AHI of over 20, but no large leaks: what's going on??

[niallm]

Hi folks,

I've been diagnosed about two years - a combination of central and obstructive. My machine's a Resmed S9 VPAP ST. Broadly speaking, the relatively mild therapy (IPAP 10/EPAP 6) has been effective and allowed me to function.

Over the past three months or so, however, my measured AHI has been getting steadily worse; see the Sleepyhead year overview for details (I'm not allowed to link directly to it by the board software (sigh) so I hope my attachment came through.

[attachment=913]

In particular, last night I had a reported AHI of 22 with a peak of 55 (?!), and I'm getting scared that something bad is happening but I don't know what it is:

[attachment=914]

There are a very large number of hypnopea events in the closeup, which I apparently can't show you.

There are no corresponding large leak events.

I am unable to understand what an even closer inspection is showing me (i.e. *how* it is bad).

I have no idea why this has started happening, or how to stop it.

I have not had sudden weight gain (I'm at about what I was when diagnosed).

I got a new mask a while back but it was the same model (Resmed Mirage FX) as the old one. Even if there was something up, surely it would manifest itself as a leak, which I don't have enough of.

How can I stop this getting worse? Help!

[robysue]

niallm,

The attachments came through.

What if anything happened around late April? Any changes in your health? Any new diagnoses that are NOT sleep related? Any changes in medication? Any head colds that you haven't been able to shake? Any respiratory problems? Summer allergies kick in? Any changes in your lifestyle? Change in diet? Change in exercise? Change in stress? Change in job? Are you sleeping on your back more? A lot more? Do you remember doing more dreaming recently?

Yes, I know a lot of that doesn't seem like it should be directly related to a worsening of the apnea, but sometimes anything that affects the sleep can affect the severity of the OSA.

And there's a pretty decided rise in the AHI that starts around late April, so it's reasonable to start by asking: What changed in your life?

And the max leaks look like they've gotten a bit worse. The 95% leaks are not so high as to be problematic, but they are high enough where it's worth asking: When's the last time you got a new mask?

In particular, last night I had a reported AHI of 22 with a peak of 55 (?!),

Last night's data does look bad:



It's possible that this is just a really, really bad night. And that things will get back to normal soon. But with that upward trend in the nightly AHIs, I think you're justified in being concerned.

and I'm getting scared that something bad is happening but I don't know what it is:

There are a very large number of hypnopea events in the closeup, which I apparently can't show you.

You have to zoom in on the Flow Rate curve and then take the screen shot. You can use the mouse to select the area you want to look at more closely. Or you can zoom in on the Flow Rate graph by LEFT clicking when the mouse is over the Flow Rate graph.

There are no corresponding large leak events.

This is NOT a surprise, while Large Leaks can lead to more events, Large Leaks are NOT caused by the events.

Still, we can rule out "Large Leaks lead to too little pressure which lead to too many events" as the cause of this nasty night's data.

I have no idea why this has started happening, or how to stop it.

When in doubt, it is time to consult your sleep doctor. Seriously: A three month increase in AHI that is not easily explained warrants a trip to the sleep doctor.

As for "how to stop it", that largely depends on what's causing the rise in AHI. It could be that for some reason your OSA has worsened and a bit more pressure is warranted. But it could also be that there's something else going on that needs to be investigated further by a qualified sleep doctor.

I have not had sudden weight gain (I'm at about what I was when diagnosed).

Weight is only one of many, many factors that go into determining the severity of the OSA.

Think carefully about what might have happened in your life around the end of April?

And have you had this kind of thing happen in previous summers, where the AHI winds up going back down after a few weeks?

How can I stop this getting worse? Help!

You need to consult your sleep doc about whether a pressure increase is needed. On the surface, that looks like it might be all that's needed. But pressure increases don't always resolve the problem: Sometimes there's something more subtle going on that needs a doctor's expertise. And you write:

I've been diagnosed about two years - a combination of central and obstructive.

The fact that you have a diagnosis of problems with central sleep apnea means that your situation is always going to be more complicated than someone who not had problems with central apneas.

In your case it looks like all that's happening is a whole bunch of H's are getting through. And the temptation is to simply assume all the Hs are obstructive in nature. (And in that case, a bit more pressure would be the thing to try.) But there are also some Unknown Apneas being scored and those UAs are scored when the leak is NOT in or close to Large Leak territory. And you say your diagnosis included some central apneas. Those two things taken together hint at the possibility that some of the current problem may be central in nature rather than obstructive. And if there is a central problem, more pressure might make things worse instead of better.

My honest opinion is that it's time to call the sleep doc and report what's happening. It's worth asking for a call back from the doc or his nurse/PA to talk about the data and ask them whether they need to see you in person. Personally given the trend in the data and the length of time things have not been going well, I'd say you need to make an appointment to see the doc (or his PA) as soon as you can be seen. I also think you should get a copy of the data you are seeing to the doc in advance of your appointment, along with a written note that you are concerned about the trends you are seeing in the daily detailed data.

[trish6hundred]

Hi niallm,
WELCOME! to the forum.!
You should see your sleep doc as soon as you can.
Best of luck to you as you try to figure this out.
Hang in there for more responses to your post.

[vsheline]

In your case it looks like all that's happening is a whole bunch of H's are getting through. And the temptation is to simply assume all the Hs are obstructive in nature. (And in that case, a bit more pressure would be the thing to try.) But there are also some Unknown Apneas being scored and those UAs are scored when the leak is NOT in or close to Large Leak territory. And you say your diagnosis included some central apneas. Those two things taken together hint at the possibility that some of the current problem may be central in nature rather than obstructive. And if there is a central problem, more pressure might make things worse instead of better.

Hi niallm, welcome to the forum!

You have an "ST" type of machine, which can be operated in ST mode and synchronize itself to your natural breathing rate but, if you fail to take a breath, is also able to step in with a backup breathing rate to help keep you breathing. It should be able to help treat your central events as long as the Pressure Support (PS) is high enough. The PS is the pressure boost your machine adds to help with inhalation. It is the pressure difference between EPAP and IPAP.

For example, when I am making too little or no effort to breathe, my ASV machine will increase PS to do for me most (or, if necessary, all) of the work of breathing.

I normally need PS to be around 4, but PS may need to automatically raise itself to 6 or 8 if it needs to do for me most of the work of breathing.

My ASV machine would NOT be able to treat my hypopneas and apneas if its Max PS setting or if its Max IPAP setting were to be too low and were to prevent it from being able to automatically raise PS high enough to treat my hypopneas and apneas.

In your case, IF THE HYPOPNEA CLUSTERS ARE CENTRAL in type (for example, if these are NOT accompanied by Flow Limitation), to treat your hypopneas the machine may need to use larger PS (by raising IPAP without changing EPAP).

Or, in your case, IF THE HYPOPNEA CLUSTERS ARE OBSTRUCTIVE in type (for example, if these ARE accompanied by Flow Limitation), to treat your hypopneas the machine may need to use larger EPAP without changing PS (by increasing IPAP by the same amount that EPAP is raised).

Or maybe you would benefit from increasing both EPAP and PS (by increasing IPAP more than however much EPAP is raised).

As robysue has pointed out, it is best to consult your doctor after emailing him your sleep reports.

However, SleepyHead is beta software and still has some bugs, and ResScan is bug free and will work with your ResMed machine, so I suggest it would be best to send your doctor ResScan reports (which he would likely be more familiar with, anyway) rather than SH reports.

Take care,
-- Vaughn

ADDED:

I've now investigated what types of settings your machine has. Your machine does not have settings for Max PS or Max IPAP because EPAP and IPAP are fixed settings on the ResMed VPAP ST, only manually adjustable.

So if the difference between EPAP and IPAP is too low, the machine will not be able to adequately treat central events on its own without at least some effort on your part. But, at the same time, if the difference between EPAP and IPAP is too large this might increase your tendency to have central events (even though the larger PS also helps to better treat the central events when they do occur). Likewise, increasing EPAP or IPAP or both may increase the likelihood of central events occurring.

Also, if PS is too large for too long, this could cause hyperventilation, which can be very unhealthy, causing too much oxygen in the blood, increasing oxidation and increasing the number of free radicals in the blood, leading to atherosclerosis and accelerated aging and other health problems, such as interfering with prescription medications. (A recording oximeter could be used to occasionally monitor SpO2, the saturation percentage of oxygen, overnight and verify that oxygen levels are, on average, in the mid-to-low 90's, which would be adequate without being too high.)

I suppose an ST machine works best when the "backup rate" change to IPAP triggers our own effort to breathe, interrupting the central event at its start, resulting in a normal strength inhalation. But in your case, during a central event, perhaps the machine's "backup rate" change to IPAP is not succeeding in triggering your breathing effort, and your machine's PS of 4 is too low to keep you adequately ventilated without some breathing effort on your part. Perhaps an ASV machine is needed?

Carefully slow and gradual optimization will likely be needed, since you may have a tendency for central events to occur (since you have been prescribed an ST machine which is usually not prescribed unless central events were predominant).

Is your machine set in "ST" therapy mode, or is it in plain "S" mode without a backup rate?

What is the percentage of Spontaneously Triggered Breaths (the percentage of breaths which you yourself started)?

What is the percentage of Machine Triggered Breaths (the percentage of breaths which the machine started because you had failed to initiate inhalation)?

What are the settings for Ti Min and for Ti Max (the minimum and maximum time limits allowed for inhalation)?

Does ResScan report how much Flow Limitation is occurring, and, if it does, is Flow Limitation occurring when the hypopnea clusters are occurring?

If your hypopnea clusters are not accompanied by Flow Limitation then I would think it likely that IPAP needs to be increased. In other words, if FL is not occurring then I think these are central events which can be helped by higher PS without changing EPAP. The higher PS will help directly to ventilate you at least a little more both before and during a central event, and the larger change to IPAP pressure may also help to better trigger your own breathing effort. (But in some patients a higher IPAP might also increase their tendency to have central events.)

If your hypopnea clusters are accompanied by Flow Limitation then I would think it likely that both EPAP and IPAP need to be increased by the same amount. In other words, if FL is occurring then I think these are obstructive events which can be helped by higher EPAP without changing PS. (But in some patients the higher EPAP and IPAP might also increase their tendency to have central events.)

But it is best to consult doctor before making changes. (Especially since some new condition may have started in April which may need to be diagnosed and treated.)

Take care,
--- Vaughn

[justMongo]

Robysue always has well reasoned answers; and best advice in this case is to see the doctor.
I don't think the S9 VPAP ST has the FOT algorithm. ergo: it cannot differentiate a CA from an OA.
Since it's a fixed pressure machine, it doesn't need the FOT to decide if an auto pressure adjust is indicated or contraindicated.
If all the scored HAs were removed, the night would look pretty good. An HA is a reduction in flow by more than X%. So, the attempt to breath is still there; it would seem flow limited. Just a stab in the dark, an increase in both IPAP and EPAP, keeping the same PS=IPAP-EPAP might mitigate the HAs.

Still best to show the data to your doc; and get a professional opinion.

All good questions from Robysue... what changes since April -- weight, meds...

By the way: why don't you use your humidifier? (in your profile)

[Skypilot]

Could the resmed be malfunctioning? Have the settings on the ResMed changed?

[justMongo]

Could the resmed be malfunctioning? Have the settings on the ResMed changed?

From the pressure and flow data, I think not.

[vsheline]

An HA is a reduction in flow by more than X%. So, the attempt to breath is still there; it would seem flow limited.

I think it cannot be concluded from the data posted that the attempt to breathe is still there during the hypopneas.

If the machine is operating in ST therapy mode it will use a backup respiration rate to switch back and forth between the EPAP and IPAP pressures (resulting in some tidal airflow) even if no breathing effort is being made. (Tidal airflow is the amount of air actually being inhaled or exhaled.) But if no breathing effort is being made, when the difference between EPAP and IPAP is only 4 cm H2O, this would probably result in less than half of his normal breathing tidal airflow. When eventually niallm again restarted his breathing effort, the return to a higher tidal airflow would cause the machine to report a hypopnea had ended. It is possible this is what is happening during the hypopneas.

It is also possible the hypopneas are, instead, obstructive and would be helped by increasing both EPAP and IPAP.

If the machine reports Flow Limitation data, that would be where to look to see whether the hypopnea clusters are central or obstructive in nature.

[diamaunt]

\
I don't think the S9 VPAP ST has the FOT algorithm. ergo: it cannot differentiate a CA from an OA.
Since it's a fixed pressure machine, it doesn't need the FOT to decide if an auto pressure adjust is indicated or contraindicated.

By the way: why don't you use your humidifier? (in your profile)

even the elites have FOT, and score OA and CA appropriately.

not everybody needs humidification, I only use it when I've got a head cold.

[vsheline]

even the elites have FOT, and score OA and CA appropriately.

Right, but the normal FOT includes a 6 second delay and then takes at least an additional 4 seconds to do.

My ResMed ASV machine does not report CA versus OA, because it doesn't take any time to determine the type of apnea; it just quickly jumps in with larger Pressure Support to keep me ventilated.

The ResMed VPAP ST would simply start switching between EPAP and IPAP, without taking the time to determine why a new breath had failed to start. It cannot afford to take any time to perform an abbreviated FOT determination of central versus obstructive.