The Science Journal of the American Association for Respiratory Care

2008 OPEN FORUM Abstracts


Mitchell Goldstein1, Michael Terry1, Kate Gattuso1, Sunhwa Kim1, T Allen Merritt1, Elba Fayard1, Ricardo Peverini1

Introduction: The use of high frequency ventilation has become a mainline therapy in the NICU. In certain situations, electrical demand, lack of physical space, and/or large flow requirements have precluded the use of the more traditional high frequency ventilators. Our aim was to validate the potential use of a small form pneumatic HFV in applications where the traditional resources of an NICU are not readily available.

Methods: Large and small bore prototype "pocket" HFV units (Neotech, Valencia, CA) of circumference 9 and 16.5 cm respectively were connected to an open ETT interface. Flow was increased until a consistent waveform could be identified. (Mallinckrodt, St. Louis, MO). Flow and pressure data were sampled at 2000 Hz to a PC with a Validyne (Northridge, CA) UPC 2100 PCI card running Easy Sense for MS Windows. A Sensormedics 3100A High Frequency Oscillator waveform at 10 Hz, 10 LPM, PAW 18 cm, IT 33%, Amp 37 cm was analyzed for comparison. Data was plotted using MS Excel 2003.

Results: Peak oscillatory characteristics were identified at 4 lpm, with periodic peak to peak oscillation at 17 Hz using the large bore device; and 21 Hz, for the small bore device. For the large bore unit, Pressure waveform characteristics were simplified, largely positive in deflection, and diminished in amplitude compared to the 3100A; the small bore unit demonstrated more complexity and enhanced negative deflection.

Discussion: Small form factor devices tuned to a specific frequency may be of value where larger more complex oscillators are not practical. Although the frequency range of the device is outside the range of the current HFV, traditional devices (e.g., Emerson Oscillator, JH Emerson, Cambridge, MA) have ranged to 20 Hz. In transport and in developing nations, a simplified HFV may be desirable. Although the amplitude appears dampened compared to 3100A, these studies were performed on an open interface (i.e., PEEP = 0 cm). Varying PEEP loads will influence the operator frequency as well as amplitude response. Despite the fact that both frequency and amplitude were flow dependent and inseparable, it is not inconceivable that a series of "pocket" oscillators of different volume could provide for most clinical applications.

Conclusion: Small Form pneumatic HFVs can deliver waveform characteristics that are comparable to conventional oscillators and may be prove useful in applications where use of a conventional oscillator would be impractical.