Journal of Applied Physiology, Vol 66, Issue 3 1127-1135, Copyright © 1989 by American Physiological Society
Frequency and amplitude effects during high-frequency vibration ventilation in dogs
Y. Shabtai and N. Gavriely
Department of Physiology and Biophysics, Faculty of Medicine, Technion-Israel Institute of Technology, Haifa.
High-frequency external body vibration, combined with constant gas flow at
the tracheal carina, was previously shown to be an effective method of
ventilation in normal dogs. The effects of frequency (f) and amplitude of
the vibration were investigated in the present study. Eleven anesthetized
and paralyzed dogs were placed on a vibrating table (4-32 Hz). O2 was
delivered near the tracheal carina at 0.51.kg-1.min-1, while mean airway
pressure was kept at 2.4 +/- 0.9 cmH2O. Table vertical displacement (D) and
acceleration (a), esophageal (Pes), and tracheal (Ptr) peak-to-peak
pressures, and tidal volume (VT) were measured as estimates of the input
amplitude applied to the animal. Steady-state arterial PCO2 (PaCO2) and
arterial PO2 (PaO2) values were used to monitor overall gas exchange.
Typically, eucapnia was achieved with f greater than 16 Hz, D = 1 mm, a = 1
G, Pes = Ptr = 4 +/- 2 cmH2O, and VT less than 2 ml. Inverse exponential
relationships were found between PaCO2 and f, a, Pes, and Ptr (exponents:
-0.69, -0.38, -0.48, and -0.54, respectively); PaCO2 decreased linearly
with increased displacement or VT at a fixed frequency (17 +/- 1 Hz). PaO2
was independent of both f and D (393 +/- 78 Torr, mean +/- SD). These data
demonstrate the very small VT, Ptr, and Pes associated with vibration
ventilation. It is clear, however, that mechanisms other then those
described for conventional ventilation and high-frequency ventilation must
be evoked to explain our data. One such possible mechanism is forcing of
flow oscillation between lung regions (i.e., forced pendelluft).
