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Vibratory snore index of 242! How does Philips Calculate VS and VS2?
I'm using a Philips Dreamstation.
The brilliant Oscar software shows a huge number of VS events and the machine runs mostly at maximum pressure (14cmH20) which I presume is its response to these events.
(See attached screenshot.)
EncorePro states a typical weekly Average VS Index of 156 (and on one night a figure of 242!)
It seems to me that either there's something very odd happening with my breathing or the machine has a fault.
Has anyone here seen anything similar?
Thanks.
The Philips Respironics machines report VS and VS2. We're a bit unsure how VS2 is detected, but we often recommend that users just turn off that event. VS seems to to be a reasonable approximation of actual snoring events and is detected as a vibration in the machine's flow sensor. Looking closely at the flow rate graph wave-form, we can often visualize a vibration at the peak of inspiration that is a good affirmation that a snore occurred. The Philips Respironics auto CPAP and BiPAP react to detected VS with pressure increases. VS2 on the other hand can be tied to the tube moving over the bed or bedside table, a snoring dog and random noises, and the machines do not react to this channel.
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In my experience when I used the Dreamstation, VS2 was chasing ghosts. I say that because I always had a high VS2 count every night. Being curious I started video recording my self while sleeping and found that I was sound asleep, not moving, breathing normally and the Dreamstation still recorded VS2. Combined with my snore detector (wife) who tells me I don't snore since using CPAP, I don't take VS2 readings seriously. I just turned it off on OSCAR and ignored it.
For reference, what OSCAR calls "VS2" shows up on official reports as flagged "VS" regions in the overview only. In contrast, "VS" (as OSCAR uses the term) is what gets flagged on official waveform reports only.
They are reported separately by the machine, but since OSCAR doesn't have any way to call them both VS and to treat them differently, they both show up in both places, along with the number per hour on the left hand summary.
(12-05-2021, 10:19 AM)Sleeprider Wrote: The Philips Respironics machines report VS and VS2. We're a bit unsure how VS2 is detected, but we often recommend that users just turn off that event. VS seems to to be a reasonable approximation of actual snoring events and is detected as a vibration in the machine's flow sensor. Looking closely at the flow rate graph wave-form, we can often visualize a vibration at the peak of inspiration that is a good affirmation that a snore occurred. The Philips Respironics auto CPAP and BiPAP react to detected VS with pressure increases. VS2 on the other hand can be tied to the tube moving over the bed or bedside table, a snoring dog and random noises, and the machines do not react to this channel.
Your VS index is high, and it might be worth posting the full Daily detail report from your Oscar data.
Thanks VERY much for that.
I need to take some time reading the wiki, there's lots of useful stuff there.
But one thing strikes me as strange...
As I understand it the Respironics algorithm only reacts to VS events and not VS2 events (and that's what I'm seeing on my Oscar reports).
However the wiki says: Encore VSI = (Sum of the "magnitude" numbers for the VS 2's as shown in OSCAR)/(run time for the night) Is that correct?
Machine: Dreamstation Auto SV Mask Type: Full face mask Mask Make & Model: Phillips Dreamwear Humidifier: Built in Humidair Auto CPAP Pressure: 4 to 16 CPAP Software: OSCAR
DreamMapper
Other Comments: I am not a MD and my advice should be taken with a pinch of salt and plenty of water
I thought my VS2 numbers were high until I saw yours and I know for a fact that I do not snore or I wouldn't hear the end of it from my wife.
Unlike Resmed and other makers, Dreamstation Respironics line use an enormous number of sensors that their software monitors, one being the vibrations in the tube (as other posters have already indicated) . The software cannot discern between physical snoring that sets off this sensor or other causes of vibration (can be too much tossing and turning or leaks)...Looking at large leaks in your data, it stands just below 4% and I bet if you can reduce these leaks, your VS2 numbers would drop too but you most likely won't be able to bring it down to zero as this sensor is particularly sensitive.
I'll be following this thread to see how you progress.
I've read that the VS flags can drop in response to the hose rubbing on something (bedding, e.g.). You could put the hose in a hose cover to see whether that changed anything. Also, you can try recording yourself during the night just to make sure you're not actually snoring this much (but I bet you aren't).
