08-01-2015, 01:39 PM
(This post was last modified: 08-02-2015, 09:59 AM by vsheline.)
(07-31-2015, 12:56 AM)AshSF Wrote: Conventional wisdom says there are multiple stages of your airway's compromise:
1) When your airflow rate starts decreasing, it shows as flow limitation.
2) it reduces further and typically causes a RERA in most individuals.
3) if RERA is not induced to correct the airway patency, it becomes a hypopnea.
4) If it collapses further, it will become an obstructive event.
Your machine (S9) reports all of stage 1 and 2 as flow limitations. Why it doesn't show an FL of 1 before an O event is beyond my level of competence.
A Flow Limitation score of "1.0" would mean the shape of the Flow plot ("Flow" is the estimated rate of air entering our airway during inhalation and exiting our airway during exhalation) looks precisely like an idealized Flow Limited shape. An idealized Flow Limited shape would show a very short period at the start of inhalation where the Flow would start to rise normally but then the Flow would immediately drop and level off at a lower amount of Flow, and the Flow waveform would remain flat at the lower (but still positive) rate during the remainder of the inhalation portion (positive portion) of the Flow waveform.
Respiratory Effort Related Arousal (RERA) is an arousal caused by needing to exert excessive effort during inhalation because of a type of partial obstruction in the airway which occurs only during inhalation, only while we are trying hard to suck air into our lungs. The suction and the "venturi" action of the airflow through our airway cause our airway to narrow, limiting the rate at which we can inhale air, just like trying to suck harder through a weak or soggy straw will tend to cause the straw to close off further. The amount of effort we had been exerting had been sufficient to maintain the Flow at a level which was high enough that an hypopnea was not scored, but the Flow Limitation and effort eventually resulted in an arousal (RERA). In turn, the arousal (RERA) would have brought a short period of increased Flow until we returned to a deeper level of sleep.
Conceptually, RERA is by definition already an obstructive event, but not one of the events which are counted in the AHI.
RERA events are counted in the Respiratory Disturbance Index (RDI). Therefore, the RDI is a better indicator of sleep quality than AHI.
RDI = AHI plus the average number of RERA events per hour
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.
I think that you could look at apnea events as a narrowing of the normal (somewhat) flow wave form until it becomes a flat line or nearly so. Now you have an apnea. If the wave form only narrowed part of the way to a flat line (within the limits defined for a hypopnea), then it would be scored as a hypopnea.
Flow limitations are, as it has been indicated, a change in the shape of the wave form that results in a reduction of the flow. Not as much of a reduction as a hypopnea and apparently reduced differently.
At least those are my thoughts!