Journal of Applied Physiology, Vol 48, Issue 5 903-910, Copyright © 1980 by American Physiological Society
Computer measurement of dynamic compliance: technique and reproducibility in man
N. J. Douglas, P. K. Wraith, H. M. Brash, J. Millar, M. F. Sudlow and D. C. Flenley
A computer program was developed to calculate the frequency dependence of
dynamic compliance (Cdyn) using continuous data analysis. Cdyn was measured
repeatedly in eight normal human subjects over a 2-yr period. Comparison
with Cdyn results measured manually showed that the computer program
improved 10-fold the ratio of variance within subjects to between subjects
of the compliance at specific frequencies, but there was only slight
improvement in indices of the slope of the frequency dependence of
compliance. We suggest that the absolute compliance at specific frequencies
merits further consideration as a pathophysiological measurement and that,
if the frequency dependence of compliance continues to be used,
standardization of its calculation should be applied and the wide normal
range should be more widely appreciated. Measurements of Cdyn in subjects
breathing 80% helium-20% oxygen confirm that inertia is insignificant when
breathing with tidal volumes of less than 500 ml and frequency of less than
1.5 Hz.
