auto CPAP time at pressure graph - Help!

I'm getting better at analyzing the data from EncoreViewer (and SleepyHead, etc.) but still puzzled about the "Auto CPAP Time at pressure" graph given at the end of the report. I'm especially confused because the y-axis seems to have two labels: Cumulative Hours of Usage and Percent of Time.

So here's my graph for the past week:


The way I'm reading it is out of 32 hours of usage over the past week the machine spends roughly 90% of the time it's running at 14... but then when you look to the right, by that logic it looks like it would spend more than 90% of the time at 18 (the highest possible)... and that doesn't work out.

Would much appreciate if someone could shed some light on this issue for me. Also, what is the normal range for this metric? How would it look if it was something to be concerned about?

I don't have a PR system nor EncoreViewer but I'm guessing that it's 95% of the time at 18 or less. 90% of the time at 14 or less. Just a hunch. Someone here knows for sure.

soldamerican wrote:I
The way I'm reading it is out of 32 hours of usage over the past week the machine spends roughly 90% of the time it's running at 14... but then when you look to the right, by that logic it looks like it would spend more than 90% of the time at 18 (the highest possible)... and that doesn't work out.

Would much appreciate if someone could shed some light on this issue for me. Also, what is the normal range for this metric? How would it look if it was something to be concerned about?

No, you are misinterpreting the graph.

The graph crosses the 90% line right at 13cm, but just barely above 13cm. The point on the graph at (13, 90%) means that you spent 90% of your time AT or BELOW 13cm of pressure. And you spent 10% of your time AT or ABOVE 13cm of pressure. The red line at 14cm of pressure is to indicate that 14cm is the first integral cm of pressure reading AT or ABOVE the 90% and PR uses that as the 90% in these graphs. Technically it looks like 14 is about the 92%---in other words it looks like you spent about 92% of the time AT or BELOW 14cm of pressure.

Finally, since the y-values go up from 90% at 13cm of pressure to about 92% at 14 cm of pressure to about 95% at 15cm, we can conclude that you spent about 5% of the total time with pressures between 13 and 15 cm. In other words, your pressure was roughly 14cm for about 5% of the time the machine was running.

I'll also take the time to point out thatyou spent a bit over 50% of the time AT or BELOW 10cm of pressure since the graph crosses the 50% line just before hitting 10cm. So 10cm is close to your median pressure or your 50% pressure. Note that median is not the same as average.

Today's math lesson is brought to you by RobySue, the friendly math prof.

Respironics actually reports 90% numbers and Resmed reports 95% numbers.
SleepyHead actually allows for people to choose which way...I think the default seems to be 95%.
Minor difference and not a critical issue and why I don't make a big deal about it when a Respironics user reports 95% from a SleepyHead report. Besides..you all know how I feel about % numbers anyway.

Encore software reports 90% numbers..whether it is pressure or leak on the older machines.

The above graph...I have no clue what its significance is. I don't have it available in any of my Encore software reports from when I used a Respironics machine. Not with Pro, Viewer or Basic. This is the first time I have seen it.

What software generated that graph? EncoreViewer 2.0? What function generated it? I viewed all my detailed graphs as well as a summary and couldn't get that graph to show up.

Pugsy wrote: What software generated that graph? EncoreViewer 2.0? What function generated it? I viewed all my detailed graphs as well as a summary and couldn't get that graph to show up.

EncoreViewer 2.0. I just ran a report for a specific date range (the past year for this particular report) and it gives this graph on the second to the last page. The graph is for the most recent week though. If you run the report for stats of less than a week then it gives you this graph for those days.

robysue wrote:I'll also take the time to point out thatyou spent a bit over 50% of the time AT or BELOW 10cm of pressure since the graph crosses the 50% line just before hitting 10cm. So 10cm is close to your median pressure or your 50% pressure. Note that median is not the same as average.

Today's math lesson is brought to you by RobySue, the friendly math prof.

Ok, thanks, that makes sense.

So, am I good? does this seem like a normal reading?

Got it. I had to go way back to my APAP files. I don't have them in Basic or Pro because accidentally messed up SD card so I don't have them available to put into Pro but this graph I now remember.
The graph is just another visual for the table that is shown above this graph.
It is just another way of showing the 90% pressure table.
There are no "normals" nor "abnormals" for this particular graph. It is just stating the facts as it sees them.
A quick way for you to see a trend for 90% pressures. Remember all that 90% number means is that you were are OR below that number. People tend to forget the or below part. It is just a statistic sometimes useful in establishing long term trends for pressure needs.
Here is an example of mine...I did a short term one...see elevated 90% pressure? I just did a 6 month trend and the 90 % pressure was only 12.9 for 6 months... 90% numbers are easily manipulated when looking at short term data.

Where did you get the 12.9 from?

Pugsy wrote:The above graph...I have no clue what its significance is. I don't have it available in any of my Encore software reports from when I used a Respironics machine. Not with Pro, Viewer or Basic. This is the first time I have seen it.

What software generated that graph? EncoreViewer 2.0? What function generated it? I viewed all my detailed graphs as well as a summary and couldn't get that graph to show up.

The graph shows up in Encore Viewer, Pro, and Basic when I'm using Auto mode. There's no special "function" or setting to get the graph as near as I can tell. It's on the second to last page of the whole big "report" after the seven days worth of detailed overnight data when I run my data through any of the Encore products.. And all it is is a visual graphic of the pressure percentiles when running in Auto mode.

RobySue...I found it. Had to go back to APAP...I was looking in BiPap reports and I only did one night in auto mode on the BiPap.

Dori...I got the 12.9 from the last page of the Encore reports..the overall summary after changing the report viewing dates to cover 6 months of reports instead of the normal 1 week. The default is to show only the most recent 7 nights...I had to change it to show 6 months. The 5 nights that are absent.. I was away from the house and I used the M series machine and I couldn't mix machines in Pro. Overall...I have more nights with much less than that 17 cm 90% pressure number and thus why I don't put a lot of faith in 90% UNLESS they also happen to be close to average pressure OR I see it pretty close to long term reports like this one. I never put much faith in short term 90% anything...it is too easily skewed by just a couple of off nights.