I initiated a previous thread concerning the difference between my maximum leak rate on Rescan versus Sleepyhead. Since then I have been watching this and have found that it occurs all of the time. It is just the statistics. The graphs look identical. I have also noted that the 95% leak rate suffers from the same difference.
I have not methodically scrutinized the respective leak rate graphs for comparison but they look identical. So why the difference in statistics? I have an idea, which is what I want to present.
First the leak rate is calculated based on an offset of the exhalation curve from the expected curve. In order to provide the expectation the software uses some number of curves to set up a zero line and then compares the actual measured curves to the zero line. The offset is the unintentional leak rate.
As a result, it seems to me, that if one is breathing very regularly and then suddenly takes a deep breath that will show up as a spike in the leak rate graph. I imagine that I am simplifying this somewhat but this train of thought made me curious. I started looking at the spikes in my leak rate chart and noticed that for many of these spikes there was also simultaneously a spike in my flow chart.
I also did a small test with my CPAP. After I had awakened in the morning, I stayed in bed for an extra 20 minutes and breathed with different tidal volume and timing. At the same time, I was carefully checking for unintentional leakage all around the mask. I can usually feel leakage but I also checked for leakage using my hands. There was no leakage. When looking at my leakage graphs, there were leaks recorded through that whole 20 minutes. Not large leaks but spiky and higher than previous leakage rates. Made me feel like I was definitely on the right track
Here is what I think may be going on with the statistics. I think that Resmed recognized this and set up an algorithm that ignores these for statistical purposes. Therefore the Rescan 95% and maximum leak rate statistics are always lower than the equivalent Sleepyhead statistics. The median may suffer from the same difference but my median is always 0 which makes it a little difficult to tell.
If anyone has opinions on this situation, please bring them up.