Pugsy wrote:Again....a Respironics software tech told me that the machine pulls a leak baseline of sorts from when the machine is started up and we would assume excess leaks are minimal and uses that to have a starting point.
Are you sure the tech was talking about an intentional leak detection function? The machine has to keep a running calculation of total leak at all times in order to make the flow rate waveform be centered around zero. Could the tech have been talking about how they start this calculation up? Long term, this is a running average of the hose flow rate, but you need to figure out how to set the initial value when you start the machine up.
If they do calculate an intentional leak, why is there no unintentional or intentional leak data recorded on the SD card? Apparently, Jedimark couldn't find it. Check this thread:
viewtopic.php?f=1&t=73250
Maybe it calculates some sort of intentional leak rate and uses it in some of its internal calculations like apnea detection, and central detection.
Pugsy wrote:Regarding Encore and unintentional leaks.....it has to pull it's computations from the machine...the machine supplies what it needs to figure it out. Encore can't make up figures without something to base the figures on. Think about it. Encore doesn't use the magic eight ball to pull a leak number out of its butt.
Once again, the only sensors the CPAP machine has is a flow rate sensor and a pressure sensor. (There's also a humidity sensor, but I doubt that figures in here.) All the data the CPAP or Encore has is calculated comes from analyzing those two sensor readings. Some of the calculations are done inside the CPAP machine, some are done in Encore.
In this thread,
viewtopic.php?f=1&t=73250, Jedimark says he talked to a PR representative who told him that Encore calculates intentional leaks from the pressure, not that it gets the data from the CPAP machine.
"I asked her how Encore calculates unintentional leaks.. She said it's calculated using set values for each pressure, regardless of mask type.. (Yay.. No voodoo magic involved!)"
Note it's Encore calculating unintentional leaks, not the CPAP machine.
I believe it works this way. The PRS1 machine calculates total leaks and records it. Encore calculates an intentional leak based on the pressure, and subtracts that from the total leak to get unintentional leak. Encore gets no information about unintentional or intentional leak rates from the machine.
In the thread linked above, it sounds like SleepyHead calculates unintentional leak by finding the minimum leak at each pressure. (actually a 10th percentile.) I don't know if he still does it that way. I know he's been tinkering with the PRS1 unintentional leak calculation for a while.