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Why is Flow Limit very low for OA event?
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Ed1101 Offline

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Post: #1
Why is Flow Limit very low for OA event?
I have few OA (<25 total in two months) mostly CA and H. My AHI average last 7 days is 0.42. My question is obviously one of curiosity. See the chart Link
http://tinyurl.com/CA-OA-Chart1

It does not matter how slowly you go as long as you do not stop. --Confucius
03-26-2016 02:01 PM
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robysue Offline
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Post: #2
RE: Why is Flow Limit very low for OA event?
Those are "frank" apneas. That's why there's no increase in the FL graph.

The FL graph is based on the overall shape of several inhalations that have just occurred. In the picture you post, the inhalation shape remains nice and round right up to when the breathing stops. The size of the inhalations is decreasing, but their shape does not change. Had the breathing not stopped, but the very small, but well shaped inhalations continued for several more breaths, your machine would likely have scored an H without any increase in the FL curve.

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03-26-2016 02:18 PM
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0rangebear Offline

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Post: #3
RE: Why is Flow Limit very low for OA event?
(03-26-2016 02:18 PM)robysue Wrote:  Those are "frank" apneas. That's why there's no increase in the FL graph.

The FL graph is based on the overall shape of several inhalations that have just occurred. In the picture you post, the inhalation shape remains nice and round right up to when the breathing stops. The size of the inhalations is decreasing, but their shape does not change. Had the breathing not stopped, but the very small, but well shaped inhalations continued for several more breaths, your machine would likely have scored an H without any increase in the FL curve.

Please explain the term Frank Apnea

2004-Bon Jovi
it'll take more than a doctor to prescribe a remedy

Observations and recommendations communicated here are the perceptions of the writer and should not be misconstrued as medical advice.
03-26-2016 03:36 PM
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justMongo Offline

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Post: #4
RE: Why is Flow Limit very low for OA event?
FL is a scoring of the inhalation waveform. It flat-tops with partial obstruction. Auto machines like mine raise pressure on FL to prevent OA.
Sometimes FL does not precede an OA. The airway just collapses.

If I may presume to interpret for RobySue: A frank apnea is one that just appears without warning.
Sort of "frankly, I'm here!"

(And there is no inhalation waveform to score for waveshape)

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.
03-26-2016 04:04 PM
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robysue Offline
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Post: #5
RE: Why is Flow Limit very low for OA event?
(03-26-2016 04:04 PM)justMongo Wrote:  FL is a scoring of the inhalation waveform. It flat-tops with partial obstruction. Auto machines like mine raise pressure on FL to prevent OA.
Sometimes FL does not precede an OA. The airway just collapses.

If I may presume to interpret for RobySue: A frank apnea is one that just appears without warning.
Sort of "frankly, I'm here!"
Exactly!

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03-26-2016 04:14 PM
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Ed1101 Offline

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Post: #6
RE: Why is Flow Limit very low for OA event?
Thanks for the info. Virtually all my OA must not be Flow limit induced. ResMed 5.5 does not show any flat toping on the flow limit wafeform where an OA is flagged for any OA I have sense I started APAP. Not sure the significance of this but I suppose with AHI < 5, I'm OK. thanks

It does not matter how slowly you go as long as you do not stop. --Confucius
(This post was last modified: 03-26-2016 04:21 PM by Ed1101.)
03-26-2016 04:19 PM
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vsheline Offline

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Post: #7
RE: Why is Flow Limit very low for OA event?
(03-26-2016 04:19 PM)Ed1101 Wrote:  Thanks for the info. Virtually all my OA must not be Flow limit induced. ResMed 5.5 does not show any flat toping on the flow limit wafeform where an OA is flagged for any OA I have sense I started APAP. Not sure the significance of this but I suppose with AHI < 5, I'm OK. thanks

Hi Ed1101,

Flow Limitation is, by definition, something that happens during inhalation. If there is no Flow (if there is complete apnea) then the Flow is stopped rather than merely limited.

FL may occur during hypopnea, and may occur before or after complete apnea, but cannot occur during complete apnea.

FL occurs in a partially-obstructed airway when the reduction in pressure (slight vacuum) which occurs because we are breathing in, is enough to cause the airway to partially close off even worse. As we exert greater effort, the Flow may stay the same or even be reduced. This causes the "flattening" of the shape of the Flow waveform during our inhalation.

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.
(This post was last modified: 03-26-2016 04:53 PM by vsheline.)
03-26-2016 04:47 PM
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palerider Offline

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Post: #8
RE: Why is Flow Limit very low for OA event?
(03-26-2016 03:36 PM)0rangebear Wrote:  
(03-26-2016 02:18 PM)robysue Wrote:  Those are "frank" apneas.

Please explain the term Frank Apnea

"frank" is a medical term meaning "obvious". there's a person on the other board who misuses the term constantly as 'sudden' and i believe RobySue picked up that misuse.


Medical Definition of frank

: clinically evident <frank pus> <frank gout>
03-26-2016 05:54 PM
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