Journal of Applied Physiology, Vol 50, Issue 3 672-678, Copyright © 1981 by American Physiological Society
A new method for computer-assisted determination of airways resistance
P. J. Chowienczyk, P. J. Rees, J. Payne and T. J. Clark
Conventional methods for determining airways resistance, based on the
recording of pressure and flow as X-Y displays, may yield inconsistent
results because airways resistance is only one of a number of factors
determining the shape of such displays. The temporal behavior of alveolar
pressure and flow during panting suggests that the relationship between
pressure and flow should be formulated in terms of differential equations.
An equation is postulated to include terms characterizing resistance, gas
inertance, and the behavior of the lungs as a number of parallel
compartments with time constants that may be different. A simple algorithm
allows these terms to be deduced from measured pressure and flow signals.
Measurements obtained using the new method correlate well with those
obtained using conventional methods. Variation of specific airways
conductance is significantly reduced when compared with values obtained by
conventional methods. Measured values for inertance agree well with
theoretically predicted values.
