Journal of Applied Physiology, Vol 79, Issue 1 243-250, Copyright © 1995 by American Physiological Society
Intra-airway gas transport during high-frequency chest vibration with tracheal insufflation in dogs
N. Gavriely, D. M. Eckmann and J. B. Grotberg
Department of Anesthesia, Northwestern University Medical School, Chicago 60611, USA.
High-frequency external chest vibration with tracheal insufflation
(high-frequency vibration ventilation) has previously been shown to be an
effective mode of artificial ventilation in experimental animals. To
investigate the intra-airway gas mixing during high-frequency vibration
ventilation (frequency 30 Hz, amplitude 0.4 cm), we used an analysis of the
single-breath washout curve that gives the vibration-induced mixing
coefficient distribution relative to the no-vibration situation. Data from
four anesthetized dogs were collected during constant-flow insufflation at
six rates (0.05-0.4 l.min-1.kg-1), at three insufflation durations (2, 4,
and 7 s), and with the insufflation catheter outlet at three positions
(carina, trachea, and a bronchus) while the vibration was on and off.
Vibration enhanced intra-airway gas mixing 14.1 +/- 3.9-fold, with the peak
of the enhancement distribution located 125 +/- 29 ml from the airway
opening and a distribution width of 121 +/- 29 ml. As insufflation flow
increased, the position of the peak enhancement shifted toward the alveolar
zone and diminished in peak amplitude. Changing the insufflation duration
and the catheter position did not affect the intra-airway mixing induced by
vibration. External chest vibration causes a substantial increase of
intra-airway gas mixing, bringing alveolar gas to central airways. This
leads to overall increased pulmonary gas transport when fresh gas is
insufflating the tracheal carina area.
