Journal of Applied Physiology, Vol 65, Issue 1 146-155, Copyright © 1988 by American Physiological Society
Pendelluft and mixing in a single bifurcation lung model during high-frequency oscillation
J. S. Ultman, R. G. Shaw, D. C. Fabiano and K. A. Cooke
Department of Chemical Engineering, Pennsylvania State University, University Park 16802.
A single bifurcation with an adjustable daughter branch compliance ratio
(VR) was used to simultaneously study pendelluft and longitudinal mixing
during flow oscillations at frequencies (f) of 1-15 Hz and amplitudes (VOp)
of 25-150 ml/s. Mixing coefficients (Deff) were determined from the
dispersion of a CO2 bolus centered at the bifurcation point, and pendelluft
volume was computed as a fraction of mother branch tidal volume (PVF) using
measurements of airflow in the daughter branches. Plotted against
frequency, PVF was a bell-shaped curve insensitive to the value of VOp.
When VR = 2, a PVF peak of 0.25 appeared at f = 3 Hz, and when VR = 5, a
PVF peak of 0.75 appeared at f = 4 Hz. After normalization by control
values at VR = 1, Deff curves were also bell shaped, insensitive to the
value of VOp and with peaks appearing at the same frequencies as the PVF
peaks. The normalized Deff peak values were 1.7 when VR = 2 and 4.0 when VR
= 5. The similarities in the PVF and Deff curves imply a direct
relationship between pendelluft and enhanced mixing.
