ResScan - why Hypopnea Det. Graph just a box?

Hi all,
When in ResScan > Deatailed Graphs > Events, why are "Hypopnea" events displayed as a simple box icon on the 0.00 line, while "Obstructive" and "Central" get an arrow icon up to the seconds of duration time with that number on top? Isn't it just as important to know how long an hypopnea event lasted?

I actually tried to find the answer to this in the ResScan Clinician's Manual, but could not find it there.

I have read that the apnea events only get scored if they last for 10 seconds or more, including hypopneas, so my ResMed S9 must be calculating the duration in order to determine to report it or not. Why then does ResScan not report the number of seconds in the Detailed Graph > Events panel?

My guess is that this is leftover from the old A10 algorithm.

If your read this: An interview with Dr. Michael Berthon-Jones the physician one of the inventors the ResMed auto's algorithm
You will see that originally, the people who invented the ResMes Autoset alrorithm did not consider hypopneas as indicators of obstruction:

Why doesn’t ResMed's AutoSet respond to
hypopnoea?When you are lying quietly awake, or when you
first go to sleep, or when you are dreaming, you
can have hypopneas (reductions in the depth of
breathing) which are nothing to do with the state of
the airway. For example if you sigh, which you do
every few minutes, you usually have a hypopnea
immediately afterwards. This can also happen if
you have just rolled over and are getting settled, or
if you are dreaming. And the annoying thing is that
when you are on CPAP, this tendency to have what
are called central hypopneas - hypopneas that are
nothing to do with the state of the airway - is
increased. If you make an automatic CPAP device
that responds to hypopneas, you will put the
pressure up to the maximum while the patient is
awake.
Do you think there is a misconception clinically
that all hypopneas should be treated ?For simple obstructive sleep apnea, central
hypopneas should not be treated. They are not a
disease. Everyone has them. And they don’t go
away with CPAP.

This non-response to hypopneas is still there in the Enhanced AutoSet Algorithm used in the S9.

ozij said, "This non-response to hypopneas is still there in the Enhanced AutoSet Algorithm used in the S9."

So then the S9 does not respond to an hypopnea event, and that's why it doesn't report how long it lasted >= 10 seconds?

Thanks for the link to that newsletter, ozij. I skimmed through the first 6 pages or so; lots of good info to take in, although I got confused at the "central hypopnea" term which did lead to central apnea. The more I think I am beginning to understand, the more I realize I do not know.

Does the S9 in Auto mode not raise pressure for an hypopnea event?

What about a central apnea event? Is pressure raised to try to help that, or not? I'm guessing "not" since a CA has the airway open, so increasing pressure wouldn't do anything?

Which leads me to ask, is the only event for which pressure gets raised an obstructive apnea event?

Well, if I'm figuring all that out correctly, then it makes more sense now that I see clusters of centrals in the morning hours, a few hypopneas, and just a few obstructed. I'm guessing that the S9 Auto took care of most of my obstructed, so only a couple make it to the >= 10 second mark, but more centrals and a few more hypopneas will be seen since nothing is or ought to be done to done with pressure increase to try to stop them. Rather, just report them. But if all that is true, then it still confuses me with centrals have the >= 10 seconds number assigned, but hypopneas do not.

Bump - I just did some updating to my wording in my post before this one to try to make more sense of my questions.

Jeffster wrote:Does the S9 in Auto mode not raise pressure for an hypopnea event?

It does not, though they are scored as precursor events which may impact the behaviour of the APAP if they are followed by an obstructive apena (depending on the timing etc)

Jeffster wrote:What about a central apnea event?

It does not.

Jeffster wrote:Is pressure raised to try to help that, or not?

Since a CA is not a closed airway event, raising "stint" pressure does nothing useful, and may trigger other unwanted responses. A different sort of device than a xPAP is needed to address significant, recurrent CA events.

Jeffster wrote:is the only event for which pressure gets raised an obstructive apnea event?

That effectively seems to be the primary case, though the specific details of the current Resmed treatment algorithm embedded in the S9 series machines have not been published, so there is a degree of reverse engineering from observed beahviours in any opinion on what actually determines flow rate incerases.

Jeffster wrote:But if all that is true, then it still confuses me with centrals have the >= 10 seconds number assigned, but hypopneas do not.

A hypopnea is a limitation in flow in the airway, which may occur in a number of differnt places for a number of differnt resaons, so knowing the duration is its less than 10 seconds doesn't really provide any much in teh way of useful clinical diagnotsic clues.

A central apnea is specifically a cessation in flow with no limitation in flow from the airway so it is quite a different event from a hypopnea and has pretty much just one reason, the brain didn't trigger a breathing action. Understanding the duration of a CA is useful for clinical diagnostic purposes, even ia xPAP system is unable to respond to the event.

Cheers,

Bill

If you haven't seen this ResMed video yet, now is a good time:
Understanding sleep disordered breathing
http://www.resmed.com/ap/multimedia/und ... 40x380.swf

And you will find the Autoset explained here:
http://www.resmed.com/au/clinicians/com ... clinicians

billbolton, thank you for the detailed responses. I feel a bit better now at understanding what I am looking at in my ResScan data.

ozij, thanks again for linking me to more very useful info.

And thanks cpaptalk.com for being here so that we may all try to understand our therapy better together.

Does the auto increase pressure in response to an obstruction before the ten-second mark?

Breathe Jimbo wrote:Does the auto increase pressure in response to an obstruction before the ten-second mark?

Resmed xPAPs will not increase pressure during any event.

Cheers,

Bill

billbolton wrote:

Breathe Jimbo wrote:Does the auto increase pressure in response to an obstruction before the ten-second mark?

Resmed xPAPs will not increase pressure during any event.

Cheers,

Bill

Wait, what? When does a Resmed xPAP increase pressure? How does it determine to stay at that pressure, or increase more if more max is available, or determine to go back down towards min pressure?

I incorrectly assumed my S9 was raising pressure during OA event until it got to the point that the pressure stopped the OA event.

Jeffster wrote: Wait, what? When does a Resmed xPAP increase pressure? How does it determine to stay at that pressure, or increase more if more max is available, or determine to go back down towards min pressure?

I incorrectly assumed my S9 was raising pressure during OA event until it got to the point that the pressure stopped the OA event.

Resmed's APAP's - like other APAP's raise the pressure after they have analysed the events in the context of the breaths preceding them. They will decide to raise pressure after having decided that that this is an event justifying a raise in pressure.
APAP also try to preempt the occurrence of obstructive events by responding to indicators that your breathing is being disrupted by imminent collapse of the airway.
For ResMed, those are snores, and flow limitations.
The pressure is raised for 20 minutes, and dropped back down if breathing has been nice and stable. If there are more "pressure raising triggers" (see the links I provided) the pressure will go higher. The maximum pressure is a high as it will go.

Edited for typos... .

ozij wrote:

Jeffster wrote: Wait, what? When does a Resmed xPAP increase pressure? How does it determine to stay at that pressure, or increase more if more max is available, or determine to go back down towards min pressure?

I incorrectly assumed my S9 was raising pressure during OA event until it got to the point that the pressure stopped the OA event.

Resmeds APAP's - like other APAP's raise the pressure after they hava analysed the events in the context of the breaths preceding them. They will decide to raise pressure after having decided that that this is an event justifying a raise in pressure.
APAP also try to preepmt the occureced of obstructive events by responding to indicatore that your breathing is being disrupted by imminent collapse of the airway.
For ResMed, those are snores, and flow limitations.
The pressure is raised for 20 minutes, and dropped back down if breathing been nice and stable. If there are more "pressrure raising triggers" (see the links I provided) the pressure will go higher. The maximum pressure is a high as it will go.

I have read some of the flow limitation and flow threads here in the past few weeks, have learned a bit more about it, and so I can begin to understand how that information, along with snores, is important to determine breathing problems. Thanks ozij for letting me know this, along with the 20 minute period.