Flow Limitations

[DariaVader]

One thing to keep in mind when considering hypopneas is that not all hypopneas are obstructive. Some are centrals.

Best Regards,

PaytonA

I had a very low central index on my study, and rarely show CA in sleepyhead - even with higher pressure and epr3 - so i dont think central is an issue for me, but good to keep in mind!

Respironics reports RERA in all data capable machines, so BiPAP yes. Resmed seems to have incorporated RERA into the Airsense 10 autosets, but I don't know about the Aircurve VPAP line.

Respironics' BIPAP (DS760) also has the option of using an auto-adjusted range of Pressure Support, rather than just a fixed value.

Good to know! I am leaning towards respironics equipment if I change machines for the better off-grid capabilities, if nothing else. From what I have read on this board, the differences in algorithm have to do with pressure pulses and adjustments, and I seem to be fairly impervious to those from a sleep disruption standpoint.

[iSnore]

If you go with Respironics, I recommend you buy the "TS" bundle, i.e. DS760TS. It comes with the DS6T heated tube humidifier (including heated tube) at a huge discount. AFAIK, Supplier #10 is perhaps the only one who carries it. The rest charge you the same as the prices of the CPAP and DS6T humidifier combined.

[DariaVader]

my insurance coverage is 100% of any equipment that is shown to be medically necessary - so DME it is - but going in informed will be better than how it was before. Then I was lucky they like to give the S9 Autoset I could easily be the proud owner of a brick. lol.

[vsheline]

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

[PaytonA]

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!

Best Regards,

PaytonA