Hypopneas vs. Flow Limitations

[apneaicinisrael]

Follow up question to a previous thread:

If my 420S registers "hypopneas", but doesn't have an integrated pulse oximeter (now wouldn't that be nice...), are these actually "flow limitations"? If so they sound much less bothersome. I have been unsettled by the relatively high hypopnea index that I get, though I feel good and the apnea index is below 2. Also, during my initial sleep study in the lab, I never had desaturations less than 89-90% during apneas. Just wondering...

Thanks, oh knowledgable people (or is that knowledgeable...)

AII

[Brent Hutto]

The sleep clinic where my studies were done use the following definitions:

"Hypopnea" is a reduction in flow accompanied by a desaturation.

"RERA" is a reduction in flow with no desaturation.

So by that reckoning your 420S is measuring something like an Respiratory Disturbance Index (apneas+hypopneas+RERAs) rather than an "AHI" (apneas+hypopneas). Flow limitation is a precursor state to apnea, hypopnea or RERA in which there is flattening of the flow-vs-time curve during the inspiratory period. It is my (limited) understanding that the Puritan-Bennett APAP algorithm (and presumably the monitoring software in your 420S) uses a fairly sensitive measure of flow limitation.

[ozij]

AII, the desats you had are significat - I think that if you were to have them while awake in a hospital, they'ld give you suplemental oxygen.

I had biiiiiig trouble inderstanding the difference between a "flow limitation" and a "hypopnea" on a PB.

The best way for me to understand it was via IFL1 and IFL2 in the CPAP's control screen. IFL1 shows you a graph of how a flow limitation looks - the shape of the flow over time changes. IFL2 shows a graph of how a hypopnea + flow limitation looks - different shape, and different height (volume I would guess).

A hypopnea without a flow limitation means less volume, without a change in the flow.

O.

[maxime]

hi
your desaturation is serious
89/90 is bad
take an oxygèn

and this 420s of goodnight is not a good engine because she is more slowly and bruyante
change your engine for an exemple a somnosmart of weinman

[Guest]

When the hypopnea vs. flow limitation definition/distinction was questioned previously, I found this post to be helpful:

Perhaps a light-hearted metaphor instead?

Apnea="the Grand Daddy of all obstructions"; the "big one" so to speak!

Hypopnea="baby" or "adolescent" obstruction; a lesser obstruction than apnea

Flow Limitation="zygote" or "fetus" obstruction; a lesser obstruction than even hypopnea; not yet a genuine obstructive problem for the vast majority of patients, but a significantly increased liklihood of becoming an obstructive breathing problem

Flow Limitation Run=several breaths, each impregnated with signs of "flow limitation"

[Guest]

Does the 420S have IFL1 and IFL2?

[Roger...]

I’ve struggled with understanding the definitions and meanings of these terms since I began getting hosed last October so I’m finding this thread interesting.

The sleep clinic where my studies were done use the following definitions:

"Hypopnea" is a reduction in flow accompanied by a desaturation.

"RERA" is a reduction in flow with no desaturation.

So by that reckoning your 420S is measuring something like an Respiratory Disturbance Index (apneas+hypopneas+RERAs) rather than an "AHI" (apneas+hypopneas). Flow limitation is a precursor state to apnea, hypopnea or RERA in which there is flattening of the flow-vs-time curve during the inspiratory period. It is my (limited) understanding that the Puritan-Bennett APAP algorithm (and presumably the monitoring software in your 420S) uses a fairly sensitive measure of flow limitation.

This was a really helpful outline.

Can you spell out the meaning of the acronym “RERA”?

AII, the desats you had are significat - I think that if you were to have them while awake in a hospital, they'ld give you suplemental oxygen.

or

your desaturation is serious
89/90 is bad
take an oxygèn

and this 420s of goodnight is not a good engine because she is more slowly and bruyante
change your engine for an exemple a somnosmart of weinman

When I had my sleep study done, my baseline saturation at that time was 92% and during the study a low of 79% was recorded. While I was ignorant at the time of the study about oxygen saturation, nobody seemed to get too worried about the baseline or the low saturation reading. Currently my Nellcor shows my initial baseline is 98%, but lows of 88% aren’t unusual during sleep.

Can either or both of you expand upon why you think oxygen would have been needed?

The best way for me to understand it was via IFL1 and IFL2 in the CPAP's control screen. IFL1 shows you a graph of how a flow limitation looks - the shape of the flow over time changes. IFL2 shows a graph of how a hypopnea + flow limitation looks - different shape, and different height (volume I would guess).

A hypopnea without a flow limitation means less volume, without a change in the flow.

Is there any chance you could post some images that show how IFL1 & IFL2 relate as you explain above? If you don’t have a place to post images, send them here and I’ll post them on a web server and post the URL in a follow-up message.

[Guest]

Roger, here's a link to a previous post by rested gal which includes a couple links to graphs representing IFL1 and IFL2 controls:

viewtopic.php?p=4708#4708

[rested gal]

RERA = Respiratory Effort Related Arousal (I think.)

Guest, you asked if the 420S has IFL1 and IFL2. Since the 420S is a straight cpap using a single pressure and doesn't have to make decisions about changing the pressure, I don't think it has those triggers...at least not both of them.

Description of the 420E autopap:
http://www.puritanbennett.com/prod/Product.aspx?id=265
"Detects inspiratory flow limitation with and without hypopnea to adapt to pressure needs and avoid increasing pressure on central hypopneas."

Inspiratory Flow Limitation is "IFL".
Without hypopnea - IFL1
With hypopnea - IFL2

Description of the 420S straight cpap:
http://www.puritanbennett.com/prod/Product.aspx?id=257
Doesn't mention detecting inspiratory flow limitation, etc.

"Must" reading for understanding IFL stuff are the excellent posts by -SWS:
Links to -SWS discussions

In those links, a good one to start with would be:
viewtopic.php?t=817

[Guest]

Found this while trying to learn what constitutes an RERA:

In 1999 the AASM Task Force defined RERAs (Respiratory Effort Related Arousals) as:
A sequence of breaths characterized by increasing respiratory effort leading to an arousal from sleep, but which does not meet criteria for an apnea or hypopnea. These events must fulfill both of the following criteria:

1. Pattern of progressively more negative esophageal pressure, terminated by a sudden change in pressure to a less negative level and an arousal

2. The event lasts 10 seconds or longer

RERA is a type of arousal, not a respiratory event.

[Guest]

autopaps cannot accurately detect hypoapneas as they are defined by the absm (1999), they can only estimate what they are based on volume changes and duration. The only machine able to detect a hypoapnea is the Resmed Spirit with the Reslink option. Then the Resmed machine doesn't detect hypoapneas, it considers them to be flow limitations.

In order to classify a hypoapnea as a hypoapnea, it has to be meet the following criteria:

decrease in air flow of 50%
lasting in duration >10 seconds
decrease in oxygen levels >3%

According to ABSM, if it doesn't have those 3 parameters it is classified as a flow limitation.

Since most autopaps are not equipped with Pulse Oximeters they can only estimate that they are hypoapneas.

PB420S: Unless you have some special 420S model, the S data model does not record sleep details using Siliver Lining software it only records basic compliance details similar to what the Remstar Pro delivers. I learned that the hard way. The E model records complete sleep details. The G model records nothing at all.

[ozij]

Sorry friends, I was in a hurry and quoted myself from another thread.
IFL1 and IFL2 pre se are irrelevant to the 420s - I had writtent that paragraph in a 420E context...

Rested Gal, maybe you can capture and post the pictures - in the advanced setup screen of the 420e, where you turn the IFLs on and off.

Another option Resmed: Three Lines of Defence You can see the way a flow limitation looks. A hypopnea (again, in PB terms) can be either an amplitude decrease in a normal breath, or a flow limitation+amplitude decrease.

O.

[ozij]

http://www.nda.ox.ac.uk/wfsa/html/u05/u05_003.htm

The alarms usually respond to a slow or fast pulse rate or an oxygen saturation below 90%. At this level there is a marked fall in PaO2 representing serious hypoxia.

http://www.aacn.org/aacn/practice.nsf/F ... 4%20PO.pdf

However, there is also this:

http://www.mayoclinic.com/health/oxygen ... on/AN01016

An estimate of your oxygen saturation can be made with a clip (pulse oximeter) that fits painlessly on your finger. No blood is needed for this test. The device shines a red light through one side of your finger and measures the light that comes through to the other side. Red blood cells that are saturated with oxygen absorb and reflect light differently from those that are not. If a more precise measurement is needed, oxygen saturation can be measured in blood drawn from your radial artery, which is located on the inside of your wrist.

Normal values for oxygen saturation can vary by lab, as well as other factors such as age, sex and altitude. Check with your doctor for the optimal values for your specific situation.

http://www.webmd.com/hw/health_guide_atoz/sto167663.asp

Oxygen saturation can be measured by a device called an oximeter. If oxygen saturation is less than 90% for long periods of time, it can cause several health problems, such as heart failure

.

Long periods is not an occasional dip.

http://www.nda.ox.ac.uk/wfsa/html/u12/u1203_03.htm

Oxygen Therapy

The American College of Chest Physicians and National Heart, Lung and Blood Institute published recommendations for instituting oxygen therapy. These include:

<snip>
Hypoxaemia (PaO2 < 59mmHg (7.8 kPa), SaO2 <90%)

O.

[rested gal]

Rested Gal, maybe you can capture and post the pictures - in the advanced setup screen of the 420e, where you turn the IFLs on and off.

[Guest]

This is a fascinating topic. Having learned a bit about Puritan Bennett's apnea/hypopnea detection system, I thought it might be interesting to read about the Respironics system as well. Here is a link to the patent for the Respironics Apnea/Hypopnea Detection System and Method:

Respironics Apnea/Hypopnea Detection System and Method