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Question about ResMed "For Her" algorithm - it only responds to OAs up to 12 cm?
#1
I have been reading about ResMed's "For Her" algorithm. I was looking at an article on the ResMed website (title and authors listed at the end of this post) and found the information below in Table 1 of the article.

It all makes sense to me, except for the part that says "the maximum pressure due to a closed airway apnea is 12 cm H2O. The therapy pressure still increases above 12 cm H2O if it is driven by either continued snoring or flow limitation. So the algorithm just ignores any apneas that happen after the pressure increases to 12 cm? Does this mean that the "For Her" algorithm wouldn't be a good fit for someone whose pressures typically go above 12 cm? Oh-jeez

Summary of AutoSet for Her therapy features and their relevance to female-associated OSA (adapted from Table 1 of article)

Female-associated OSA characteristics AutoSet for Her Therapy Feature

1. Women experience shorter obstructive events - Device includes RERA reporting to indicate the occurrence of respiratory events not strictly meeting the definition of an apnea or hypopnea.

2. Women are prone to more upper airway resistance and flow limitation - A single breath index is used to calculate and respond to the patient’s flow limitation (3 breath average used in standard AutoSet).

3. Women have predominantly REM-based events - If 2 apneas are detected within a minute, an ‘adaptive minimum pressure’ prevents therapy pressure decaying below this level for the remainder of the session. Minimum pressure will not exceed 10cmH2O.

4. Women require lower CPAP pressures than
males -
The maximum pressure due to a closed airway apnea is 12 cm H2O. The therapy pressure still increases above 12 cm H2O if it is driven by either continued snoring or flow limitation. This reduces the likelihood of reaching high pressures over short periods.

5. Women may experience more arousals from sleep - The algorithm contains several modifications to the internal gains of the algorithm which effectively result in a slower (and lower) pressure rise and decay when compared to standard AutoSet.




from Obstructive Sleep Apnea in Women: Specific Issues and Interventions
AJ Wimms, MSc Med; S Ketheeswaran, BBiomedSc; JP Armitstead, PhD
ResMed Science Center, Sydney, Australia
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#2
Nicely done. I think many people are under the impression that RERA reporting is the main difference.

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#3
(07-15-2016, 08:55 AM)green wings Wrote: It all makes sense to me, except for the part that says "the maximum pressure due to a closed airway apnea is 12 cm H2O. The therapy pressure still increases above 12 cm H2O if it is driven by either continued snoring or flow limitation. So the algorithm just ignores any apneas that happen after the pressure increases to 12 cm? Does this mean that the "For Her" algorithm wouldn't be a good fit for someone whose pressures typically go above 12 cm?

The full article is available on the manufacturer's website:
http://www.resmed.com/us/dam/documents/a...orithm.pdf

Hi green wings,

In any case, in the AutoSet For Her therapy mode, I suppose all Obstructive Apneas would still be reported, even when the pressure is above 12, so we would be able to see which OA events were being ignored.

I suppose the answer to your second question may depend on whether Obstructive Apneas are typically occurring when the pressure is higher than 12, rather than merely that our 95% pressure typically is higher than 12.

If one sees obstructive apneas commonly occurring at pressures above 12 and the rapid pressure adjustments of the ResMed standard AutoSet algorithm are not causing awakenings or excessive air swallowing or other problems, perhaps changing to the For Her algorithm would not result in a better fit.

But for users whose problem is the rapidity of the pressure adjustsments, or painful air swallowing or some other issue associated with high pressure, perhaps they would prefer the gentler For Her algorithm, even with the trade-off that above a pressure of 12 the For Her algorithm increases pressure only in response to Snore or Flow Limitation.

Take care,
--- Vaughn

Membership in the Advisory Member group should not be understood as in any way implying medical expertise or qualification for advising Sleep Apnea patients concerning their treatment. The Advisory Member group provides advice and suggestions to Apnea Board administrators and staff on matters concerning Apnea Board operation and administrative policies - not on matters concerning treatment for Sleep Apnea. I think it is now too late to change the name of the group but I think Voting Member group would perhaps have been a more descriptive name for the group.
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#4
Thanks for your comments, Vaughn. I'm still having a hard time getting my head around the "why" of no action by the "For Her" algorithm for OAs (or for hypopneas either, I suppose), although the article isn't completely clear about that.

In the description of "OA/hypopnea response" in Table 2 of the article describing auto CPAP algorithms, the response of the ResMed "For Her" algorithm to OAs & hypopneas is given as:

- Increases pressure based on current pressure every 10 s of apnea: increment max 2.5 when pressure is 4. Increment drops linearly down to 0.5 when pressure is 20

I'm assuming that description isn't correct, but I'm not clear about whether the increment drops linearly down to 0.5 when pressure is 12, or whether the increment drops as usual, but there's just no response after the pressure reaches 12.

I think I just need to try the algorithm for myself. Smile
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