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→Snoring Data
It's clear from reading informational material aimed at clinicians, that each manufacturer believes that they have the "best" algorithm. But what little information that has been published about independent bench trials seems to indicate that while real differences in the auto algorithms can be quantified, the clinical significance of those differences is much harder to evaluate. This may be one reason that some sleep docs are so reluctant to prescribe APAP therapy as the first course of treatment for ordinary OSA.
= Snoring Data = Resmed S9s, PR Sysem One PAP, and DeVilbass Intellipap machines record snoring data. F&P Icons do not record snoring data. '''How does a PAP machine detect snoring?''' PAP machines do not have microphones attached to them. So your PAP 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 PAP'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:<br />[[File:flow_limitation_images_zpsdb148d1f.jpg]]<br /> 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 uses to detect snoring. Notice, too, that inspiratory snoring (snoring only on inhalations) has a different wave flow than expiratory snoring (snoring only on exhalations). It's also possible to snore on both the inhalations and the exhalations; in that case the oscillations appear on both the inhalation and exhalation parts of the flow rate curve. '''Snoring data on a Resmed S9''' Snoring data on a Resmed S9 is recorded as a function of time. At each time t, the machine assigns a "snore" number; SleepyHead graphs those "snore numbers." Here is the same Snore graph of the same 30 minutes of sleep displayed in both ResScan and SleepyHead. ResScan's snore graph:<br />[[File:snore-graph-ResScan_zpsfabebf0a.jpg]]<br /> SleepyHead's snore graph:<br />[[File:snore-graph-sleepyhead_zpsa57203b2.jpg]]<br /> The Snore graphs in ResScan and SleepyHead look pretty much the same, except for how the vertical axis is labeled. 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. On SleepyHead, the ''y''-axis is scaled from 0.0 to 5.0, with : 0.0 corresponding to the "no snoring" icon on the ResScan graph: 1.5 corresponding to the "medium/moderately loud snoring" icon on the ResScan graph: 3.0 corresponding to "loud snoring" icon on the ResScan graph. Typically anything that's over 3.0 on the SleepyHead graph has gone off the top of the scale in 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 the S9 decides "how loud" the snoring and assigns the snoring number based on both the amplitude and frequency of the oscillations in the flow rate curve. '''Note:''' The S9 AutoSet and S9 VPAP Auto will react pretty aggressively to snoring. It is not uncommon to see substantial increases in pressure in response to snoring even if no OAs or Hs are being recorded. '''Snoring data on a DeVilbass Intellipap''' Snoring on an Intellipap is recorded as a graph with respect to time in Sleepy Head. But the graph is a "square wave" graph rather than a curve. Here's a picture of a typical Intellipap Snore graph from SleepyHead:<br />[[File:Snore-Intellipap_zps90834ece.png]]<br /> The meaning of the numbers on the vertical axis is unknown, but they are presumed to indicate loudness. I've seen Intellipap Snore graphs with Snore numbers as high as 30. SleepyHead presents the snoring data very differently than the [http://www.devilbisshealthcare.com/files/IntelliPAP%20AutoAdjust%20Clinical%20Overview_LT-2089.pdf DeVilbass software]. In DeVilbass's software package, the snore data is presented as "fat" tick marks on the DeVilbass software's event table, which is shown below:<br />[[File:DevilbassSnoreData_zps2368d11e.png]]<br /> Each fat tick mark represents a ten minute time slot with at least 3 snores scored during that time period. Tick marks run together if there is snoring in consecutive 10 minute blocks. '''Snoring data on a PR System One''' '''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 only applies to the snore data recorded by the PR System One machines and how that data is reported in both Sleepy Head and in Encore. '''''All about Snoring Data on the PR System One Machines''''' 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 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 bizarre from a statistical point of view. (More on that later.) Once JediMark started back 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 /> '''''VS snores''''' VS snores are recorded ONLY when a PR 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 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 I'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 Basic). 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 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 as anybody I know who follows such things 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 the PR engineers know what the scoring criteria for a VS snore actually is. '''''VS2 snores''''' 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 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 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 as "Unknown" when you hover the mouse over the vertical scale of the Snore graph. The VS2 snores show up in Encore (all versions) as tick marks in the Events table based on the time stamp of the VS2 event. But the calculation of the VSI index in Encore is not as straightforward as you would expect. No one outside of PR really knows the difference between the changes in flow rate that are needed to score a VS and the changes needed to score a VS2. But some of the PR System One machines can be pretty sensitive to picking up vibrations that are coming from sources other than the patient's own airflow. But that said, real snoring is picked up by the PR System One as well as false snoring. You basically have to look at patterns in your own data and learn to interpret based on what you know is going on at night and what you think might be going on at night.
= Flow Limitations =
= Fancy Stuff: Other Data Available from SleepyHead =
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