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Thoughts on setting minimum and maximum pressures
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robysue Offline
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Advisory Members

Posts: 1,228
Joined: Oct 2013

Machine: PR Dreamstation BiPAP Auto
Mask Type: Nasal pillows
Mask Make & Model: Swift FX
Humidifier: PR Dreamstation humidfier
CPAP Pressure: min EPAP = 4; max IPAP = 9;
CPAP Software: SleepyHead EncoreBasic EncorePro

Other Comments: Papping since September 2010

Sex: Female
Location: Buffalo, NY

Post: #31
RE: Thoughts on setting minimum and maximum pressures
(02-20-2014 02:08 PM)tahoemark Wrote:  robysue, I've read many of your posts and always find them thoughtful. I am concerned about my leaks, however it appears to be mostly short term events. Let me give you some data from last night, which was not a great night but fairly typical. According to sleephead my average leak was 7.43 and 95% was 37.2. Looking at the graph I see about a dozen instances where it spikes from 0 up to the 15-25 range most of these are a duration of under 15 seconds, however 3 of them were in the 2 minute range. More worrisome is that I had about 9 events going up to the 30-45 range these typically were in the 5 minute range.
So we've got a total of no more than 45 minutes of genuinely large leaks and maybe 6-10 minutes in leaks that may hit the Large leak territory. If the machine was running for about 7 hours, that's somewhere around 10-14% of the night (at most) in Large Leaks.

And none of the individual leaks are very long---the longest are about 5 minutes in length.

Unless a whole bunch of those 5 minute long large leaks are piled on top of each other with very little time between them, I'd not get too worried about this level of leaking.

In other words, I'd be more worried about the leaks if I was seeing one or two really long leaks (say both over 20-25 minutes) than a bunch of shorter ones.

Quote:I'm not sure what to make of this. As I said I don't think I'm mouth breathing, I am aware that I jar the mask from time to time and have to reset it. Any thoughts for how to monitor this? What to look for?
First, I wouldn't get very concerned about this pattern of leaks. I'd look at the leak line daily for a while. If the pattern of leaks doesn't change OR gets better, I'd not worry at all about trying to "fix" the leaks. If the longest of the large leaks starts to go from 5 minutes to say 25 minutes, I'd start to think about what I might need to do to fix the longest of the leaks.

Finally, I'd be more concerned about how the leaks coming from mask jars is affecting the continuity of my sleep: If the number of times you have to reset the mask starts to disrupt your sleep, you'll need to figure out a way of not jarring the mask quite so much. That may mean a different pillow or it may mean a slightly different sleeping position. Or it may simply resolve with a bit more time. If resetting the mask is not too disrupting to your sleep, I'd recommend not worrying about them or the leaks.
03-23-2014 10:57 PM
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robysue Offline
Wiki Editor
Advisory Members

Posts: 1,228
Joined: Oct 2013

Machine: PR Dreamstation BiPAP Auto
Mask Type: Nasal pillows
Mask Make & Model: Swift FX
Humidifier: PR Dreamstation humidfier
CPAP Pressure: min EPAP = 4; max IPAP = 9;
CPAP Software: SleepyHead EncoreBasic EncorePro

Other Comments: Papping since September 2010

Sex: Female
Location: Buffalo, NY

Post: #32
RE: Thoughts on setting minimum and maximum pressures
(03-23-2014 02:25 PM)yogigupta Wrote:  
(02-18-2014 01:30 PM)tahoemark Wrote:  I started at 4-20 on pressure...
I am NOT a physician. I also use ResMed S9 Autoset. I was precribed a CPAP machine set at 13.
To achieve that one has to do following:
Start Pressure = 4, it is automatic for the ResMed S9. You can not change it
Min Pressure = 13
Max Pressure =13
EPR Off
Ramp time = 5 minutes
You machine will start at 4 cm and reach 13 cm in 5 minutes.
With these settings, the S9 will deliver 13cm at all times (during the inhale and during the exhale) as soon as that 5 minute ramp is over.

And ramping from 4cm to 13 in 5 minutes is not going to be particularly comfortable for many people.

And by the way, if you go into the clinical menu you can increase that "Start Pressure" up as high as you want as long as the Start Pressure is strictly less than the Min Pressure. (If Start Pressure = Min Pressure, you've effectively turned the Ramp off.)

Quote:But thats really not the end of the story.
You should Turn on the EPR that makes breathing easier, reduce the Min Pressure by about 3. New setting will look like as follows
Starting Pressure = 4
Minimum Pressure = 10
Maximum pressure =13
EPR = On Full time.
EPR Level = 3.
You've actually done TWO significant changes to the setting here.

First you've changed the Min Pressure setting. With these settings the 5 minute ramp is going to go from 4cm to 10cm, not 13cm. This change in settings also changes the machine from running like a straight CPAP with EPR enabled to a real APAP. At the end of the ramp period, the set pressure will be 10cm and it will stay there until one or more of the following events starts to occur: Snoring, Flow limitations, and clusters of hypopneas and OAs. When these happen, the machine will start raising the pressure and it will keep raising the pressure until the events resolve or a pressure of 13cm is reached. Whenever the machine is happy with your breathing, it's going to start lowering the pressure down and it will keep lowering it until it reaches 10cm.

Second you've turned on EPR to its max setting of 3. What this means is that on every exhalation, the machine is going to lower the current pressure by 3 cm. (Although it will never lower the pressure below 4cm) When the pressure is at 10cm (on inhalation), the machine will lower the pressure to 7cm on exhalation. When the pressure is at 11cm (on inhalation) the machine will lower the pressure to 8cm on exhalation. And when the pressure is at 13cm (on inhalation) the machine will lower the pressure to 10cm on exhalation.

Quote:Now watch your AHI levels. Lowering EPR level will effectively increase the pressure..
For some people with a titrated pressure of 13cm, your strategy may lead to a possibly large increase in hypopneas and OAs. This is because of two things:

First, changing that min pressure from 13 to 10 reduces the pressure on both inhalation and exhalation for potentially long periods of the night, and for some people even a small decrease in the pressure setting from their titrated pressure can allow too many events through.

Second, the EPR reduction in pressure further reduces the exhalation pressure, and so when the inhalation pressure is already less than the titrated pressure, the exhalation pressure may be far enough below the pressure needs to allow additional OAs to occur.

That said: Many labs will often increase the pressure an extra cm or two during the titration test, usually very late in the night, just to see how well the patient tolerates the additional pressure. And many people can tolerate a bit lower pressure on exhalation than the titrated pressure because typically, the OAs are the first events to disappear during titration (they turn into hypopneas), and the tech continues to increase the pressure until the hypopneas disappear. And because of this many people do find that in practice EPR does not affect their overall AHI.

And if EPR allows you to sleep more comfortably and more soundly, then the AHI might indeed go down, particularly if CAs make up a sizable part of the AHI.
03-23-2014 11:24 PM
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