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VS snores are recorded ONLY when a Philips Respironics machine is running in Auto mode. If the machine is set to straight CPAP (or straight BiPAP), the machine will NOT record VS snores. If the machine is a model number 450/460 (System One PRO) or 650/660 (System One BiPAP PRO), the machine will NOT record VS snores.
The VS snores have ''time stamps'' attached to them, but they do not have a "magnitude" number. In the OSCAR "events" list, when you look at the detailed information for each VS snore event, the number in parenthesis will always be a 0. ''But VS snores are the snores that cause the Auto algorithm to respond by increasing the pressure.'' (On a BiPAP Auto, it's the EPAP that is increased.) For each VS scored, the machine typically increases the pressure by 1 cm. Hence if there's a cluster of VS's, the machine will keep increasing the pressure until either the snoring stops or the max pressure setting is reached. It's also worth noting that in all the data we've seen, in dense clusters of VS snores, the VS snores appear to be scored in roughly one minute intervals---in other words, there is usually a full minute between adjacent VS snores.
In Encore, the VS's do NOT seem to show up as tick marks in the Events table. But it's hard to say for sure. Where they do show up is on the wave form when you look at it in Encore Pro (or EncoreBasic). Of course, Encore only downloads the wave form for the last night (or sometimes the last two nights) when you down load the data. Encore Pro at least stores all the previously downloaded wave forms in the patient's database, but EncoreBasic only stores the last wave form. OSCAR also puts tick marks for VS snores on the wave form data when a Philips Respironics machine is running in Auto and the VS data is being recorded.
So as far as we can tellbe determined: The VS snores make up the part of the snoring data that is used by the Auto-algorithm when it determines that the snoring is significant enough to warrant an pressure increase. But no one (except the Philips Respironics engineers) know what the scoring criteria for a VS snore actually is.
'''''VS2 snores'''''
VS2 snores are recorded by all Philips Respironics machines. They have both a time stamp and a "magnitude" number attached to them. In the OSCAR list, when you look at the detailed information for each VS snore event, there will be a NON-zero number in the in parenthesis for that event. Whether that number represents ''the length the snoring went on or some kind of measure of the loudness of the snoring'' is anybody's guess. We really do not know the The significance of that numberis not known.
OSCAR's VS2 graph uses the "magnitude" numbers for the vertical-coordinates in the Snore graph. In other words, the OSCAR VS2 graph is set up with the assumption that the "magnitude" numbers are somehow related to how bad the snoring is. That's not a totally unreasonable assumption since you can have VS2 events closely space together with some rather large "magnitude" numbers. But it is an assumption and there's no real way to verify whether this assumption is valid. That's why the units on the Snore graphs are labelled as "Unknown" when you hover the mouse over the vertical scale of the Snore graph.
'''Snoring Data in Encore, (the official software for Philips Respironics machines)'''
Encore calculates the VSI shown on the right sidebar of the Encore Daily Detailed data in a really bizarre way. We This can illustrate this be illustrateed with data from our the sample patient's data. On July 31, 2013, she had 3 VS 2 snores scored for the entire night. In OSCAR, the data looks like this:
<br /><br />
But it's obvious that 3/5.53 is NOT equal to 1.1 and 4/5.53 is NOT equal to 1.1. Hence Encore is not computing its VSI by simply dividing the number of VS2 snores recorded during the night by the time the machine was running. Nor is it dividing the total number of snores recorded during the night by the time the machine was running.
Instead, with a bit of mathematical reverse-engineering, we it can figure out be figured that Encore computes the Encore VSI for the night as follows:
: Encore VSI = 1.1 = 6/5.53 - (2 + 3 + 1)/5.53 = (Sum of the "magnitude" numbers of the VS #2)/(run time)
And we've checked this "formula" checked out on many other nights-- some with rather large numbers of snores and some with small numbers. It always seems to be the case that:
: ''Encore VSI = (Sum of the "magnitude" numbers for the VS 2's as shown in OSCAR)/(run time for the night)''
Why would Encore define the VSI (Vibratory Snore Index) in this way? We have no ideaIt is not known. Mathematically it makes no sense. If the snores are being scored as "discrete" events (the same way the Flow Limitations are scored as "discrete events") then the intuitive meaning of VSI would be the average number of events per hour, and VSI ought to be (number of snores)/(run time)
So that then leads to the following speculation: Is it possible that the "magnitude" number on the VS2 snores represents something ''other than '''loudness (severity)''' of the snoring''? Perhaps the "magnitude number represents the length of time measured in (seconds? minutes? number of breaths?) that snoring was being detected? In that case, the Encore VSI would then represent the average amount of "snoring time" in each hour of sleep measured in (seconds? minutes? number of breaths?)
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