Laboratory Evaluation of the Acapella Device: Pressure Characteristics Under Different Conditions, and a Software Tool to Optimize Its Practical Use

BACKGROUND: The Acapella is a respiratory rehabilitation device designed to aid sputum clearance. When the patient exhales through this device, continuous and oscillatory pressure levels are produced. The adequate practical use of the Acapella is critically dependent on the characteristics of the produced pressure, which include the production of a mean pressure ≥ 10 cm H₂O and a matching of the oscillation frequency with the respiratory-system resonance frequency, and/or with the frequency of ciliary movement (approximately 13 Hz). The development of a dedicated software tool would contribute to optimize the clinical application of this device. Thus, the aim of this study was 2-fold: to characterize the mechanical behavior of the Acapella, and to develop a software tool to ease the practical use of this device.

METHODS: An experimental setup was assembled in order to study mean pressure, oscillation frequency, and the oscillation amplitudes produced by 3 Acapella devices (model green) in the whole range of instrument adjustments and under air flow rates ranging from 200 mL/s to 800 mL/s. In order to increase flexibility, allowing the fast integration of further information obtained in future studies, the software was developed in a graphical environment.

RESULTS: The device characterization showed an oscillation frequency varying from 8 Hz to 21 Hz, mean pressure ranging from 3 cm H₂O to 23 cm H₂O, and oscillation amplitude from 4 cm H₂O to 9 cm H₂O. These parameters increased with flow and instrument adjustment. A user-friendly software was developed, incorporating the current knowledge concerning secretion removal. After the introduction of the desired frequency and the patient air flow by the user, the software automatically calculates the necessary instrument adjustment, as well as mean pressure and oscillation amplitude.

CONCLUSIONS: The Acapella device may produce clinically adequate values of mean pressure and oscillation frequency. However, it depends on its use at optimized conditions. The user-friendly software proposed in this study could help the user to achieve these conditions.