BACKGROUND: Secretion removal is a key issue in patients with respiratory diseases, and is known to be most effective at vibration frequencies of ϳ13 Hz and with the greatest amplitudes possible. The Acapella devices and the water bottle are used for secretion removal in daily clinical practice but without detailed knowledge on optimal settings. The aim of this study was to evaluate the 3 different Acapella devices and the water bottle at various settings and flows to determine the optimal devices and settings for effective secretion removal. METHODS: Three different Acapella devices were tested at flows of 6, 12, 20, 30, 40, and 50 L/min, and at all 5 settings. The water bottle was filled with 5, 10, or 15 cm of water, and tested at flows of 3, 6, 10, 12, and 20 L/min. For all devices and combinations of settings, we measured the frequency and amplitude of the vibrations, as well as the required pressure to generate vibrations. RESULTS: Setting 4 was the best for all 3 Acapella devices, and the filling height of the water bottle should be 5 cm. At these settings, all devices elicited vibration frequencies between 12 and 15 Hz, which is theoretically optimal for secretion mobilization. The resistance pressures of the devices to elicit these vibrations were between 5 and 11 cm H 2 O. However, the Acapella devices elicit higher vibration amplitudes (5-8 cm H 2 O) than the water bottle (1.8 cm H 2 O) CONCLUSIONS: Setting 4 was optimal for all 3 Acapella devices. The Acapella devices may be more efficient for secretion mobilization than the water bottle, because they elicit greater amplitude of vibrations.

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