Title page for ETD etd-07102009-190004

Type of Document Master's Thesis
Author Lee, Laura Caryn
URN etd-07102009-190004
Title Comparative efficacy of three common treatments for equine recurrent airway obstruction.
Degree Master of Science
Department Veterinary Medical Sciences
Advisory Committee
Advisor Name Title
Buechner-Maxwell, Virginia A. Committee Member
Witonsky, Sharon G. Committee Member
Zimmerman, Kurt L. Committee Member
  • Pulmonary Function Testing
  • Airway Inflammation
  • Asthma
  • Equine Recurrent Airway Obstruction (RAO)
  • Equine Heaves
  • Allergy
  • Dexamethasone
  • Environmental Modification
  • Airway Neutrophilia
  • Bronchoalveolar Lavage Fluid
Date of Defense 2009-04-17
Availability unrestricted
Objective – evaluate horses with acute airway obstruction using three treatment regimens: tapering doses of dexamethasone (DEX), environmental modification (ENV), and a combination of both treatments (DEX + ENV) by analyzing clinical parameters, pulmonary function testing, bronchoalveolar lavage fluid (BALF) cytology and BALF cell expression of the cytokines IFN-γ and IL-4

Animals – 6 horses with recurrent airway obstruction (RAO)

Procedures – Clinical examination, pulmonary function test, and collection of BALF prior to treatment and during 22 day treatment period

Hypothesis - Alterations in clinical parameters, pulmonary function and airway inflammation in acute equine RAO will return to remission values by treating with DEX, ENV or DEX + ENV

Results – All horses demonstrated clinical disease, reduced pulmonary dynamic compliance (Cdyn) and an increased maximum change in pleural pressures (ΔPplmax) when in a challenge environment. All treatments improved clinical parameters, ΔPplmax and Cdyn. BALF cytology during an RAO crisis demonstrated neutrophilic inflammation. ENV or DEX + ENV resulted in a significant decrease in airway neutrophilia that was maintained throughout the treatment period. In contrast, treatment with DEX caused a reduction in airway neutrophilia initially followed by a rebound neutrophilia as the period between administrations of dexamethasone (0.05mg/kg) was increased to 72 hours. The rebound neutrophilia was not accompanied by equivalent deterioration in clinical parameters or pulmonary function.

Conclusions – Environmental modification is important in the management of RAO horses. Treatment of clinical RAO with a decreasing dosage protocol of corticosteroids in the absence of environmental modification results in the persistence of airway inflammation without recrudescence of clinical disease.

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