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Uneven Flow Rate - Printable Version

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Uneven Flow Rate - Steptoe - 09-23-2021

[attachment=35919]I am concerned about the flow rate chart that is reported by Oscar.  As you can see from the attached screenshot, the flow rate shows numerous high deep breaths throughout the night.  From researching Oscar interpretation on the internet (primarily LankyLefty27 YouTube videos), it is my understanding that the top line should be such that you could put a straight edge on it.  In looking at Oscar screenshots that other people have posted in this forum, I don't see anyone that has the same flow rate issue that my Oscar results show.  

I started CPAP therapy in April with the DreamStation.  I purchased a Fisher & Paykel SleepStyle and started using it in mid-August because of the Philip's recall.  I am in the Oscar Beta test group for the SleepStyle and that is where the attached screenshot came from.  I had similar flow chart reports from Oscar, however, when I used the DreamStation. I am currently using a ResMed N30i mask.  I am a restless sleeper and I toss and turn throughout the night--from one side to my back to the other side, etc.  I can't really say that my sleep has improved since starting CPAP therapy, but my average AHI is now around 3, compared to 32 in my take home sleep study.  My AHI improved when I switched to the SleepStyle.

I am wondering why I have the uneven flow rate, and particularly am confused as to the the spikes that occur throughout the night.  Does this mean that I am being aroused or waking up when this occurs and is it a problem?  Does anyone see any other issues or concerns from what is being reported by Oscar that I should be aware of?

Thank you.


RE: Uneven Flow Rate - staceyburke - 09-23-2021

Your problem looks to me to be positional apnea. Positional apnea is when your chin drops down to your Sternum cutting off your own airway. You can NOT improve this with pressure changes, the only way to help is to stay out of that position. 

Many times it is sleeping on your back or too high of a pillow(s). If making changes don’t help many people have found using a
 Collar helps greatly. Please see the link in my signature about collars - it shows people without collars and the same people after they started using them. 

Your change of flow would be effected by your positional apnea.

RE: Uneven Flow Rate - GuyScharf - 09-23-2021

(09-23-2021, 11:50 AM)Steptoe Wrote: From researching Oscar interpretation on the internet (primarily LankyLefty27 YouTube videos), it is my understanding that the top line should be such that you could put a straight edge on it.

Dielaughing  Well, that's a fine theory but may not be the case in the real world. A person who does not have sleep apnea might have a flow graph that was a straight line on both the top and bottom. A straight line probably indicates even breathing. But nobody here is lacking in sleep apnea, and manifestations differ.

For example, my wife's flow curve (from an AutoSet) does have that flat line across the top for most of the night, but the bottom (exhalation) is fuzzy. She has an AHI usually above 2.0.

My flow graph (from a VAuto now and before that from an AutoSet) looks more like yours and is quite "fuzzy." My AHI is usually less than 0.4.

It's also possible you are seeing data artifacts either from the machine or from the way OSCAR has to process the flow chart for a SleepStyle machine. Zoom into one of those peaks that concern you to have about a two-minute scale and post a screenshot.

RE: Uneven Flow Rate - factor - 09-23-2021

Agree with the others but in general Jason means zoomed in on it should generally look level.  


RE: Uneven Flow Rate - Steptoe - 09-23-2021

I have attached three screeenshots:

1)  Two minutes where there was a high inhale flow, but no events.
2)  Two minutes where there was a high inhale flow, with an event.
3)  A three hour stretch where I am sure I was sleeping and where there were some high inhales w/o events and high inhales w/ events.

I see now that when I zoom in, the high flows that I questioned before don't seem so uneven.  The inhale (top) line seems much more straight.  I also see that some of the high lines in the flow chart coincide to times that I know I woke up or was awake.

I do see merit in the response that brought up the subject of "positional" apnea.  I slept on a different bed most of the summer (lake place) with a different pillow and I had lower AHI's than I get when I sleep in my bed at home (posturepedic mattress w/ flat CPAP pillow).  I have a very short neck. I mean very short, like head on shoulders.  I really don't want to wear a neck brace or any more apparatus to bed if I can avoid it.  After five months, I am still struggling with the mask and tubing, and I blame this for some of the problems I have in getting to sleep and frequently waking up.

As a side note, I am very happy with the Fisher & Paykel SleepStyle.  I bought it to use until my DreamStation was replaced (if ever), and with the idea of using it for travel and as a second machine at my lake place in the summer.  Now, especially with the availability of Oscar, I will probably use it as my full time machine, with the DreamStation 2 (if it ever arrives), serving as the backup.  I really do appreciate the ability to monitor my therapy with Oscar.

Thank you for the help and advice.


RE: Uneven Flow Rate - GuyScharf - 09-23-2021

I am not an expert on interpreting OSCAR reports, but I will offer these observations and guesses:

1) High inhale but no events: This does show variation in breathing. You breath shallowly and with gaps -- not quite apneas, then go back to breathing more deeply. This may be a cyclical pattern, but I don't see enough to say more. The variation and gaps in the flow aren't enough to trigger recognition as an apnea event.

You do have one artifact showing in this chart. Look at the far left edge and see how the flow diagram is rising from a lower level? That's not physically possible but instead results from the way OSCAR handles the flow data. OSCAR requires flow data that is centered around the zero line in the middle. I.e., air coming in is overall the same as air going out. Most CPAP machines report the data this way. The SleepStyle machine, however, always reports total flow, including intentional and unintentional leaks. The SleepStyle machine does also report the leak rate, so we subtract the leak rate from total flow to get the flow graph. Data in the flow graph is every 40 msec, but the leak data is only once per second. If there is a sudden change in flow rate that is not yet reflected in leak rate data, the flow diagram can go above or below the center line. When you see this, pay no attention to the details but do recognize that flow rate has probably changed suddenly.

2) High inhale but with three events: This is the easiest to interpret. The flow chart shows a sleep disturbance, then an event, then recovery breaths (which are larger). So maybe you were moving, turning over or something, holding your breath during the movement, and taking some big breaths afterward. A key point is that breathing is already disturbed before the event occurs.

3) Three hour stretch: I can't tell much from an overview.