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→Basic data interpretation: Overview Data
Long term trends in the efficacy data are important for many reasons. One of the most important is that we all have the occasional bad night where the AHI is much higher than normal or the leaks are awful. Occasional bad nights do not indicate that there's something wrong with the way the CPAP therapy is going. (Although a really awful night for leaks might indicate it's time to replace those nasal pillows or to check whether the mask was put together correctly). Since sleep doctors meet with many patients each month, they tend to focus almost exclusively on the long term data---a small number of well-understood summary numbers and graphs are easier to review than massive amounts of daily data.
The Overview data is a graphical representation of the highlights of the Detailed Daily data over a range of days (or months or years). Each of the graphs is either a bar graph or a line graph with one entry for each day's data. The following screen shot shows three of the more useful Overview data graphs from a sample patient:<br />
[[File:overview1_zps35d8e666.jpg]]
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The bar for each day's AHI data is split into three colors; the relative sizes of each bar reveal the relative number of events. Bars that are<br />
Looking at the data as a whole, we see that it took this patient about three weeks to really settle into CPAP and have the AHI come down to what's now his normal range. It's also interesting to note the spike in AHI on June 12. This particular patient had a bicycle accident on that day and got scrapped up pretty good, with a broken toe and a significant lacerations on his right ankle and shoulder. He was in pain that night, which is likely related to the higher AHI.
==The Usage Compliance Overview==The usage graph is often mentioned, but it can be seen from the number at the top left of the graph that the patient is averaging 6:57 hours of mask time and that he's only had two days with really significant problems keeping the mask on. (One of those nights was during an overnight driving event where the patient didn't get to bed until 7:00 a.m.; the other was another cross country drive where he got to bed around 3:00 a.m.). The user is "compliant" by using the XPAP for more than 4-hours/day for at least 21 of 30 days, or 70% of days in a month.
==Session Times Overview==
The Session Times graph give a good overview of sleep patterns. If you sleep well, this graph probably won't be of much interest. If you have problems with insomnia or circadian rhythm problems, looking at the patterns in this graph may go a long way towards explaining why you may not be feeling much better even with CPAP: CPAP fixes OSA, but it does not fix bad sleep that are caused by other things. In the patient’s Session Times data, it's easy to see that his wake up times are a bit more regular than his bedtimes. It's also easy to spot which nights he had trouble keeping the mask on.
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==Leaks and Total Leak Overview==
The Leaks and Total Leaks graphs show the maximum, 95%, and median Leaks and Total Leaks for each day. The 95% (or 90%) and median Leak graphs are are more important than the maximum values. The patient has had a few days where his 95% leak rate was pretty high, but not high enough to have had any leaks flagged as Large Leaks in his Daily Data.
==AHI Overview==
The Peak AHI graph gives graphical information about the number of apneas and hypopneas recorded in any 60 minute period during the given night's data. The Maximum Peak AHI is the maximum number of events that occurred during any one hour of the given night; this is a crude measure of how bad the worst hour of the night was. The Maximum Peak AHI values are usually going to be quite a bit higher than the overall AHI for the night because for most of use, once we start CPAPing we have long period with no events and hopefully many hours where the hourly AHI is at or close to 0.
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