One of the primary factors for effective secretion clearance is the ratio of peak expiratory flow rate (PEF) to peak inspiratory flow rate (PIF). The primary purpose of this study is to examine what effect various inspiratory times have on expiratory flow bias and the PEF/PIF ratio produced by three oscillating PEP devices during simulated breathing.The secondary purpose is to evaluate any differences in flow amplitude, mean expiratory pressure, and the absolute value of peak expiratory flow between the three devices. The primary hypothesis is that as inspiratory time is prolonged, it will cause an increase in the PEF/PIF ratio and therefore improve expiratory flow bias. The secondary hypothesis is that there will be no differences in the PEF/PIF ratio, flow amplitude, mean expiratory pressure, and the absolute value of peak expiratory flow between the three devices.

The primary purpose of this study is to analyze maximum expiratory flow during OPEP therapy by comparing flow-volume loops generated by the vPEP™ and competitive devices, during simulated, spontaneous breathing. Frequency, mean expiratory pressure, maximum inspiratory flow, mean pressure amplitude, and mean flow amplitude were also measured. The hypothesis for this evaluation is that the three devices will produce similar values at five different volumes.