Changes

ResMed S9s, PR Sysem System One PAP, CPAP and DeVilbiss IntelliPAP machines record snoring data. F&P Icons do not record snoring data.

PAP CPAP machines do not have microphones attached to them. So your PAP CPAP is not listening to the sound of your snoring. So how does it actually detect snoring? It analyzes the Flow Rate data.

When a person is snoring (at least when they're snoring loudly or persistently) there are some characteristic changes to the flow rate, and a full efficacy data PAPCPAP's flow rate analysis algorithms can pick that up. Typical types of flow rate curves exhibiting sleep disordered breathing problems can look like any of the following images:

Snoring triggers oscillations in the flow rate curve. The larger and more persistent the oscillations, the worse (and louder) the snoring is. And that pattern of oscillations is what your PAP CPAP uses to detect snoring.

The Snore graphs in ResScan and SleepyHead look pretty much the same, except for how the vertical axis is labeledlabelled. In ResScan there is a cryptic icon scale that implies that the higher the snore graph, the louder the snoring. Notice that if the snoring is really severe it may go off the top of the ResScan graph.

While it is important to remember that the S9 has no direct way of determining the loudness of the snoring, it's also clear from the ResScan graph's labels that snoring numbers above 3 represent more serious snoring than snoring numbers under 1. My guess is that Somehow the S9 decides "how loud" the snoring is and assigns the snoring number based on both the amplitude and frequency of the oscillations in the flow rate curve.

Snoring on an IntelliPAP is recorded as a graph with respect to time in Sleepy HeadSleepyHead. But the graph is a "square wave" graph rather than a curve. Here's a picture of a typical IntelliPAP Snore graph from SleepyHead:

'''Please note the following:''' The way snores are recorded on the ResMed S9 machines is very different than the way it is recorded on the PR System One machines. This post information applies only applies to the snore data recorded by the PR System One machines and how that data is reported in both Sleepy Head the SleepyHead and in Encoresoftware packages.

There's no official guide to how to interpret the Snoring information from the PR System One as it is reported in either SleepyHead or Encore. In looking at Encore numbers, the assumption is that the higher the so-called "VSI" number is, the more serious the snoring is. But exactly how large that number needs to be before it's troublesome is not known. And for reporting snoring in SleepyHead, JediMark had to back reverse-engineer the snoring data from the PR machines and the information on why Encore presents the snoring data the way it chooses to present it is pretty scarce ....

And when you start analyzing the ''raw snoring data'' the decisions that Encore makes on how to ''present '' the snoring data just seem plain seems bizarre from a statistical point of view. (More on that later.)

Once JediMark started back reverse-engineering the snoring data, he discovered that the PR machines were keeping track of two kinds of snoring data; JediMark has chosen to call these two types of snore data ''Vibratory Snores (VS)'' and ''Vibratory Snores #2 (VS2)''. Those of us who had access to Encore Pro and had data from both straight pressure mode and auto mode were able to help JediMark figure out just what the significance of those two kinds of snores are in the Encore/PR world are. Here's the run down as we now understand things:<br />

The VS snores have ''time stamps'' attached to them, but they do not have a "magnitude" number. In the Sleepy Head "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 Iwe'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 Encore BasicEncoreBasic). 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 Encore Basic EncoreBasic only stores the last wave form. SleepyHead also puts tick marks for VS snores on the wave form data when a PR machine is running in Auto and the VS data is being recorded.

So---as near far as anybody I know who follows such things we can tell: 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 nobody outside of no one (except the PR engineers ) know what the scoring criteria for a VS snore actually is.

VS2 snores are recorded by all PR machines. They have both a time stamp and a "magnitude" number attached to them. In the Sleepy Head SleepyHead 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 significance of that number.

JediMark's SleepyHead VS2 graph uses the "magnitude" numbers for the vertical-coordinates in the Snore graph. In other words, JediMark has set the SH SleepyHead VS2 graph 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 labeled labelled as "Unknown" when you hover the mouse over the vertical scale of the Snore graph.

In pre-0.9.5 versions of SleepyHead, the SleepyHead VSI index used '''VS snores''' to compute the VSI.'' If you are using a PR machine in '''''fixed pressure''''' mode and SleepyHead 0.9.3 (or earlier), SH SleepyHead will report a VSI = 0.0 even if you are snoring your head off!

'''Snoring Data in Encore, (the official software for PR machines)'''

Encore calculates the VSI shown on the right sidebar of the Encore Daily Detailed data in a really bizarre way. I We can illustrate this with data from my own our sample patient's data. On July 31, 2013, I she had 3 VS 2 snores scored for the entire night. In SleepyHead, the data looks like this:

Instead, with a bit of mathematical backwards reverse-engineering, we can figure out that Encore computes the Encore VSI for the night as follows:

And Iwe've checked this "formula" out on many other nights--- some with rather large numbers of snores and some with small numbers. And it It always seems to be the case that:

Why would Encore define the VSI (Vibratory Snore Index) in this way? I We have no idea. 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)