Journal of Applied Physiology, Vol 47, Issue 6 1325-1331, Copyright © 1979 by American Physiological Society
Estimating central and peripheral respiratory resistance: an alternative analysis
A. S. Slutsky and J. M. Drazen
Pimmel et al (J. Appl. Physiol.: Respirat. Environ. Exercise Physiol. 45:
375--380, 1978) recently presented an analysis of the frequency dependence
of respiratory resistance (Rrs) based on a simple electrical analog of the
respiratory system that allows estimation of the central (Rc) and
peripheral (Rp) components of Rrs. The method by which they determine these
parameters from the experimental data is based on a number of unproven
assumptions. Using the same electrical analog, we present an analysis that
allows calculation of these parameters, as well as the corner frequency of
the network (f1), without need for similar assumptions. Our technique is
based on fitting the resistances (RTh) measured over a range of frequencies
(f) to the exact solution of the network given by RTh = Rc + Rpf1(2)/f2 +
f1(2)). Using the transformation X = 1/(f2 + f1(2), the equation becomes a
linear relationship between RTh and X allowing the resistances to be
determined by linear regression. Reanalysis of Pimmel et al.'s data
demonstrated that the assumptions of a constant f1, and the equivalence of
RTh at 0 Hz to RTh at 1 Hz in invalid under certain conditions. Thus, if
one is to use the electrical analog to partition Rrs into its central and
peripheral components, one should use the analytic approach suggested here
that does not rely on these assumptions.
