worded my question badly, though the answers still help. I'll try again. Pressure 8-20. Post-ramp, the min pressure the whole night never goes below 9.6. It is 9.6 immediately prior to a one-hour apnea fest. Would raising the min pressure to, say, 9, still help, even though as I said the min pressure never went below 9.6 the whole night? If I understand jnk and Ted correctly, the answer is, "Yes."

No, if it's 9.6 before the problem, it wouldn't matter if your min was 9, or 4. now, if your min was 9.8 or 10... then it would help.

That's what I would think, but it seems like once I raised my min to 8 I saw improvement even though the pressure after ramp never makes it down to 8.

AMK wrote:

palerider wrote:

AMK wrote:Yeah, I worded my question badly, though the answers still help. I'll try again. Pressure 8-20. Post-ramp, the min pressure the whole night never goes below 9.6. It is 9.6 immediately prior to a one-hour apnea fest. Would raising the min pressure to, say, 9, still help, even though as I said the min pressure never went below 9.6 the whole night? If I understand jnk and Ted correctly, the answer is, "Yes."

No, if it's 9.6 before the problem, it wouldn't matter if your min was 9, or 4. now, if your min was 9.8 or 10... then it would help.

That's what I would think, but it seems like once I raised my min to 8 I saw improvement even though the pressure after ramp never makes it down to 8.

The minimum setting is nothing more, or less, than the lowest the pressure will go to, and what your machine tries to get back down to when you're not having events. if you have events and the pressure spikes up, it doesn't matter if your minimum is 1, or 5 below where that happens.

To minimize events, you want the minimum a little above where most of them happen.

Refresh my memory but did we try to keep the minimum on the low side because you had some unpleasant side effects at higher minimum?
I can't remember if that was why we went lower or not.

TedVPAP wrote:

AMK wrote:Yeah, I worded my question badly, though the answers still help. I'll try again. Pressure 8-20. Post-ramp, the min pressure the whole night never goes below 9.6. It is 9.6 immediately prior to a one-hour apnea fest. Would raising the min pressure to, say, 9, still help, even though as I said the min pressure never went below 9.6 the whole night? If I understand jnk and Ted correctly, the answer is, "Yes."

Post a sleepyhead chart and we can use the data to give you a better assessment.

AMK,
Many people have tried to explain to you that properly setting the minimum pressure is strongly related to the maximum pressure you will need (which is different from the maximum setting). Do you understand?
As I said, if you post your sleepyhead data then we could use your data to help explain why you need to increase your minimum pressure setting. Words with data is much more compelling then just words.

TedVPAP wrote: . . minimum pressure is strongly related to the maximum pressure you will need . . .

I disagree. Minimum pressure may be set at or near the pressure that will be needed for much of the night, but for most users, that generally has nothing whatsoever to do with the highest pressures that may be reached occasionally. That's what the autotitrating algorithm is for.

There are often reasons to have the minimum set well below the maximum needed. Sure, you can run an auto in CPAP mode, if you choose to do so. But if you run it in auto mode, your highest-needed pressure does not dictate your min.

jnk... wrote:

TedVPAP wrote: . . minimum pressure is strongly related to the maximum pressure you will need . . .

I disagree. Minimum pressure may be set at or near the pressure that will be needed for much of the night, but for most users, that generally has nothing whatsoever to do with the highest pressures that may be reached occasionally. That's what the autotitrating algorithm is for.

There are often reasons to have the minimum set well below the maximum needed. Sure, you can run an auto in CPAP mode, if you choose to do so. But if you run it in auto mode, your highest-needed pressure does not dictate your min.

If the minimum pressure setting did not matter, then you could leave it at 4 cmH2O (or 6 if that is more comfortable). Obvious from reading this forum, most people need to elevate their minimum. The auto algorithm is not perfect so you must help it by keeping the pressure close to where the need is. How close will depend on the person.
I did not say to set the minimum to the highest pressure, I said a properly set minimum pressure is strongly related to your highest pressure need. As opposed to basing it off the other end, your lowest pressure need, which is what the OP was asking about.

TedVPAP wrote: . . . keeping the pressure close to where the need is. . . .

I agree, if "need" is defined as the pressure needed for 90/95 percent of the night.

TedVPAP wrote: . . . a properly set minimum pressure is strongly related to your highest pressure need. . . .

I disagree. HIghest pressure may be a significant factor for min for a person who breathes in such a way that the algorithm is mostly useless for him or her. But otherwise, I advocate ignoring highest pressure and looking at what pressure is needed most of the night.

But then, my views aren't always standard around here. In this forum, where people come who are having trouble with therapy, raising the minimum is often mentioned as something to try for comfort and effectiveness. But that does not, in my opinion, prove that an auto set wide open 4-20cm is useless for the majority of users. I believe that plenty of people out there get handed an auto set wide open and do just fine and never have a reason to look for this forum for help with anything.

But hey, just me.

@Pugsy: Sorry for mucking up this thread by harping on a technicality. Probably not helping the OP much. I'll let it go.

jnk... wrote: But that does not, in my opinion, prove that an auto set wide open 4-20cm is useless for the majority of users. I believe that plenty of people out there get handed an auto set wide open and do just fine and never have a reason to look for this forum for help with anything.

I agree. If the polls are anywhere near accurate then 10 cm is probably a very common pressure that the bulk of the people on cpap will use or even less. More people use around 10 ish and less than over 10.
Minimum of 4 with max of 20 will allow the machine to get to 10 rather quickly and be sufficient for most people. They don't do the increases in the blink of an eye but they don't take half an hour to get there if needed either.
Those people are happy with their therapy and won't come looking for forums like this.

If it ain't broken there's no need to fix it.

We get the outliers here...both in terms of just curiosity about their therapy and the people who things aren't working so great.
My DME tells me that myself and one other guy are the only people on cpap from his place of business who give a rats ass about what the machine says or does. They don't want to have to worry about data or anything else. They just say "fix it" when there is a problem and expect the medical care team to "fix it" because that's what they get paid for.

TedVPAP wrote: AMK,
Many people have tried to explain to you that properly setting the minimum pressure is strongly related to the maximum pressure you will need (which is different from the maximum setting). Do you understand?
As I said, if you post your sleepyhead data then we could use your data to help explain why you need to increase your minimum pressure setting. Words with data is much more compelling then just words.

I had one specific question about how min pressures work in general. I do not see where in this thread I asked for recommendations regarding my own min pressure. If I had, I would have posted sleepyhead data. Palerider understood me.

Pugsy, no, I haven't had any trouble with min pressures though so far my min hasn't been any higher than 8.

Okay, no special reason for keeping the minimum pressure lower. That's fine.

In general...if I am understanding your original question...once the pressure goes up to where it might want to stay during the night there isn't any real reason to do anything with the minimum pressure as long as you are happy with the results you get at where it seems to want to level out at for the bulk of the night.
Example...let's use 4 cm for grins as a minimum...if your minimum was 4 cm and the machine rather quickly made it up to say 8 cm and never dropped back down to 4 ...it really doesn't matter if you set the minimum at 4 or at 8 cm (or even anything in between) because the machine is going to go there and stay there for the bulk of the night and only increase above it as needed.
Then it uses the 8cm as a new jumping off point for when it might want to go higher for whatever reason. The 8 cm would effectively become the new minimum because the machine never drops down below it.

Now if you are unhappy with the new jumping off point for whatever reason (like those random ugly clusters you sometimes have) then you would have to give the machine a new jumping off point and we already know that 8 cm (using the above example) doesn't get the job done and you would have to raise the minimum to something above that 8 cm if you wanted a higher jumping off point because we already know that the machine likes 8 cm for the bulk of the night.

jnk... wrote:

TedVPAP wrote: . . . keeping the pressure close to where the need is. . . .

I agree, if "need" is defined as the pressure needed for 90/95 percent of the night.

TedVPAP wrote: . . . a properly set minimum pressure is strongly related to your highest pressure need. . . .

I disagree. HIghest pressure may be a significant factor for min for a person who breathes in such a way that the algorithm is mostly useless for him or her. But otherwise, I advocate ignoring highest pressure and looking at what pressure is needed most of the night.

But then, my views aren't always standard around here. In this forum, where people come who are having trouble with therapy, raising the minimum is often mentioned as something to try for comfort and effectiveness. But that does not, in my opinion, prove that an auto set wide open 4-20cm is useless for the majority of users. I believe that plenty of people out there get handed an auto set wide open and do just fine and never have a reason to look for this forum for help with anything.

But hey, just me.

@Pugsy: Sorry for mucking up this thread by harping on a technicality. Probably not helping the OP much. I'll let it go.

We are in violent agreement. For some people, leaving the range wide open is fine. For others, a reasonable min needs to be prescribed. That value should be based on where the need is, not where the need isn't.

AMK wrote:

TedVPAP wrote: AMK,
Many people have tried to explain to you that properly setting the minimum pressure is strongly related to the maximum pressure you will need (which is different from the maximum setting). Do you understand?
As I said, if you post your sleepyhead data then we could use your data to help explain why you need to increase your minimum pressure setting. Words with data is much more compelling then just words.

I had one specific question about how min pressures work in general. I do not see where in this thread I asked for recommendations regarding my own min pressure. If I had, I would have posted sleepyhead data. Palerider understood me.

Pugsy, no, I haven't had any trouble with min pressures though so far my min hasn't been any higher than 8.

Sorry, didn't mean to offend you. It is difficult to separate the academic question from questions related to treatment since your thread discusses your treatment and clusters.
Regarding the academic question, without knowing the exact algorithm being used a correct answer can't be had. I suspect that the prescribed minimum is not just used solely to set the minimum, but it is also used as a target which would impact the machine's response. So my answer is still yes, the minimum pressure setting influences the pressure even when it is set below your generally observed lowest pressure.

I have seen situations where the maximum pressures reached were reduced when a more effective/optimal minimum pressure was used.
Not all the time of course but I have seen it happen.
One comes to my mind where the person was giving the initial 4 to 20 settings and the maximum went to 18 often and it was painfully obvious that the OSA wasn't effectively treated and more minimum was needed. Once we got the minimum up to around 8 cm the AHI dropped from over 10 to less than 2 and the maximum pressure reached never went over 12. Win- win with just a little tweaking of the minimum pressure because over 14 she was having horrible aerophagia issues that went away once the pressure never got up there.

A lot depends on the REM and supine factor and how critical those pressure needs might be. Not everyone will see a marked difference in pressure needs when supine or in REM..and others might see a big difference.
So using a 90/95% pressure number as the holy grail of settings isn't always a good thing nor will it always be a good number to base therapy settings on.
90/95% numbers are easily skewed by relatively short periods of time at the higher pressures for some people....not all people of course but enough people that I don't put all my pressure eggs in the 90/95% basket.
Mainly because I am one of those people with first hand experience with sometimes high 90/95% numbers and sometimes not.
If we went by my 90/95% numbers...it looks like my minimum should be around 14..and as everyone can see from the above reports...way overkill.
I do quite well with a minimum of 7 even with EPR at 3....can't get much lower than that and still be comfortable.
I would like to try 4 cm minimum but it simply isn't comfortable for me and if I am not comfortable I can't sleep...and sleep is more important to me than numbers and experiments.

I will say this....I am using a lot less minimum with the ResMed apap than I was using with Respironics apap...to get same level of effective therapy.
That alone is sweet...let's face it...7 cm is more comfortable than 10 cm...at least for me.