Journal of Applied Physiology, Vol 50, Issue 1 15-20, Copyright © 1981 by American Physiological Society
Sensitivity of forced expiration indices to induced changes in peripheral airway resistance
J. L. Racineux, R. Peslin and B. Hannhart
To assess the actual sensitivity of forced expiration indices to changes in
the resistance of peripheral airways, maximal expiratory flow-volume curves
were obtained in 30 normal subjects breathing air and breathing an
O2-Ne-SF6 gas mixture having the same density as air but a 45% larger
viscosity. The measurements were made using a bag-in-box system to
circumvent calibration problems, and the data were processed digitally.
Besides the usual forced expiration indices, slope ratios, as described by
Mead (J. Appl. Physiol.: Respirat. Environ. Exercise Physiol. 44: 156-165,
1978), and transit time indices were also computed. Breathing the viscous
mixture, the largest changes were seen with the slope ratio measured at 60%
forced vital capacity, followed by other slope ratios, the standard
deviation of transit times, and maximal flows at low lung volumes. However,
when the data were compared using the t test for paired measurements, the
most significant changes were found with the forced expiratory volumes at 1
and 2 s, due to their low within-subject variability. These indices may
therefore by considered as the most suitable for detecting changes in
individuals.
