Background: Metaneb® (Comedica, Inc., Dallas, TX) utilizes a fixed-venturi flow interrupter to deliver Continuous High Frequency Oscillation (CHFO) similar to that of Intrapulmonary Percussive Ventilation® (IPV) (Percussionaire Corporation, Sandpoint, ID) and Percussive-Neb® (Vortran, Sacramento, CA). Metaneb consists of a control unit, and a single-patient use "handset". The control unit operates off standard 50 psig gas (Oxygen), and contains the necessary pneumatics to deliver a fixed rate of 200-230 cycles per minute. The handset consists of the fixed venturi orifice, a nebulizer port, drive lines, and a manometer. While IPV has been utilized as both stand-alone and in-line therapy, no studies exist to determine the effectiveness of Metaneb applied as in-line therapy. The purpose of this study was to determine whether in-line application was appropriate and/or feasible.

Methods: In vitro study utilizing a standard Metaneb device attached in-line via valved tee adaptor (Cardinal #002061) to a Viasys Avea® ventilator. An intubated (7.0mm ID Oral ETT) mannequin was utilized as the test lung to allow for measurements of changes in airway pressure and flow, as well as to allow for observation of chest "wiggle" factor ( CWF - a recognized method for assessing effectiveness of CHFO). The device was tested in Volume Control (VC), Pressure-Regulated Volume Control (PRVC), Pressure-Controlled (PCV), and Airway Pressure Release Ventilation (APRV).

Results: Metaneb was successful in generating both observed "wiggle" and significant changes in flow/pressure as observed by graphics on the Avea ventilator. The greatest flow/pressure change noted was in PCV, followed closely by PRVC. Waveform changes and "wiggle" were also noted in VCV and APRV. In all cases, Peak Inspiratory Pressure (PIP) Alarms were not activated when set at 50cmH20, and measured changes in airway pressure did not exceed 30 cmH20 in any mode of ventilation.

Conclusion: Metaneb appears to be capable of being safely utilized as an in-line form of CHFO, with a waveform that is similar to that of other currently marketed devices. Further study is recommended to determine the overall efficacy of these techniques.