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Oscar/Air report questions
Oscar/Air report questions
As a very new user of sleep information, I have some questions about the reports I see each day.

First, How does the Cpap machine or Oscar distinguish between Clear Airway and Obstructive Apenas?  Is there a mechanical aspect to this such as pressure to flow ratio changes or is it just an algorithm based on airflow patterns?

Second, What is the definition of flow limits (air supplied, air accepted, set by the machine etc.) and what is the significance in evaluating breathing.  I see comments like "there were flow limits throughout" that I am trying to understand.

Is there a Wiki somewhere for Oscar that would help me understand the data that the experts are using to evaluate situations?  There is a LOT of data in the Oscar reports that I am sure is important.  I would like to be able to learn more.

Thanks, I am not trying to become an expert Big Grin , just a more informed user. Please let me know if this is not the right place for these questions.

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RE: Oscar/Air report questions
The OSCAR wiki is here: http://www.apneaboard.com/wiki/index.php/OSCAR_Help

Flow limitations are events related to apnea, but is a partial blockage. To sense central or CA events, machines employ a way to send pressure pulses or forced oscillation technique (FOT). It's similar to sending an air "signal' when the machine notices you haven't taken a breath. It sends the pulse to measure resistance. No resistance equals a CA event flag.

Standard OSCAR Chart Order
Mask Primer
Dealing With A DME
Soft Cervical Collar Wiki
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RE: Oscar/Air report questions
Welcome to the forum

CA vs OA - ResMed sends a high-frequency pulse, think sonar, this detects blockage. Blocked means OA otherwise CA "Clear Airway" or Central APnea.

Flow Limits - Think of them as part of a continuum, Apnea, Hypopnea, Flow Limits, normal breathing. They are measured by a "flatness" index on ResMed. Many of us look at the Expanded Flow Rate curve to spot them.

There are various articles in the Wiki, Optimization, Treatment-Emergent Central Apnea, Soft Cervical collar, Flow Limitations, and a few others.

A better approach is to post your daily charts and ask for help with them. That keeps it to what directly impacts you.
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RE: Oscar/Air report questions
Thanks for that. 
So what am I looking at when I look at the Flow Limits display on Oscar?  The Y axis shows amounts from 0 to 1.  Is that the percent of blockage?  Another question.  What is the difference in  Pressure  and  Mask Pressure.  They both have the same shape.  Is one the limits set and the mask the measured pressure?  Thanks.
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RE: Oscar/Air report questions
Pressure is really Pressure settings. This is what we usually want to see.
Mask Pressure is literally mask pressure, It is a much higher frequency. Look at them in a 2 minute zoom when you are using EPR.

As I said before Flow Limits is a flatness index with a value of 0 to 1. The higher the number the worse the Flow Limitation. It has nothing to do with blockage. Flowlimits start at 50% airflow so 50-99% airflow or 1-50% "blockage" The lower value is not clearly defined anywhere. We must be careful to not chase flow limits when they have little to no impact on therapy. This varies by patient.
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RE: Oscar/Air report questions
I'm still confused about flow limits.  Looking at my  flow limit chart, it shows a reading of about .20 for about 12 seconds.  Would that constitute a flow limit or would it have to be .5 for at least 10 seconds (using the apnea definition)?
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RE: Oscar/Air report questions
I'm fairly new to the flow limitation game, I've done xPAP for 19 years and have know about flow limitations for a few months. Every now and then I'll do a little chasing to see how things change.

My understanding is that there is no mathematical calculation such as The number or flow limitations * or / The amount of airway restriction * or / The duration of events = The index number. If you are looking to quantify it, you're out of luck. I've looked and can't find any way to get there.

Typically my FL are around 0.4 at Max and they have always been 0.0 at Median and 95%. I did have one really bad night of not getting very good sleep unrelated to xPAP and my Max was 0.99; life happens and that blower on the nightstand is not a panacea. Max is pretty easy to figure out. On the graph I tracked it down to an event that lasted 12 seconds. Were there others that lasted 10 seconds? Probably. On any given night I will have multiple flow limitations that reach close to 1.00, but they may only last 5 or 6 seconds so they don't get scored. My Max for the night might show 0.35.

The way I look at it is because they were less than 10 seconds they are not counted, although they appear on the graph. This may seem worrisome at first, but after thinking about it, I might have 100 obstructive events that are less than 10 seconds that I am completely unaware of. With enough time and effort a person could go through a night looking at the Flow Rate and try to track everything down. But I've seen some unusual shapes that happen and there is nothing happening on the other graphs.

At the end of the day, I have to assess how I feel. Generally when my flow limit index is lower I tend to feel more refreshed. That said, when the number is 0.2, I'm not going to jump out of bed and run a marathon. Likewise on the 0.99 night I didn't feel that refreshed, but at least for me, I could go around my day and not need a nap. For someone else it might make the next day horrible.

I have read that a Max Flow Limitation of less than 0.3, (with 0.0 in all of the other columns), is a decent number, but everyone is different and that may not work for some people.

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RE: Oscar/Air report questions
There is no time involved, at least that I know of, but that was a good guess.
There are no stated numbers for what is good or bad. I look at the flow rate when flow limits are .25 to .33 + The question is there a therapeutic issue with the flow limits
A flow limit can be on a single breath, but that does not make it bad. With flow limits, I look at the shape of the breath on the flow rate, the flat or irregular top, the area under the curve is the volume more or less than normal breathing in the chart. Is there a series of consecutive flow limits? An Arousal following, stuff like that. All too often people chase flow limitations that are not symptomatically bothering them.

Take note that the medical industry pretty much ignores flow limitation, that is unless it is associated with significant RERAs, then they ignore the underlying flow limitations and just look at the arousals. A RERA is a series (not specified) of flow limitations that end in arousal.

check out this wiki.
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RE: Oscar/Air report questions
I guess my time assumption was incorrect. It was the only way I could possibly have a lower Max number and find higher index numbers on the graph.

It also seemed to be consistent with how a machine identifies any event. I figured there has to be some time span otherwise every 2 second swallow would be shown as a restriction.

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RE: Oscar/Air report questions
I checked last night's data. My Max index was 0.32. I found a flow limitation that was nearly 1.00 for 12 seconds. Based on that finding, it is obvious that time does not play any part in developing a Max index number.

So reassuring to know that for all the technology, the number actually doesn't mean anything other than a lower one is better.

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