Hypopneas ... almost ignored by Resmed

[Arizona-Willie]

Resmed says they mark a hypopnea after a reduction in volume of at least 50% for 10 seconds. They say they mark an apnea after a reduction of 75% or more for 10 seconds or more.

In the Rescan software they tell you how long the apneas last but they don't tell you much about hypopneas. They say they mark them after 10 seconds but that is all they say.

A hypopnea by their definition is a reduction of at least 50% --- but it can go up to 75% and then it is called an apnea.

And, it can last much longer than 10 seconds. There is no limit on length of a hypopnea before it becomes an apnea only a set point on volume reduction.

So a hypopnea can easily be a reduction in volume of 70% for 2 or 3 minutes ... or more ... which would be much worse than a 10 second hypopnea.

It seems to me that they aren't paying sufficient attention to hypopneas ... they just kinda wave them off with a casual ' oh that's just a hypop '.

I've been trying to work backwards in an Excel spreadsheet to work with the indexes and times they do bother to tell us and have been able to come up with a good count on apneas and hypopneas as far as their numbers go ( sometimes off by 1 which I attribute to rounding problems ). But not having much luck figuring out the average length of hypopneas and apneas.
I keep coming up with the exact same average length in seconds for both types.

Never claimed to be a math genius

Does anyone know how to find out the length and severity of hypopneas from Resmed data?

It seems to me that a long hypopnea can be just as damaging as a relatively short apnea ... or worse. But they ( Resmed ) don't seem to be all that concerned with them. They just focus on apneas.

[Wulfman]

It's my understanding that besides Apneas, ResMed machines focus on Flow Limitations (which would probably include hypopneas).......in addition to the snores, leaks, etc. In other words, they don't differentiate hypopneas from flow limitations and/or lump them together.This is apparently why so many people reading their ResMed reports or LCD screen data and question the higher AHI even though their AI is low.

Den

[Snoredog]

That is because that machine does NOT respond to Hypopnea at all.

From Resmed website:

AutoSet Algorithm
Increases pressure in response to the severity of the three parameters (inspiratory flow limitation, snore, and apnea):

The greater the flow limitation, the more pressure delivered
The louder the snoring, the more pressure delivered
The longer the apnea, the greater the increase in pressure


Normalizes sleep while delivering a mean pressure typically 37% lower than fixed pressure therapy.1

Where does it say it responds to Hypopnea? It doesn't, only to the above 3 events.

A Hypopnea is still classified as a 50% reduction in flow lasting >10 seconds or longer with an associated drop in SAO2 of 3%. Since that machine doesn't have a pulse oximeter as standard equipment to determine that 3rd requirement it only uses the first 2 (50% reduction lasting >10 seconds) so technically, those events classified as Hypopnea on this and other machines are false and those events showing up as Hypopnea are technically Flow Limitations unless it has that pulse oximeter to determine it as such.

A mfg might modify "its" parameters to classify an event compensating for sensitivity of the machine, but it doesn't change what classifies the event, that is determined by AASM/ABSM.

What you see on the LCD display or in the reports as HI or Hypopnea the machine probably responded to them during the Flow Limitation state and what you are observing is calculated after the fact.

[Treesap]

I have Resmed machine, and I often wonder about the HI as well. I always have some HI each morning. This morning it was 3.7, and no AI of course. I feel like poop this morning. I"m on Provigil, and I'm wondering WTF??? My pulmonologist had me take home an oximeter to use while I was on CPAP, and there was no reduction in my oxygen levels.

I think I need to get another machine...

[Snoredog]

I have Resmed machine, and I often wonder about the HI as well. I always have some HI each morning. This morning it was 3.7, and no AI of course. I feel like poop this morning. I"m on Provigil, and I'm wondering WTF??? My pulmonologist had me take home an oximeter to use while I was on CPAP, and there was no reduction in my oxygen levels.

I think I need to get another machine...

you show your pressure at 9.8 cm? What is your Minimum set to?

Is AI = 0.0? or does it show 0.8 or 0.6 or 0.4? If it is 0.0 you probably have your Minimum set too high. How you feel probably has no relation to your AHI. Your AHI looks fine, I would search for the pressure where you feel consistently better. I would only use the AI of the AHI as a guide, on that machine HI doesn't really mean anything. If AI = 0.0 you are probably too high on pressure.

[Arizona-Willie]

I have the CMS-50E pulse oximeter and it not only records the number of desat events, it also tracks < all > time below certain percentages whether each occurrence lasted the required 10 seconds to constitute and event or not.

It shows the percentage of time below 100 / 95/90/85/80 percent etc. etc.

My sleep doc never seems too concerned about the number of apneas / hypopneas ... he is always looking at the percentage of time below 90%.

Last night my time below 90% was 1.3% ... not too bad for me. I almost always have some time below 90.

I think the sleep doc's thinking is that you can have apneas and hypopneas and flow limitations but the reason we are concerned about those is because they cause SO2 desats.

So, rather than worry about the absolute numbers he concentrates on whether or not I am keeping my oxygen level up.

You can have an apnea / hypopnea and not have a desat because the event doesn't last long enough to cause the 02 level to drop.

The machines catch them and mark them, but unless you have one that has the ability to track your O2 they don't know about desats.

Having a separate pulse oximeter is a 2nd best situtation. We have to compare the results of the blower software with the results of the oximeter software because apneas / hypopneas by themselves are not the only thing.

It is possible to not have any apneas and still have a desat because of shallow / slow breathing.

I believe some of the high end Resmed machines allow you to force a certain number of breaths per minute and a certain volume.

But the low end machines will just accept shallow breathing as normal and use that volume to compute whether you have an apnea.

Naturally, apneas / hypopneas/ flow limitations are more worrisome for shallow breathers and cause desats much more quickly.

If you can get a recording pulse oximeter, the most important number of all is the percentage of time below 90%.

Ideally a person shouldn't go below 95% and below 90% becomes worrisome and we should try to stay above 90% at all times.

Recording pulse oximeters should be a standard part of SDB therapy.

I possibly need one of those high end machines. I know I have a slow breathing problem. I was having an MRI at Mayo and was very relaxed, not asleep but very close to going to sleep, and the tech came and told me to breathe faster. She said I was only breathing 7 times a minute and the machine needed me to breathe at least 11 times a minute. It was taking too long because they take a slice every time your chest gets to a certain position in the breathing cycle.

[Treesap]

you show your pressure at 9.8 cm? What is your Minimum set to?

Is AI = 0.0? or does it show 0.8 or 0.6 or 0.4? If it is 0.0 you probably have your Minimum set too high. How you feel probably has no relation to your AHI. Your AHI looks fine, I would search for the pressure where you feel consistently better. I would only use the AI of the AHI as a guide, on that machine HI doesn't really mean anything. If AI = 0.0 you are probably too high on pressure.

I am using my maching in CPAP mode. I did increase my pressure up to 11 to see how I felt. I have my ramp set at 8 right now. When I used the machine in Auto mode, my pressure almost always ranged 10.2 or below. I thought if I had it slightly higher, it would "cover" me. Maybe my thinking isn't quite right on that. I almost never see AI recorded. The few times I do, it's usually .2.

So do you think I should lower my pressure?

[Snoredog]

you show your pressure at 9.8 cm? What is your Minimum set to?

Is AI = 0.0? or does it show 0.8 or 0.6 or 0.4? If it is 0.0 you probably have your Minimum set too high. How you feel probably has no relation to your AHI. Your AHI looks fine, I would search for the pressure where you feel consistently better. I would only use the AI of the AHI as a guide, on that machine HI doesn't really mean anything. If AI = 0.0 you are probably too high on pressure.

I am using my maching in CPAP mode. I did increase my pressure up to 11 to see how I felt. I have my ramp set at 8 right now. When I used the machine in Auto mode, my pressure almost always ranged 10.2 or below. I thought if I had it slightly higher, it would "cover" me. Maybe my thinking isn't quite right on that. I almost never see AI recorded. The few times I do, it's usually .2.

So do you think I should lower my pressure?

increase pressure too much and it can result in unstable sleep, that feels like no sleep at all.

[Velbor]

True, ResMed machines do not track the duration of hypopneas as they do duration of apneas. (The older AutoScan software can export to Excel a minute-by-minute listing of apneas and hypopneas. The apneas are tagged with duration times. The "duration" of hypopneas is uniformly reported as zero. Current ResScan software does not provide this data export function.)

And true, ResMed's auto algorithm does not respond to hypopneas "per se."

But to simply say that ResMed "ignores" hypopneas is more than a bit of an oversimplification. ResMed in fact uses "flattening" as a surrogate for "flow limitation" which is a surrogate for "hypopnea". They state quite clearly why they choose not to respond to hypopnea.

The AutoSet algorithm adjusts treatment pressure as a function of three parameters: inspiratory flow limitation, snore, and apnea.

The flow sensor, located in the AUTOSET SPIRIT unit, enables detection of inspiratory flow limitation and apneas. The pressure sensor, also located in the unit, 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 unit as a function of time shows a typically rounded curve for each breath.

As the upper airway begins to collapse, the shape of the inspiratory flow/time curve changes and the central section flattens.

The AutoSet algorithm analyzes the shape of the central part of the curve for each breath and assigns a value as the amount of flattening.

Inspiratory flow limitation, or partial airway closure, usually precedes snoring and obstruction. Detection of this flow limitation enables the unit to increase the pressure before obstruction occurs, making treatment pre-emptive.

The Flattening Index 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. ....

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 15 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.

Not all forum participants may "like" or "agree with" all aspects of ResMed's algorithm, but there is little justification in implying or suggesting that ResMed "ignores" hypopneas. Hypopneas are clearly defined by ResMed (as indicated above -- clearly with no reference to oxygen desaturation) and the HI (number of hypopnea events per hour -- without reference to duration -- just as the AI makes no reference to duration) is computed and displayed. ResMed has opted (for clinical reasons) not to have its AutoPAPs respond to hypopneas themselves (just as they have opted not to respond to apneas at pressures above 10cm). There have been MANY discussions on this board as to the relative merits of different manufacturer algorithms. All have their own benefits and pitfalls. All work effectively for MOST patients.

The above comments (except for the quotation from ResMed literature) are my own. I do not speak for or on behalf of ResMed. Other than my own use of a ResMed machine, I have no relationship (business, employment or financial) with ResMed.

Velbor

[Engransan]

OK now I'm concerned. Have I put too much emphasis on lowering my Hypopneas? I have gradually increased my pressure to the present 14.2 with a corresponding decrease in hypops. Am I going too far? My Excel data file is available at
http://www.yousendit.com/transfer.php?a ... f3ef4ab2cc
Would you folks mind critiqueing it for me?
Thanks
Engransan

[Arizona-Willie]

I took a peek at your file and I'm wondering something.

What software are you using with your card reader?

How are you getting it to report the total number of apneas and hypopneas?

I have both the old Autoscan and Rescan 3.5 and neither one of them will show me the total number of apneas or hypopneas as far as I have been able to figure out.

Perhaps the Autoset reports that data and the S8 Elite doesn't?

I know how to export to Excel with Autoscan but have not seen a way to do it with the newer software.

Are you exporting or manually entering data on the spreadsheet?

[RiverDave]

Willie,

Multiply HI by time slept (converted to decimal hours => 6:30 = 6.50). This won't give you the exact value, but it will be pretty darned close. The reason it is not exact is that Resmed truncates the values at 1 decimal place instead of rounding them.

[Dennisla]

I took a peek at your file and I'm wondering something.

What software are you using with your card reader?

How are you getting it to report the total number of apneas and hypopneas?

I have both the old Autoscan and Rescan 3.5 and neither one of them will show me the total number of apneas or hypopneas as far as I have been able to figure out.

Perhaps the Autoset reports that data and the S8 Elite doesn't?

I know how to export to Excel with Autoscan but have not seen a way to do it with the newer software.

Are you exporting or manually entering data on the spreadsheet?

I've got the Autoset with Autoscan and Rescan 3.5 but cannot export data.
But It would be nice to find a way to convert the .rlk files into a readable format for excel.
Dennis

[Engransan]

I have the Rescan 3.5 but don't have a reader yet. I manually extract my data and enter it every morning into the Excel file. The Apnea total is calculated by Excel as AI x Hrs Sleep.
The Hypopnea total is calculated by Excel as HI x Hrs Sleep.

Am I overdoing the Minimum Pressure Setting and defeating the purpose of the APAP??

[RiverDave]

Engransen,
Yes, you are overdoing the minimum.

In my opinion, you are not using APAP at all. Your minimum and 95% pressure are essentially identical once your minimum hits about 13.6. To me this means you are running at a fixed pressure (or pretty close to it).

Your numbers are still a little crazy. Could be that you aren't used to the treatment because you keep changing your settings. Your best combination of leak, AI, AHI and HI was a pressure of 14, though (note that this was based on only 5 data points).

If it were me, I'd be using CPAP at 14 or APAP 12 to whatever (no need to cap the upper end).

Get other opinions, though. I'm mostly guessing.