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Flow limitation
#41
RE: Flow limitation
Flow limitation is not treated adequately by CPAP or even with the limited pressure support of EPR. Bilevel pressure support provides a mechanical assist by providing increasing pressure through inspiration to boost the flow rate and total inspired air volume with less respiratory effort by the patient. The end result can be similar to the wave form seen in individuals without upper airway resistance. It is the flow limitations that are the root cause of respiratory effort related arousals (RERA). Even mild or moderate resistance can cause sleep stage arousals you won't be aware of, but that contribute to daytime sleepiness and fatigue. With a real bilevel like the Vauto, we can tune pressure support, time of inspiration, and sensitivity of trigger and cycle to make respiration more normal with less effort. There will still be some episodes of flow limitation, but they should be less severe. At a minimum, we are attempting to reduce the 95% flow limitation to below 0.10, and would prefer less.
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#42
RE: Flow limitation
@DanEm

Interesting article.
How do you convert the Oscar flow limitation data to a percent of total sleep time?
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#43
RE: Flow limitation
I do not convert Flow Limitation data, it is just the way I show it.

Maybe the view below will be more to the point.

Each dot has AHI < 5 and Flow Limitation > 0.3 (30%)

   

DanEm

"If life hands you lemons, make lemonade! Words to live by, especially when you keep in mind that the only way to make them into lemonade is to squeeze the hell out of them."
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#44
RE: Flow limitation
Sorry, I hadn't connected that the flow limit number from OSCAR is a percent.
Percent of what?
I gotta go back and read a couple wiki articles again. 

It definitely looks like you have data to support switching to bi-level.
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#45
RE: Flow limitation
I like that chart of flow limitation by date. It certainly makes the problem obvious.

The only change I might make is to use the 95-percentile value for each day, rather than the 99.5-percentile value.

It would be easier to prepare these graphs if the daily CSV reports included the flow limitation value for ResMed machines...
Apnea Board Monitors are members who help oversee the smooth functioning of the Board. They are also members of the Advisory Committee which helps shape Apnea Board's rules & policies. Membership in the Advisory Members group does not imply medical expertise or qualification for advising Sleep Apnea patients concerning their treatment.
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#46
RE: Flow limitation
Quote:pholynyk
It would be easier to prepare these graphs if the daily CSV reports included the flow limitation value for ResMed machines...

?????????????

My machine is Resmed Airsense 11.
OSCAR daily export csv contains (among others)
  • 95% Flow Limit.
  • 99.5% Flow Limit.
  • Median Flow Limit.

DanEm

"If life hands you lemons, make lemonade! Words to live by, especially when you keep in mind that the only way to make them into lemonade is to squeeze the hell out of them."
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#47
RE: Flow limitation
Oh, so it does! It's been a long times since I looked a the Summary report, and even longer since I worked on the csv export routine.

Thanks for the update!
Apnea Board Monitors are members who help oversee the smooth functioning of the Board. They are also members of the Advisory Committee which helps shape Apnea Board's rules & policies. Membership in the Advisory Members group does not imply medical expertise or qualification for advising Sleep Apnea patients concerning their treatment.
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#48
RE: Flow limitation
My understanding (correct me if I am wrong) is as follows:

Since my machine has an EPR max of 3 cm, it is not enough to adequately control Flow Limitation.
The recommendation is a change for a BiPAP where the equivalent pressure assist is 10 cm.

So, if it is required that I get more than 3 cm EPR, the BiPAP can reduce the pressure by 10 cm although the principle for BiPAP is that pressure assist is added, not subtracted.
So the low pressure setting on a BiPAP could be set to 5 cm and with a pressure assist at 10 cm, the range for exhale pressure would be between 5 and 15 cm.

To get the same from my APAP, it would require an EPR of 5 cm with the low pressure setting at 10 cm (which is not possible).

I took a look at my EPAP and gathered data for the following conditions:
For all data shown there are no events (AHI =0 and RERA = 0).

The graph attached shows the results.

From the graph:
The EPAP range is from 0 to 20 cm.
The blue bars show when EPAP was near 7 cm.

The maximum FL is near 0.4 when EPAP is near 16 cm. Why did EPAP not go higher?

The FL is near 0.25 when EPAP is at 20. Why did EPAP got so high for a lower FL?


Attached Files Thumbnail(s)
   

DanEm

"If life hands you lemons, make lemonade! Words to live by, especially when you keep in mind that the only way to make them into lemonade is to squeeze the hell out of them."
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#49
RE: Flow limitation
Hello DanEm

"The FL is near 0.25 when EPAP is at 20. Why did EPAP got so high for a lower FL?"

If the Maximum Pressure you have set is at 20 and your EPR is 3 i don't understand how can your EPAP ever get to 20?

What were your settings on 31 August?

Not sure if I am following your logic or even understand how you produced your charts (impressed).


On 24 Jul 2020 in session #1 you maxxed out at 15 cmw and your FL remain high.

In Session #2 your increased Min Pressure (10 vs 6) and the combination of allowing pressures to go higher reduced your FLs.

In my case both Min EPAP and PS are needed to reduce FL. See post #5 in this thread mrsub96

I will be interested to see how this improves when you get your Vauto.

Maybe run some correlations on your 95FL and various pressures, min, median, 95% and so on?
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#50
RE: Flow limitation
Danem, this graph is very interesting and it appears that there is an inverse correlation between maximum EPAP and 95% FL.  This would be interesting to view as a ranked data-set. In other words, rather than order by date, order by increasing or decreasing pressure to see if the inverse correlation holds up. 

[Image: attachment.php?aid=44856]
Sleeprider
Apnea Board Moderator
www.ApneaBoard.com

____________________________________________
Download OSCAR Software
Soft Cervical Collar
Optimizing Therapy
Organize your OSCAR Charts
Attaching Files
Mask Primer
How To Deal With Equipment Supplier


INFORMATION ON APNEA BOARD FORUMS OR ON APNEABOARD.COM SHOULD NOT BE CONSIDERED AS MEDICAL ADVICE. ALWAYS SEEK THE ADVICE OF A PHYSICIAN BEFORE SEEKING TREATMENT FOR MEDICAL CONDITIONS, INCLUDING SLEEP APNEA. INFORMATION POSTED ON THE APNEA BOARD WEB SITE AND FORUMS ARE PERSONAL OPINION ONLY AND NOT NECESSARILY A STATEMENT OF FACT.
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