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Determining moment of waking up

From our measurements we got information about respiration during your sleep. Out of this information, we get a global line of of your sleepphase throughout the night. Out of these line, we have to determine what's the best moment to wake someone between a given interval. The best moment to wake someone is just after the REM-sleep. So this is the first or second nREM-sleep stage. (see literature, add reference).

In our algorithm we have developed two methods which can determine at which moment the app should wake you. The first method is looking at the slope of the line. During REM-sleep, the respiration frequency is at its highest. So we can detect the end of the REM-phase with a drop in frequency. Another method is looking at the current frequency relative to the mean frequency of the night. With this method, we can detect a 'good' moment, i.e. when the frequency is below the mean of the past night. But the mean is probably too low, so we have to increase the value with a small factor of the variation.

However, during the REM-sleep, the respiration frequency varies a lot (see literature, add reference), so we need to be sure that a decline, or a value below the mean, is really the end of the REM-sleep and not just a variation during the REM-sleep. This can be done by looking for two or three consecutive decreasing frames. (two/three frames is around 8/12 minutes).

In the coming days, we will test both methods before we choose the best one. Another option is to combine the two methods. So we could call it a good moment of waking up when the line is declining and below the frequency threshold.

For the complete matlab-script and more information about the output-form look at the Experiments page.