Journal of Applied Physiology, Vol 46, Issue 5 1011-1015, Copyright © 1979 by American Physiological Society
Influence of expiratory flow rate on "closing volume" measurement
D. P. Osmanliev and P. K. Popov
The influence of expiratory flow rate (VE) on the onset of phase IV was
studied in 15 normal subjects. VE was controlled voluntarily and varied
between 0.2 and 2.5 l/s. All subjects showed significantly higher values
for CV/VC, % at expiratory flow rate of 1.0 and 1.5 l/s, compared to those
estimated at 0.2 l/s. The correlation between CV and volume of flow
limitation (VFL) was also studied. For most of the subjects a considerable
disagreement between the two values at very low VE was found. At higher
flows, however, CV and VFL agreed well. Our results indicate that CV
measurement is markedly influenced by VE in the range 0.2--1.5 l/s. This
finding gives further support to the hypothesis that CV is determined in
part by dynamic flow-limiting properties of the lung as well as by true
airway closure.
