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'''The Flow Rate graph'''
'''NOTE:''' ''ResMed S9, Philips Respironics System One, and FFisher &P Paykel Icon machines record Flow Rate data if the card is in the CPAP machine during the night; the DeVilbiss IntelliPAP does NOT record Flow Rate data.''
The Flow Rate graph is also referred to as the "wave flow" graph. It provides a record of each and every breath you took all night long. At this scale, everything is all run together; the real power in the Flow Rate graph is when you zoom in sufficiently close to start seeing individual breaths and events. Note that each of the events in the event table shows up as a tick mark on the Flow Rate graph (with the exception of the Philips Respironics System One VS2 tick marks.) The little boxes appearing on the sample patient's Flow Rate graph are mostly Pressure Pulses that the Philips Respironics central detection algorithm uses for testing the patency of the airway.
'''The Flow Rate graph---a detailed look'''
'''NOTE''': ''Only ResMed S9, Philips Respironics System One, and FFisher &P Paykel Icon machines record Flow Rate data; if you are a DeVilbiss IntelliPAP, you will not have a Flow Rate graph when you look at your data in SleepyHead''
The Flow Rate graph is a visual record of each and every breath you took while using the machine. You are inhaling when the Flow Rate is positive and you are exhaling when the Flow Rate is negative. Stronger inhalations result in higher (positive) peaks and stronger exhalations result in lower (more negative) valleys in the Flow Rate graph. The events from the Event Table are superimposed on the Flow Rate graph with vertical lines of different colors.
'''Defining Large Leaks'''
Different manufacturers have different definitions of what Large Leak means for their machine. But for all brands of machines, the idea is that if your leaks are under the manufacturers Large Leak definition, the machine should be able to gracefully compensate for the leaks and deliver effective therapy and accurate data. Information about how ResMed, Philips Respironics, FFisher &P Paykel and DeVilbiss each define '''''Large Leak''''' can be found in [http://www.apneaboard.com/wiki/index.php?title=Beginner%27s_Guide_to_SleepyHead#Leaks 8. Leaks].
'''Tools to help identify Large Leaks: Show Leak RedLine'''
* ResMed S9 users will see the AHI, Obstructive Apnea Index (OAI), the Hypopnea Index (HI), and Central Apnea Index (CAI).
* DeVilbiss IntelliPAP users will see the AHI, Apnea Index (AI), NonResponding Apnea Index (NRAI), and the Hypopnea Index (HI).
* FFisher &P Paykel Icon users will see the AHI, Apnea Index (AI), and Hypopnea Index (HI).
The long term indices are computed in the same way the nightly indices are computed: SleepyHead counts the number of events recorded during the time frame for the index and divides that by the total run time for the time frame. In other words the long term indices are long term averages.
* Users of DeVilbiss IntelliPAP CPAP/APAPs, FFisher &P Paykel Icon CPAP/APAPs, and Philips Respironics System One CPAP/APAPs will have Pressure data.
* Bi-level users will have IPAP/EPAP data regardless of the brand of machine.
* ResMed S9 CPAP/APAP users who use EPR will have IPAP/EPAP data because these machines act very similar to bi-levels. The IPAP data is the pressure level data; the EPAP data is the pressure level - EPR setting. In other words, if the pressure is 8 and EPR = 2, the IPAP = 8 and the EPAP = 6 = 8 - 2.
* ''ResMed S9''. You should use the default Redline setting of 24 L/min, and and you want to keep the Leaks graph under this line.
* ''F Fisher & P Paykel Icon''. The FFisher &P Paykel Icon reports TOTAL leaks and the FFisher &P Paykel Icon definition for Large Leak is a TOTAL leak rate that is above 60 L/min. You should set the Redline at 60 L/min and you want to keep your TOTAL leaks under a Redline drawn at 60 L/min.
* ''Devilbiss IntelliPAP Auto''. The Devilbiss IntelliPAP reports Total leaks and the Devilbiss definition of Large Leak is a TOTAL leak rate that is above 95 L/min. You should set the Redline at 95 L/min and you want to keep your TOTAL leaks under a Redline drawn at 95 L/min.
* ''Philips Respironics System One''. The Philips Respironics machines report TOTAL leak, but Philips Respironics never tells us what the official definition of a Large Leak. SleepyHead 0.9.6 now flags the official Encore Large Leaks as gray bars over the Flow Rate graph. So if you get a lot of large leaks, you can use that data to help you decide where to draw a Large leak line. But until you get some data, here's a staring place to make some guesses about where to draw the Redline that are based on looking at a lot of Encore data from a lot of Philips Respironics users over the years:
ResMed machines record and report only the ''Excessive Leak''. The S9 takes the raw (total) leak data and the mask setting and uses that to record the ''Excessive Leak'' data. The raw Total Leak Rate data is not recorded to the SD card or the machine's internal memory.
SleepyHead uses '''''Total Leak Rate''''' to refer to the leak data recorded by Philips Respironics, FFisher &PPaykel, and DeVilbiss machines; the SleepyHead Total Leak Rate includes both the intentional leak rate and the excessive leak rate. SleepyHead uses '''''Leak Rate''''' to refer to only the excessive leak rate. It's important to remember the following things about the SleepyHead Total Leak/Leak Rate data:<br />
* ResMed users will only have ONE leak line and it is Leak Rate.
* Philips Respironics, FFisher &PPaykel, and DeVilbiss users will have TWO leak lines: One for Total Leak Rate and one for Leak Rate.* The Leak Rate for Philips Respironics, FFisher &PPaykel, and DeVilbiss users is calculated by SleepyHead from the data recorded by the machine. SleepyHead uses a statistical analysis of the Total Leak Rate data to determine an estimate for excessive leak rate and reports that estimate as Leak Rate. If you are using a bi-level device or if you are using an APAP with a wide range of pressures, it is possible that the estimated excessive leak rate may not be accurate; in that case you are better off looking at the Total Leak Rate data and using it to determine how good or bad your leaks are.
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* '''Fisher & Paykel Icon:''' When the Total Leak Rate is AT or ABOVE 60 L/min, it is a Large Leak.
(Source: [http://www.fphcare.com/CMSPages/GetFile.aspx?guid=4ce946e5-51d0-4739-8aab-d7d8727d157e F&P InfoSmart Spec Sheet])
In FFisher &PPaykel's InfoSmart software, Large Leaks are flagged by a line drawn at 60 L/min in the (total) leak graphs. DeVilbiss IntelliPAP users can use the Show Leak Redline option to draw a Red Line at 60 L/min in the Leak Rate/Total Leak Rate graph in SleepyHead 0.9.6. (Earlier versions of SleepyHead do not have this option)<br />
For ResMed users or for folks who simply want to concentrate on the (excessive) Leak data, a Good Leak line will be "fuzzy" flat, stay mostly around 0.0 L/min, but tends to have some visible periods of noticeably higher leaks, most of which stay below 10-15 L/min. A Decent Enough Leak line has more obvious leaks than a "Good" one does, but line stays below 25-30'''*''' L/min for at least 80-90% of the night. (There's some debate between CPAP users of just how long the Large Leaks need to last before they become problematic).
* ''In general patients can trust the Total Leak data and the machine manufacturer's Large Leak definition more than eye-balling the (excessive) Leak graph in SleepyHead if one is indicating there's a Large Leak and the other is not. That means that users of IntelliPAP machines may have a bit higher "Leak" number than 24-30 L/min before it really counts as a Large Leak; on the other hand users of Icons with masks that have relatively high expected leaks may have Large Leaks where the (excessive) Leak graph is quite a bit lower than 24 L/min: If the expected leak rate of your graph is 45 L/min and you use an Icon, any excess Leak that is more than 15 L/min is likely be flagged as an Large Leak in the FFisher &P Paykel software since the Total Leak will be AT or ABOVE 60 L/min, which is the Large Leak line for the Icon.''
Here's an example of a "Decent Enough" leak line from our sample patient's own data:
On an in-lab sleep test (PSG), each apnea will be classified as either an ''obstructive apnea'' or ''central apnea''. The data from the belts around the chest and abdomen are used to distinguish between the two types of apnea on a PSG. If the belts indicate that the patient is trying to breathe, but no air is getting into the lungs, then it's assumed that the problem is that the upper airway has collapsed and the apnea is scored as an ''obstructive apnea''. But if the belts indicate that the patient is making ''no effort'' to breathe, then it's assumed that the problem is that the brain has "forgotten" to send the signal to the diaphragm and lungs to inhale. The patency of the airway is irrelevant when scoring a central apnea on a PSG because the main problem is with the brain's forgetting to tell the diaphragm and lungs to breath. And it's possible for the airway to collapse during a central apnea.
But our CPAPs have no way to determine the effort to breathe. Hence CPAPs cannot distinguish between obstructive and central apneas in the same way that the technician monitoring a PSG does. Originally full efficacy data CPAPs did not try to distinguish between obstructive and central apneas. (The FFisher &P Paykel Icon still does not try to distinguish types of apneas.) But when manufacturers started designing Auto CPAPs, a potential problem had to be addressed in the Auto algorithms: A minority of CPAP users are sensitive enough to pressure to develop problems with pressure-induced central apneas. And the tendency to have problems with pressure-induced centrals is more pronounced the higher the pressure setting on the CPAP. Hence early APAP Auto algorithms often were designed to NOT increase the pressure in response to apneas scored at pressures of 10cm or greater. In an effort to get around this difficulty, many of the current generation of full efficacy CPAPs make an effort to distinguish between apneas are presumed to be obstructive and those that are presumed to have a high probability of being central, and an APAP with such a "central apnea detection" algorithm can be programmed to respond to the apneas classified as obstructive and ignore the other apneas.
ResMed and Philips Respironics CPAP machines use (different) proprietary algorithms to test the patency of the airway and use the result to classify each apnea as a ''clear airway apnea (CA)'' or an ''obstructive apnea (OA)''. When the data from the algorithm leads to an ambiguous result, the apnea may be scored as an unknown apnea (A or UA). Both ResMed and Philips Respironics Auto machines will increase the pressure in response to clusters of OAs, but they will not increase the pressure in response to apneas scored as CAs.
DeVilbiss machines use a very different algorithm to classify each apnea as an ''apnea (A)'' or a ''non-responding apnea (M or NRA)''. A DeVilbiss Auto machine will increase the pressure in response to events classified as "apneas", but it will not increase the pressure in response to "non-responding" apneas.
As near as I can tell, FFisher &P Paykel machines do not try to distinguish the type of apnea. And I have not been able to find any specific information about how the FFisher &P Paykel Icon responds to machine scored apneas.
It's also important to remember that the ResMed and Philips Respironics algorithm for distinguishing between OAs and CAs and DeVilbiss algorithm for distinguishing between As and NRAs are not infallible. They are prone to misclassifying apneas under certain circumstances. For most users, it's not a huge problem, but for a small number of users, it can be an issue. We're not familiar enough with the DeVilbiss alogrithm to have a good sense of its limitations. But both the ResMed and Philips Respironics algorithms are based on using variations in the CPAP pressure to test the patency of the upper airway. As such they both have the same broad characteristics:<br />
* '''Philips Respironics System One:''' The numbers are event markers. For CAs, OAs, Hs, PBs, and LLs, the numbers are usually a good approximation of the event length measured in seconds. For RERAs, it appears that the number is a good approximation of the event measured in seconds. For VS, VS2, and FL it is not at all clear what the meaning of the numbers is. SleepyHead uses the VS2 numbers to draw the Snore graph; presumably the higher the number attached to a VS2, the louder OR longer the snoring. It's not clear which. For more information on how the Philips Respironics scores snoring see [http://www.apneaboard.com/wiki/index.php?title=Beginner%27s_Guide_to_SleepyHead#Snoring_Data 10. Snoring Data].
* '''DeVilbiss IntelliPAP:''' The numbers in the parenthesis are usually single digit numbers and it is not clear what their meaning is. Since the IntelliPAP does not record Flow Rate data, it is impossible to see whether there is some connection between these numbers and the lengths of the events.
* '''FFisher &P Paykel Icon:''' The numbers in parenthesis seem to always be 1, and hence they are not related to the length of the event. You can zoom in on each event in the Flow Rate curve and estimate the length of the event visually.
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= Snoring Data =
ResMed S9s, Philips Respironics System One CPAP and DeVilbiss IntelliPAP machines record snoring data. FFisher &P Paykel Icons do not record snoring data.
'''How does a CPAP machine detect snoring?'''
UNDER CONSTRUCTION
'''NOTE:''' DeVilbiss machines do NOT record FL data; FFisher &P Paykel Icons do record FL data
What a FL is and how they're scored differently on ResMed and Philips Respironics.
* ''ResMed S9'' users will lose all of the detailed daily data and all of the Daily Data graphs. But summary data for the day should show up in SleepyHead 0.9.6.
* We don't know exactly what ''FFisher &P Paykel Icon'' or ''DeVilbiss'' users will lose.
== Q: How often do I need to import my data into SleepyHead? ==
* ''ResMed S9'' users need to import the data on a weekly basis if they want to see all available data, including the Flow Rate graph; the S9 overwrites the high resolution data (including the Flow Rate data) on a seven day cycle: In other words, tonight's high resolution data replaces the high resolution data from one week ago. The rest of the detailed daily data (pressure, leak, event table), is overwritten every 30 days.
* ''FFisher &P Paykel Icon'' users need to import the data on a weekly basis; the FFisher &P Paykel Icon overwrites the daily detailed data on a seven day cycle: In other words, tonight's detailed daily data replaces the high resolution data from one week ago.
* ''Philips Respironics System One'' and ''DeVilbiss IntelliPAP'' users can download much less frequently. These machines store several months to a year's worth of full efficacy data on the SD card. It's still not a bad idea to import the data into SleepyHead on regular basis in case the SD card becomes corrupted.
== Q: I don't see any Flow Rate data. What am I doing wrong? ==
A: DeVilbiss IntelliPAP users will not see any Flow Rate data because the IntelliPAP does not record that data to the card. ResMed S9, Philips Respironics System One, and FFisher &P Paykel Icon users will only see Flow Rate data if the card was in the machine while it was running; the Flow Rate data is written directly to the card. ResMed S9 and Icon users who do not down load their data at least once a week will only get the last 7 days of Flow Rate data for each down load: The S9 and the Icon both overwrite the Flow Rate data once a week.
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