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max pressure all night
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A KLERK Offline
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Post: #1
max pressure all night
As member of the Dutch Apneuvereniging I receive by time and time stories about a RasMed S9 Autopap that runs to its maximum pressure within a few minutes and stays there all night. I.e. a set pressure range of 8 to 10 cmH2O results in 10 cmH2O all night.
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My reaction would be: the upper level is too low. AHI in one case is round 10.
Please help me clarify...

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07-23-2014 02:37 PM
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zonk Offline

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Post: #2
RE: max pressure all night
(07-23-2014 02:37 PM)A KLERK Wrote:  As member of the Dutch Apneuvereniging I receive by time and time stories about a RasMed S9 Autopap that runs to its maximum pressure within a few minutes and stays there all night. I.e. a set pressure range of 8 to 10 cmH2O results in 10 cmH2O all night.

My reaction would be: the upper level is too low. AHI in one case is round 10.
Please help me clarify...
I think so too. Beside too many hypopnea and apnea events being flagged, pressure staying at the maximum pressure for most of the night which is an indication the machine could use a bit more pressure. 8-10 is a narrow range, not much room between 8 and 10
Whats the leak and flow limitation graphs look like?

Whats the model of your S9 Auto (AutoSet or Escape Auto)?
The model shown in the chart is AutoSet Spirit, the AutoSet Spirit is an S8 (not an S9), maybe the S9 sold in Holland have different names
07-23-2014 04:07 PM
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retired_guy Offline

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Post: #3
RE: max pressure all night
Yes. If it is at the high pressure most of the time and you are still having obstructive apnea, then you should increase it a little at a time.

I would try 8 - 12 for a few days and see what happens.
07-23-2014 07:25 PM
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A KLERK Offline
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Post: #4
RE: max pressure all night
(07-23-2014 04:07 PM)zonk Wrote:  I think so too. Beside too many hypopnea and apnea events being flagged, pressure staying at the maximum pressure for most of the night which is an indication the machine could use a bit more pressure. 8-10 is a narrow range, not much room between 8 and 10
Whats the leak and flow limitation graphs look like?

Whats the model of your S9 Auto (AutoSet or Escape Auto)?
The model shown in the chart is AutoSet Spirit, the AutoSet Spirit is an S8 (not an S9), maybe the S9 sold in Holland have different names

It's a little confusing: I have an S9 AutoSet myself. The question however was about a member of our Board, who has an AutoSet too. But the graph was from another member who showed he had the same problem with an S8 Autoset. I'm waiting for the data from the original poster.
BTW. The leak in the provided graphs was very low, of course there is no data on Flow Limitation in the S8...

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07-24-2014 03:53 AM
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robysue Online
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Post: #5
RE: max pressure all night
Quote:But the graph was from another member who showed he had the same problem with an S8 Autoset.

Since the data comes from an S8 AutoSet, it's important to understand the following things about the S8 Auto algorithm:

1) If I recall correctly, the S8 AutoSet does NOT increase the pressure in response to Hs.

2) The S8 increases the pressure in response to apneas only if the pressure is less than 10cm. Any apnea scored when the pressure is AT or ABOVE 10 cm is assumed to have a higher probability of being a central apnea. And the machine is programmed to NOT increase the pressure in this case in order to NOT inadvertently increase the pressure too much and start triggering long chains of centrals in folks with a tendency of having pressure-induced centrals at high(er) pressures.

3) The S8 Auto will continue to increase the pressure when it is above 10cm in response to snoring. And while it may not record a Flow Limitation graph, the S8 may still be capable of analyzing the flow rate (which is NOT recorded to the card) and detecting and responding to flow limitations with an increase in pressure even when it is above 10cm.

In other words, if the min pressure is left at 8cm, increasing the max pressure may not do much to fix the problem of too many events sneaking through.

So the person in question may need to raise both the min and max pressures to eliminate these clusters of events. I'd suggest going slowly: Increase both pressures by about 0.5cm at a time and collect several days worth of data before the next pressure increase.

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See my Guide to SleepyHead
(This post was last modified: 07-24-2014 10:48 AM by robysue.)
07-24-2014 10:47 AM
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A KLERK Offline
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Location: Oosterhout, The Netherlands

Post: #6
RE: max pressure all night
RobySue, thank you for this explanation. I have all the documentation for S9 machines, but hardly for S8 automates.
However this is not a solution for the 'always max' questions. Do you agree with the two others above? Or maybe you see something else there?
For all of you: I'm waiting for data from members with the same complaints. You'll hear about it soon, I hope.

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07-24-2014 01:07 PM
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robysue Online
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Post: #7
RE: max pressure all night
A KLERK Wrote:However this is not a solution for the 'always max' questions. Do you agree with the two others above? Or maybe you see something else there?

If you're running at max pressures for most of the night, I think the answer to "Should I increase the max pressure setting?" is It depends.

If the problem is that there are too many obstructive events and you are still feeling bad, then increasing the max setting might help---if the machine is going to respond to the events by increasing the pressure. In the particular example, however, the S8 AutoSet is NOT going to increase the pressure in response to a cluster of OAs that happen when the pressure is already at 10cm. (If there is snoring present, the S8 will increase the pressure for the snoring, but not for the OAs.) In other words, if the person whose S8 data we're considering needs more pressure to control OAs and Hs, then the only way s/he is going to get it is to increase the minimum pressure setting.

If the problem is that the min pressure is way too low and too many events are getting through because the min pressure is too low, then increasing the min pressure may do more to fix the problem than increasing the max pressure.

If the problem is that there are way too many CAs being scored, increasing the max (or min) pressure may make things worse. And if the max pressure is 15cm or more and there are long strings of OAs in the middle of a periodic waxing/waning breathing pattern, it's important to consider the possibility that the "OAs" are actually misscored CAs and that you may be looking at a long chain of pressure induced centrals. In which case increasing the max pressure is likely to make things worse.

And finally, if the reason the pressure is maxing out is just flow limitations and the AHI is consistently below 5 AND you're feeling pretty good, the best thing may just be to leave things alone: In this case an increase in pressure may not make the FL much better and it may trigger problems that you don't currently have with leaks, aerophagia, or pressure induced centrals.

Questions about SleepyHead?
See my Guide to SleepyHead
(This post was last modified: 07-24-2014 01:50 PM by robysue.)
07-24-2014 01:46 PM
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zonk Offline

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Post: #8
RE: max pressure all night
(07-24-2014 01:07 PM)A KLERK Wrote:  RobySue, thank you for this explanation. I have all the documentation for S9 machines, but hardly for S8 automates.
However this is not a solution for the 'always max' questions. Do you agree with the two others above? Or maybe you see something else there?
For all of you: I'm waiting for data from members with the same complaints. You'll hear about it soon, I hope.
Answer: See "suggested titration protocol for CPAP"
http://www.sleepapnea.com/downloads/1002...fGuide.pdf

From S8 AutoSet provider manual, the manual is available via email from here http://www.apneaboard.com/adjust-cpap-pr...tup-manual
AutoSet mode
The treatment pressure required by your patient may vary through the night, and from night to night, due to changes in sleep state, body position, and airway resistance. In AutoSet mode S8 AutoSet II provides only that amount of pressure required to maintain upper airway patency
You can set the minimum and maximum allowable treatment pressures. The device analyzes the state of the patient’s upper airway on a breath by-breath basis, and delivers pressure within the allowed range according to the degree of obstruction

The AutoSet algorithm adjusts treatment pressure as a function of three parameters: inspiratory flow limitation, snore, and apnea
The flow sensor, located in the S8 AutoSet II device, enables detection of inspiratory flow limitation and apneas. The pressure sensor, also located in the device, enables measurement of pressure and snore.
Inspiratory flow limitation indicates silent partial obstruction. When your patient is breathing normally, the inspiratory flow measured by the device as a function of time shows a typically rounded curve for each breath.

The AutoSet algorithm analyzes the shape of the central part of the curve for each breath. If the inspiratory flow-time curve falls below a certain threshhold, the pressure is increased. Inspiratory flow limitation, or partial airway closure, usually precedes snoring and obstruction. Detection of this flow limitation enables the device to increase the pressure before obstruction occurs, making treatment pre-emptive. If no further flow limitation is detected, therapy is reduced towards the minimum pressure with a 20-minute time constant.

Flattening is a measure of silent inspiratory airflow limitation. Flow limitation with loud snoring is handled by the snore detector. When a patient snores, sound is generated and the inspiratory flow/time curve is distorted by the frequency of the sound.

The AutoSet algorithm assigns an arbitrary value between 0.0 and 2.0 to the average amplitude of the snoring detected for the past 5 breaths. A value of 1.0 is equivalent to approximately 75 dBA measured 10 cm from the nares.
Treatment pressure increases by up to 0.2 cm H2O per second (proportional to the severity of the snore) for snore above 0.2 snore units. When snore is less than 0.2 snore units, therapy is reduced towards the minimum pressure with a 20-minute time constant.

An apnea is defined as a greater than 75% decrease in ventilation. The AutoSet algorithm scores an apnea if the 2-second moving average ventilation drops below 25% of the recent time average (time constant 100 seconds) for at least 10 consecutive seconds. Treatment pressure increases based on the duration of the apnea. The pressure will not rise above 10 cm H2O when an apnea is detected, to prevent an inappropriate response to central apneas. Initial pressure increases are rapid, but the rate of increase diminishes as the pressure approaches 10 cm H2O. When no further apneas are detected, therapy is reduced towards the minimum pressure with a 20-minute time constant.

A hypopnea is defined as a 50 to 75% drop in ventilation. A hypopnea is scored if the 8-second moving average ventilation drops below 50%, but not below 25%, of the recent average for 10 consecutive seconds. In order to avoid falsely responding to central hypopneas, the AutoSet algorithm does not respond to hypopneas but rather to the associated snore or flow limitation
(This post was last modified: 07-24-2014 05:19 PM by zonk.)
07-24-2014 04:51 PM
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Lukie Offline

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Post: #9
RE: max pressure all night
I have an s9 autoset and it seems to be doing the job. I have been using it at a setting of 6-16 since December. At first I had a mixed bag of mostly hyponeas and centrals with an occasional obstructive. My AHI has always been below 2. A few nights ago I noticed I had a lot of obstructives....many more than usual with an AHI of 2. My pressure went up accordingly to the highest it has ever gone to 15.7. Well, things must have settled down because last night my AHI was 0.1 with one obstructive apnea for the whole seven hours of continuous sleep. The highest pressure reached was 12 with a median of around 8. I think I may be getting more obstructives now because I trust the machine and sleep much more deeply and have a lot more REM time than in the beginning. Also I may even occasionally sleep on my back...which I never did before.
07-24-2014 07:31 PM
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JimZZZ Offline

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Post: #10
RE: max pressure all night
(07-24-2014 07:31 PM)Lukie Wrote:  I think I may be getting more obstructives now because I trust the machine and sleep much more deeply and have a lot more REM time than in the beginning. Also I may even occasionally sleep on my back...which I never did before.
I too notice a slight increase in OAs on nights when I awaken to find I'm on my back. Like you, I believe that as my trust increases, I'm more likely to sleep deeply and on my back. Before PAP, I avoided my back to reduce snoring.
07-25-2014 05:58 AM
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