Performance analysis of the Flutter VRP1 under different flows and angles.

BACKGROUND The Flutter VRP1 device is used for airway clearance. Its performance is based on 4 basic effects: positive expiratory pressure (PEP), forced exhalations (huff), high-frequency airway flow oscillation, and modification of mucus viscoelasticity. The purpose of this study was to determine the flow and angle conditions in which these effects are optimized. METHODS In an experimental setting, a Flutter VRP1 was fixed at angles of -30 degrees , -15 degrees , 0 degrees , +15 degrees , and +30 degrees , and submitted to flows ranging from 0.2 L/s to 2.0 L/s. The flows and angles that resulted in higher and lower values of mean pressure, mean flow, oscillation frequency, and flow amplitude were determined. In addition, it was defined which angles facilitated achieving "ideal" mean pressure of 10 cm H2O and 20 cm H2O and oscillation frequency of 12 Hz. RESULTS At all flows, +15 degrees produced higher mean pressure (p < 0.01), whereas lower values were produced at -30 degrees at lower flows, 0 degrees at intermediate flows, and +30 degrees at higher flows (p < 0.01). Higher oscillation frequencies were produced at +30 degrees and +15 degrees (p < 0.01), and lower values were produced at -30 degrees and -15 degrees at all flows (p < 0.01). Higher flow-amplitude values were produced at +30 degrees , +15 degrees , and 0 degrees (p < 0.01), and lower values were produced at -30 degrees and -15 degrees (p < 0.01). Mean pressure of 10 cm H2O was reached with the lowest flow (0.2 L/s) at +30 degrees , and mean pressure of 20 cm H2O was produced at +15 degrees (1.0 L/s), whereas an oscillation frequency of 12 Hz was reached at 0 degrees , +30 degrees , and +15 degrees , at 0.2 L/s. CONCLUSIONS Positive inclinations optimize positive expiratory pressure and flow-amplitude effects, whereas negative inclinations optimize huff effect. This theoretical knowledge may help optimize the use of the device when applied to different conditions.