CHARACTERIZATION OF NORMAL TIDAL BREATHING FLOW-VOLUME LOOPS FOR THOROUGHBRED HORSES

The purpose of this study was to characterize the normal equine tidal breathing flow-volume loop (TBFVL). The study was performed using 18 h ealthy Thoroughbred horses. TBFVLs constructed from data collected fro m resting horses had a typical biphasic inspiratory and expiratory pha se. The interindividual variability of the indices used to describe TB FVLs was in the range 16-32%, which is comparable to the variability o f other measures of equine pulmonary mechanics. The large variability of these data probably limits the value of resting TBFVL indices for d etecting subclinical respiratory conditions in individual horses. Fact or analysis of these data revealed that in excess of 90% of the varian ce of the initial response variables could be explained in terms of th ree common factors. Varimax rotation of these three common factors pro vided three subsequent factors that were readily identifiable as (1) a factor describing the time-volume relationships of TBFVLs, responsibl e for 81% of the total variance, (2) a factor explaining the expirator y portion of the TBFVL, explaining 12% of the variance, and (3) a fact or describing the inspiratory portion of the loops, responsible for th e remaining 7% of the variance. The analysis also provided standardize d factor scoring coefficients for use in subsequent studies using simi lar experimental techniques.