Comparative study of intra-airway gas transport by alternative
modes of ventilation.
Gavriely, Noam, Donald P. Gaver, Iii, Julian Solway, and James B.
Grotberg.
Department of Physiology and Biophysics, Bruce Rappaport Faculty of
Medicine and the Rappaport Family Institute for Research in the
Medical Sciences, Technion, Israel Institute of Technology, Haifa,
Israel; Department of Anesthesia, Northwestern University Medical
School, Chicago, IL, 60611; Department of Biomedical Engineering,
Tulane University, New Orleans, LA, 70118; Section of Pulmonary and
Critical Care Medicine, University of Chicago, Chicago, IL, 60637;
and (5) Biomedical Engineering Department, McCormick School of
Engineering and Applied Science, Northwestern University, Evanston,
IL, 60208;
APStracts 2:0313A, 1995.
The effectiveness of three alternative modes of ventilation: high
frequency ventilation (HFV), constant flow ventilation (CFV), and
high frequency external vibration ventilation (HFVV) was compared.
Local intra-airway gas transport was measured with catheters placed
in the distal trachea and in bronchi located 5.5, 9 and 11 cm from
the carina. A new bolus dispersion method was devised to measure the
local effective diffusivities (Deff) induced by these modes of
ventilation and by cardiogenic oscillations, relative to molecular
diffusivity (Dmol). Mixing induced by cardiogenic oscillations was
7+/-2 to 26+/-4 fold greater than by molecular diffusion alone.
Intra- airway transport by CFV, applied at 3 flow rates: 0.3, 1.0 and
3.0 l x min-1 x kg-1, was most effective in the trachea, but fell
sharply in the more peripheral airways. Local transport by HFVV, at
frequency of 22 Hz and vertical amplitude of 0.4 cm, was most
effective in the periphery (Deff=793 x Dmol), while the effectiveness
of transport by HFV, applied with 10 and 20 ml at 22 Hz, was evenly
distributed. Doubling the HFV oscillatory volume caused a 4.5+/-2.7
fold increase in Deff/Dmol. Combining HFVV with CFV at 0.3 l x min-1
x kg-1 induced transport rates that were 187 to 2034 fold greater
than by molecular diffusion alone in the bronchi and a higher
relative transport (due to convection) in the trachea. We conclude
that the combination of HFVV with low flow CFV provides high rate of
intra-airway transport with minimal mechanical perturbations to the
pulmonary system.
Received 27 December 1994; accepted in final form 23 June 1995.
APS Manuscript Number A1344-4.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 18 July 1995.