Journal of Applied Physiology, Vol 70, Issue 2 650-657, Copyright © 1991 by American Physiological Society
Contribution of large airway to the input impedance of the respiratory system
J. P. Teeter, G. M. Saidel and J. M. Fouke
Department of Biomedical Engineering, Case Western Reserve University, Cleveland, Ohio 44106.
To evaluate the contribution of the large airway to total respiratory
impedance, we develop a one-dimensional model of pressure and flow in these
airways by coupling conservation of mass and momentum equations with the
geometric information obtained by the acoustic reflection technique. We use
this model to calculate the impedance of the respiratory system distal to
the carina from impedance data estimated at the airway opening by the
forced oscillation technique. Simulations show that the real part of the
impedance distal to the carina is uniformly decreased from the impedance at
the airway opening, indicating a resistive loss, while the imaginary part
is increased as a function of frequency. We estimate parameter values for a
six-parameter two-compartment lung model and for a three-parameter
reduction of this model before and after the application of the upper
airway data to the impedance spectrum. Although compliance terms seem to be
minimally affected by the manipulation of the data, resistance and
inertance terms are influenced in a fashion that suggests that the
resistive contribution of the upper airway to total respiratory impedance
is significant. Furthermore it appears that the elastic nature of the walls
of the upper airway also impact on estimates of total respiratory impedance
at the airway opening.
