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[CPAP] Can APAP open a blocked airway?
#1
If your airway closes while you are on APAP therapy, and the machine can raise the pressure significantly, will it reopen the airway? Or is CPAP preventive only, providing enough airflow to keep the tongue away from the soft palate most of the time but incapable of forcing the tongue away if an actual blockage occurs?

Let me put this another way. If an obstructive apnea event is recorded by the machine, it means that actual blockage has occurred, right? Prevention has failed. At this point, does an APAP machine with a sufficiently high maximum pressure reopen the airway, or must the patient do so on her own?

Just wondering . . .
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#2
They pulse the airflow a bit to determine if it's an obstructive or central event, and if they decide it's the former, they increase pressure. I don't think they reopen the airway, so much as encourage you to open it yourself without rousing you, then adjust to prevent recurrence. Now, that said, if there are no further events, they back the pressure down again.

Just from my observations.
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#3
Flow restrictions are often precursors to obstructive events. The machines respond to various levels of flow restrictions by increasing the pressure and thereby attempt to prevent obstructive events from being flagged. In that sense, they are proactive in preventing defined events from being flagged.

As for opening a closed airway after an obstructive event has occurred, it generally doesn't work that way with cpap. It's too late at that point and the response time much too slow but the pressure will be increased in anticipation of another event that may occur in the short term.

Dude
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#4
Short answer is no.

Once an obsrtuctive event has happened no cpap or apap machine has enough pressure to " force" the blocked airway open.

Once the event is over the machine will raise pressure a bit to prevent another from happening.
Hence the importance of having the min pressure high enough that it doesnt have to go very far to reach effective pressure
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#5
Aha. Figured as much. Thanks for your replies on this, gang.
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#6
(12-30-2015, 09:32 PM)Ghost1958 Wrote: Once an obstructive event has happened no cpap or apap machine has enough pressure to "force" the blocked airway open.

As mentioned by surferdude2, most commonly the pressure will start increasing even before any apneas or hypopneas occur, because the machine will sense Flow Limitation or snoring.

Except for uncommon CPAP machines which have a "backup" respiration rate, standard CPAP or APAP or bilevel or bilevel Auto machines do not attempt to react when breathing stops, to end apneas or hypopneas while they are still in progress. Instead, most self-adjusting algorithms wait for the apnea to end (by an arousal).

However, I think a CPAP machine with a backup rate such as an ASV (Adaptive Servo Ventilator) can overcome at least mild blockages. Having a backup rate means that if a breath is not started then the machine will automatically start cycling between IPAP (the pressure for inhalation) and EPAP (the pressure for exhalation) at the backup rate. This will happen regardless of whether the apnea is central or obstructive in type.

Yes, I think some obstructions *can* be too strong to be counteracted by a machine with a backup rate, especially if the machine is using "ST" therapy mode which uses manually-adjusted Pressure Support of 10 cm H2O or less. (Pressure Support is the boost in pressure to aid or cause inhalation.)

But I think some blockages can be overcome by an ASV (Adaptive Servo Ventilator) machine which automatically increases Pressure Support breath-to-breath, especially when the "Max Pressure Support" setting is very high, like in the range 10 to 15 cm H2O. That large increase in pressure will kick in to help or cause inhalation, regardless whether the apnea is central or obstructive.

In my Flow waveforms, which show the rate of airflow being inhaled and exhaled, I sometimes see the pressure cycling between 14 and 25 cm H2O while the Flow is flat lined at zero. These are strong obstructive apneas. And sometimes I see inhalation Flow during the high inhalation pressure but stop-and-go Flow during the lower exhalation pressure, because the air is having some trouble coming out at the lower exhalation pressure. I think this is when the machine is helping me to overcome weak obstructive apneas.


Quote: Once the event is over the machine will raise pressure a bit to prevent another from happening.

Right. For example, the standard ResMed AutoSet algorithm notes how long the apnea lasted and this is one of the things the algorithm takes into account when deciding how much to raise the pressure after an apnea.
Membership in the Advisory Member group should not be understood as in any way implying medical expertise or qualification for advising Sleep Apnea patients concerning their treatment. The Advisory Member group provides advice and suggestions to Apnea Board administrators and staff on matters concerning Apnea Board operation and administrative policies - not on matters concerning treatment for Sleep Apnea. I think it is now too late to change the name of the group but I think Voting Member group would perhaps have been a more descriptive name for the group.
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#7
(12-30-2015, 06:56 PM)Canmore Wrote: If your airway closes while you are on APAP therapy, and the machine can raise the pressure significantly, will it reopen the airway? Or is CPAP preventive only, providing enough airflow to keep the tongue away from the soft palate most of the time but incapable of forcing the tongue away if an actual blockage occurs?

Let me put this another way. If an obstructive apnea event is recorded by the machine, it means that actual blockage has occurred, right? Prevention has failed. At this point, does an APAP machine with a sufficiently high maximum pressure reopen the airway, or must the patient do so on her own?

Just wondering . . .

WOW - I had hadn't thought about how this works - thanks all for the discussions.
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#8
so I have a question please - I am to have two appointments next week which will result in buying my APAP machine. I have not trialled a set pressure machine - would this stop any apneas before they occur?
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#9
(01-04-2016, 03:42 AM)Diane1048 Wrote: so I have a question please - I am to have two appointments next week which will result in buying my APAP machine. I have not trialled a set pressure machine - would this stop any apneas before they occur?

Hi Diane1048, please see these machine recommendations from member Archangle:
http://www.apneaboard.com/wiki/index.php...ne_Choices

APAP (auto-adjusting CPAP) machines can also be operated in fixed-pressure "CPAP" therapy mode. Two machines in one.

It is pretty common for a fixed-pressure machine to be set to the 90 or 95 percentile pressure, which is the pressure an APAP machine would be at or lower approximately 90% or 95% of the time. Usually, this will not eliminate all apneas and hypopneas, but it will usually eliminate nearly all.

Some people using APAP machines prefer to set the Min Pressure setting as high as would be normally set on a fixed-pressure machine, and to set the Max Pressure setting somewhat higher, so most hypopneas and apneas and RERAs are avoided, but if higher than normal is occasionally needed the machine will automatically provide higher pressure.

But I think most people using APAP machines prefer to have the Min Pressure set about 3 to 5 lower than where a fixed-pressure setting would commonly be set, so the pressure is raised high only when needed.



Membership in the Advisory Member group should not be understood as in any way implying medical expertise or qualification for advising Sleep Apnea patients concerning their treatment. The Advisory Member group provides advice and suggestions to Apnea Board administrators and staff on matters concerning Apnea Board operation and administrative policies - not on matters concerning treatment for Sleep Apnea. I think it is now too late to change the name of the group but I think Voting Member group would perhaps have been a more descriptive name for the group.
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#10
Thanks vsheline

only a month or so into my CPAP treatment my pressure is set at 4 - 12 and I have not had a problem with this pressure so far so long as I relax into the 4 level and fall asleep.

So it will be interesting to see how I have been going and it is working consistently!
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