For most people getting the secretions out is harder than than breathing in to get things started per se, so that generally means that the exhale pressure should be "higher" than the inhale pressure, e.g. 10-20 more. So AZGirl, if things are good, no need to tinker, but I would drop your inhalation pressure as the first tinkering step, which should give you some direction.
So for example the "insufflation pressure" (a positive number) might be 10-20 with the "exsufflation" pressure more negative than the first pressure is positive, say that 35 that yours is at, and also for PALS it may work best when part lasts 2-3x longer than the inhale part. But the sound/productivity of the cough is your best guide.
So for some other people, they might not be getting enough out because they are not getting a good enough head of steam to start with (the hypothesis I was suggesting Vikman test), so if they feel that there just isn't enough mucus being accessed, they might want to try increasing the positive pressure first and either leaving the exhale as it is, or increasing that, too. But if that doesn't work, then you want to increase the exhalation only, because that is typically "higher."
With the CA, it is important to start slow (when trying to create the best settings, I'd start at 10 on both sides of the fence) and go up on one setting at a time.
Note: there is disagreement on this topic, so if you were given different advice, I can only say the proof is in the cough.
