Erroneous AHI / OSA event flag(s)

fog.apnea wrote:I was wondering (perhaps questioning) the accuracy of the xpap device's reporting of the AHI events based on my following observations and would like to hear feedback

- I have averaged 0.95 AHI overall in the past 80 days and I occasionally review overnight video recordings ((trending to less frequent as I have a good grasp on my sleep pattern now) of my sleep. I noticed that the few AHI events (mostly obstructive) that are flagged are pretty much while turning and rolling in the bed. I am sure there are real ones but am pointing out ones that aren't (likely). There are couple instances that I could clearly see breathing (can clearly see chest movement) even though obstructive event was recorded.
- I usually don't take naps but one day I tried to though ended up taking the hose off after 30 mins without actually dozing off. So obviously I didn't sleep for that period but SH showed an obstructive event and I was clearly awake.

Any comments on this finding?

fog.apnea wrote:There are couple instances that I could clearly see breathing (can clearly see chest movement) even though obstructive event was recorded.

Pugsy wrote:These machines don't have anyway to evaluate sleep status. They don't know if you are asleep or awake.
They only measure air flow.
Our awake breathing is actually fairly irregular when compared to asleep breathing and sometimes the air flow irregularities while awake can cause the machine to think the irregularity is some sort of apnea event. This is quite common and we call it SWJ or Sleep/Wake/Junk.
While awake we pause our breathing all the time and don't even realize we are doing....like sometimes we hold our breath when changing position in bed.

The machine will sometimes mistakeningly flag these awake breathing irregularities...not much we can do about it but shrug our shoulders and move on. Sometimes it's really obvious when there are flags right during a known awake time. Sometimes not so obvious.
People who have insomnia issues will often see a lot of SWJ flags due to repeatedly moving, tossing and turn, sighing...whatever.

It's just one of the limitations of the machine and we deal with. When I have it happen to me I just mentally remove those SWJ events from my evaluation of the therapy. For me my AHI is usually low anyway and even if they were real it's not that big of a deal.

Also sometimes you will see an OA flag but maybe the flow rate isn't totally flat...to meet the OA definition criteria the reduction in flow rate has to be at least 80% and last 10 seconds or more. So a person doesn't necessarily have to have no air moving at all...they can have as much as 20% movement and still get an OA flag.

palerider wrote:

fog.apnea wrote:There are couple instances that I could clearly see breathing (can clearly see chest movement) even though obstructive event was recorded.

You see breathing EFFORT, but if the machine doesn't show air flow, then.... well, that's the *DEFINITION* of an obstructive apnea.

TedVPAP wrote:
What are you looking at when you say that the event flag "are pretty much while turning and rolling", and "I could clearly see breathing"? Please share the data.
SH 'Events Flag' graph in conjunction with IP camera video recording.
Just to note the xpap device, IP camera and computer system are all time synced down to the second.

Also review the definition of event (help menu in sleepyhead or in your equipment manual) as apnea events are a reduction in breathing, not zero breathing.
OK

xxyzx wrote:

fog.apnea wrote:anyone know of any device/attachment (or other suggestion) to monitor/detect actual breathing (chest movement)? When I did my home sleep study, as part of the kit provided by the sleep doc office it had an attachment (guess some sort of electrode) that needed to be glued right below and near where the collar bone, chest and neck intersect.

the IHT has little tubes in the nose to do it to measure air flow
the xpap does the same thing to measure air flow

the IHT uses the belt to monitor breathing effort / chest movement
the xpap does not do that channel directly
it tells by the air flow
and if there is no air flow and it thinks the airway is open it assumes CA with no breathing effort

Julie wrote:What are you trying to assess, why?

xxyzx wrote:

fog.apnea wrote:anyone know of any device/attachment (or other suggestion) to monitor/detect actual breathing (chest movement)? When I did my home sleep study, as part of the kit provided by the sleep doc office it had an attachment (guess some sort of electrode) that needed to be glued right below and near where the collar bone, chest and neck intersect.

the IHT has little tubes in the nose to do it to measure air flow
the xpap does the same thing to measure air flow

the IHT uses the belt to monitor breathing effort / chest movement
the xpap does not do that channel directly
it tells by the air flow
and if there is no air flow and it thinks the airway is open it assumes CA with no breathing effort