This is a literature review summary of "Airway Clearance Therapy (ACT) non-pharmacological) Clinical Trials," in no particular order.  Most of these were found at clinicaltrials.gov.  Most results were found on pubmed.com.  There are relevant links for each study below their respective summary.

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One study in particular is of interest:  NCT00817180   Multi-centre, Long-term Comparative Trial of High Frequency Chest Wall Oscillation Versus Positive Expiratory Pressure Mask in the Treatment of Cystic Fibrosis.  In our opinion it is one of the better studies, and there is an excellent editorial by Dr. Eleanor Main discussing outcome measures related to this study which may be found at: https://thorax.bmj.com/content/68/8/701.full  

Vibralung's efficacy study (Study II) had 11 in-patients complete the 11 day study, divided into 2 five day periods with a one day washout. In reviewing other airway clearance device studies, there is a wide variance in both N patient numbers and length of patient treatment. (The N number of patients was taken from the results of the study when found.)
NCT00717873 N=280, 10 days
NCT00817180 N=107, 1 year -- this is the best study by far.
NCT01854788 N=31, 1 week
NCT00816309 N=20, 7 months
NCT00308958 N=15, 4 days
NCT02324855 N=26, 1 year
Vibralung        N=10, 2 visits (safety)
Vibralung        N=11, 11 days (efficacy)
NCT00817947 N=9, 4 days
NCT01266473 N=6, 8 weeks
NCT03078127 N=10, 0-274 minutes

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