Frequency dependence of forced oscillatory respiratory mechanics in
horses with heaves.
Young, S. S., D. Tesarowski[acute]a, and L. Viel.
Department of Clinical Studies, University of Guelph, Guelph,
Ontario, Canada N1G 2W1
APStracts 3:0497A, 1996.
The effects of measurement frequency on respiratory mechanics was
investigated in 6 horses with reversible allergic airway disease.
Total respiratory impedance was measured at 1.5, 2, 3 and 5 Hz using
the forced oscillation technique with the horses in remission, after
acute antigenic challenge producing clinical heaves, and with heaves
but after the administration of 2mg fenoterol by inhalation. The
slopes of the magnitude (|Z|) and real part (R) of total respiratory
impedance over the frequency range 1.5-3Hz changed significantly
after antigenic challenge and fenoterol. The ratio of R at 2Hz to R
at 3Hz, however, discriminated better between the three conditions.
Compliance and resonant frequency (calculated using a 3 element
model) changed significantly after antigenic challenge and fenoterol
but inertance did not. We concluded that horses with heaves showed
frequency dependence of R and |Z| at frequencies up to 3 Hz, and that
parameters derived from a 3 element model were useful indicators of
small airway obstruction in the horse.
Received 20 June 1996; accepted in final form 22 October 1996.
APS Manuscript Number A573-6.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 13 November 1996