how do you spot hypopneas in OSCAR?

[WarmHoney3650]

is it true that resmed and most other cpaps are bad at spotting hypopneas? 
how do I look for them myself, by looking through OSCAR data? do the peaks and troughs just basically become progressively smaller?

[Gideon]

Simple version is that The algorithm that identifies various events does so by comparing flow rate amplitude against a moving average. It is possible, though uncommon for the events to be so consistent that they are missed. Hypopneas represent a 50-80%reduction in volume. In other words you are breathing 20- 50% of your normal volume. If this is the case you likely have severe lung issues.

Much more likely you are missing flow limitations which are less severe and are often identified via the shape of the waveform.

[Sleeprider]

As Gideon says, the CPAP machines simply identify a reduction in respiratory flow rate of 50-80%, while clinical hypopnea criteria are normally both a reduction in flow and a 3% to 4% reduction in SpO2.  I disagree with the premise that the machines are "bad at spotting hypopnea".  The machines simply place a flag when the criteria are met to do so. Analysis beyond that is more complex.  Hypopnea can be obstructive, central or mixed, however it can be very difficult to distinguish the class of hypopnea without also interpreting the flow rate, flow limitation and sometimes periodic breathing.  Leaks can also result in significant reductions in recorded flow-rate, and it appears that the machines have some compensation for leaks.  

Studies that compare automatic event detection (AED) in PAP machines have compared manual event detection in PSG. Respiratory Event Detection by a Positive Airway Pressure Device  This study suggest good correlation between AED and MED, with an event rate (AHI) less than 10.0 being highly predictive that the manually scored PSG AHI wOn the other hand, an AHI ≥ 10 events/hr by AED was only moderately predictive that the PSG AHI was ≥ 10 events/hr (positive predictive value = 67%). The event-by-event analysis showed that AED detection had a high specificity but only modest sensitivity (high number of false negatives)as < 10 events/hr.  Read the article for more detail.

[WarmHoney3650]

why is a hypopnea different to a flow limitation? is a flow limitation where reductions in airflow can  cause arousals, or is this a RERA?
can flow limitations cause symptoms?

[WarmHoney3650]

this is my flow limitation graph from last night. how normal does this look?

[OpalRose]

Removed your image as it was corrupted. Please repost your data using the Attachment Feature.

[WarmHoney3650]

   
this is my breathing pattern throughout most of the night... not sure if anything is wrong..

   

[Sleeprider]

Please post a full night of the Detail view with the Daily Sidebar (F8) statistics included.
There is nothing "wrong" with the example you provided. Flow limitation was present during portions of that segment, especially immediately after the hypopnea. The event shows a momentary pause in breathing after an exhale, followed by a smaller amplitude resumption of breathing with clear inspiratory flow flattening, before resuming normal respiration.

[WarmHoney3650]

see pic

[Sleeprider]

With this more expanded view and finally the respiratory statistics, we're looking a very good therapy at 11/8 pressure, just under 2-AHI nicely distributed between CA, OA and H events. Events are distributed through time without clusters to suggest positional issues. The hypopnea trend with minor flow limitation. There are a lot of positive things happening here, and this is giving us a strong clue you are nearly optimized, but with room for improvement in the obstructive events. I'm thinking a bump in pressure to 11.4 cm will accomplish a reduction in FL, H and O events, and the CA events may just be arousal artifacts. We don't want big changes, just a slight tweak closer to optimum settings.