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+--- Thread: Why is Flow Limit very low for OA event? (/Thread-Why-is-Flow-Limit-very-low-for-OA-event)
Why is Flow Limit very low for OA event? - Ed1101 - 03-26-2016
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
RE: Why is Flow Limit very low for OA event? - robysue - 03-26-2016
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.
RE: Why is Flow Limit very low for OA event? - 0rangebear - 03-26-2016
(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
RE: Why is Flow Limit very low for OA event? - justMongo - 03-26-2016
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)
RE: Why is Flow Limit very low for OA event? - robysue - 03-26-2016
(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.Exactly!
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!"
RE: Why is Flow Limit very low for OA event? - Ed1101 - 03-26-2016
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
RE: Why is Flow Limit very low for OA event? - vsheline - 03-26-2016
(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.
RE: Why is Flow Limit very low for OA event? - palerider - 03-26-2016
(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>