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Veterinary Research Communications

, Volume 19, Issue 6, pp 517–527 | Cite as

The effects of three models of airway disease on tidal breathing flow-volume loops of thoroughbred horses

  • A. J. Guthrie
  • R. E. Beadle
  • R. D. Bateman
  • C. E. White
Pathology

Abstract

The effects of histamine and methacholine aerosols and of a fixed inspiratory resistance on tidal breathing flow-volume loops (TBFVL) were investigated using 18 unsedated, standing, healthy thoroughbred horses. The data were first analysed using traditional flow-volume loop indices and then reduced using standardized factor scoring coefficients obtained in a previous study in this laboratory using similar experimental techniques. On the basis of resting TBFVL analysis, the degree of pulmonary dysfunction caused by inhalation of histamine and methacholine aerosols with concentrations of 10 and 2 mg/ml, respectively, was similar. The fixed resistance also caused significant changes in the resting spirogram and TBFVL indices, suggesting that this model may prove valuable for further studies involving upper respiratory tract (URT) conditions.

Administration of histamine and methacholine aerosols resulted in significant changes in all factor scores, although most of the observed changes were due to the effects of these aerosols on the respiratory rate. These findings re-emphasize the importance of the effects of respiratory rate on pulmonary mechanics. Application of the resistance resulted in significant changes in factor score 3, the ‘inspiratory’ factor, which lends support to the validity of this model for URT conditions. The close agreement between the factor scores obtained under controlled conditions in this study and in a previous study in this laboratory confirms that the factor analysis used for both of these studies provides an adequate means of reducing TBFVL data obtained from thoroughbred horses.

The large intra- and inter-individual variation observed both with the indices of TBFVL and with the factor scores limits the potential of these variables for detecting individual animals with obstructive airway disease. Re-evaluation of these indices under the stress of exercise may reduce the variability observed in these data and may increase the magnitude of differences between different animals, providing a means of detecting individual animals with subclinical obstructive airway conditions.

Keywords

factor analysis flow-volume loop histamine horse inspiratory resistance methacholine pulmonary function 

Abbreviations

CV

coefficient of variation

ΔPpl,max

maximal intrapleural pressure difference

FVL

flow-volume loop

LRT

lower respiratory tract

Pao

airway opening pressure

Ptp

transpulmonary pressure

TBVFL

tidal breathing flow-volume loop

URT

upper respiratory tract

USPTM

ultrasonic pneumotachometer

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Copyright information

© Kluwer Academic Publishers bv 1995

Authors and Affiliations

  • A. J. Guthrie
    • 1
  • R. E. Beadle
    • 2
  • R. D. Bateman
    • 2
  • C. E. White
    • 2
  1. 1.Department of Veterinary Physiology, Pharmacology and ToxicologyLouisiana State UniversityBaton RougeUSA
  2. 2.Department of Veterinary Clinical Sciences, School of Veterinary MedicineLouisiana State UniversityBaton RougeUSA

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