@picartist Tbere seems to be a lot of misinformation about PEP devices like Aerobika. The lever controls the frequency of the oscillation, not the amount of force required to operate the device.
According to my first pulmonologist's nurse, who was of more help than anyone else except my speech therapist, the oscillation is designed for different purposes. First, deep breathing patterns, with a hold and full exhale, gets the air deep in the lings, below the mucus. Then lower frequency (slower) oscillations open the larger airways, switch to higher frequency (faster) ones move the mucus from smaller airways so you can huff cough it out. Repeat the pattern a few times.
Forceful coughing and breathing are stressful to the airways, larynx, throat and maybe even lungs. This can actually make you feel worse, and/or increase the amount of mucus.