**R? program, sliding windows and OSCAR's FR zero-axis**

In relation to that question and my aim to determine the areas between the FR curve and its zero axis, I ask the following (dumb?) question: How does OSCAR determine the location for the zero axis for the Flow Rate (FR) graphs? Maybe it looks at balancing the scatter (using least squares?) above and below a line through the y=0=FR accidentals that do occur. Just curious.

In working on a couple of simple FL vs FR examples, I wanted the zero flow coordinates (abscissas and ordinates) in the BRP-edf file to be handy for easy numerical integration of FR data curve's "t" and "y>0" coordinates--at least for all of those time-values within brief neighborhoods up to and including an FL event.

Having to prorate/interpolate to find the zero-point values at changes of y-value signs was a pain. I did it slowly with two childishly simple (brute force) formulas, having forgotten what little I once knew about Excel VBA and macros. Even stumbling for a time, stumbling with "+" and "-" signs longer than I care to admit, to write a simple formula to interpolate for coordinate values between opposite signs.

I have been groping, along with others (see sheepless's recent thread on FL) to gain a clearer understanding of what a Resmed flow limit (FL) flag means, in mathematical and airflow terms, as those flags are presented by OSCAR from VAuto and AirSense Autoset devices.

Please help with any constructive comment or criticisms you have on approaching either the topic or my comments about the matter, the latter here and elsewhere.

A couple more after-thought but important details I'd like to know:

Does Resmed use a certain number of inspiratory waves--how many?--or use a fixed time duration--how long?--for the width of its sliding window sampling for FL effects. The larger of my two little naive tests was for a fixed time, just to get a feel for all that is involved. Only one of those tests had a meaningful result: a lone M-tipped inspiratory flow delivered 11% less air than each of its almost uniformly normal, near-neighbor, preceding breaths. This test was an instance of a wide window with just one anomalous inspiratory curve profile to evaluate.

Thank you for looking at this,

2SB

Of my 3 once-needed, helpful, and adjunctive devices I have listed, only the accelerometer remains operative (but now idle). My second CMS50I died, too, of old age and the so-so Dreem 2 needs head-positioning band repair--if, indeed, Dreem even supports use of it now.