Date of Award

1990

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

First Advisor

Ralph E. Beadle

Abstract

The purpose of the first part of this study was to develop computerized techniques for automation of instrument calibration, data collection and calculation of indices of pulmonary mechanical function in resting and exercising horses. The microcomputer system developed enabled a single trained technician to reliably operate the equipment in an equine pulmonary mechanics laboratory. The first experiment investigated the temporal effects of histamine and methacholine aerosols on indices of pulmonary mechanics derived from the linear equation of motion. Data calculated on a breath-by-breath basis were too variable to be reliably modeled. Following application of averaging techniques, the temporal effects of histamine and methacholine on respiratory rate were the most predictable of all the response variables studied. In experiment two, normal tidal breathing flow-volume loops (TBFVLs) of resting horses were characterized. In excess of 90% of the variance of 10 TBFVL indices were summarized by a factor analysis with three factors. The first factor explained 82% of the total variance and was mainly due to time and volume relationships. Factor 2 was the expiratory flow factor, and explained a further 11% of the variance. The third factor was indicative of the shape of the inspiratory part of the TBFVL and explained 7% of the total variance. The last experiment investigated the effects of three models of obstructive airway disease on TBFVLs. TBFVLs were analyzed using loop shape indices and standardized factor scores. Factor scores were obtained using the standardized factor scoring coefficients determined in experiment two. Under control conditions the factor scores were no different from those obtained in experiment two. Histamine and methacholine inhalation caused significant (P $<$ 0.05) changes in all three of the factor scores. Increased inspiratory resistance caused significant changes (P $<$ 0.05) in the factor score that characterized the inspiratory limb of TBFVLs. The variability of these data implied that the techniques used in these studies were sensitive enough to detect differences between the effects of models of obstructive airway disease in a population of horses, but not to detect individual animals with sub-clinical obstructive airway disease.

Pages

227

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